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1.  Prevalence of asthma symptoms among adults aged 20–44 years in Canada 
Reported prevalence rates of asthma vary within and between countries around the world. These differences suggest environmental factors in addition to genetic factors in the cause of the disease and may provide clues for preventive strategies. We examined the variability of asthma-related symptoms and medication use among adults in 6 sites across Canada (Vancouver, Winnipeg, Hamilton, Montreal, Halifax and Prince Edward Island) and compared our findings with those from sites that had participated in a recent European survey.
We used the same sampling strategy and standardized questionnaire as those used in the European Community Respiratory Health Survey (ECRHS). The 6 Canadian sites were selected to represent different environments with respect to climate, air pollution and occupational exposure. Community-based samples of 3000 to 4000 people aged 20–44 years were randomly selected in each site. Subjects were asked to complete the questionnaire by mail between March 1993 and November 1994. Prevalence rates (and 95% confidence intervals [CIs]) of asthma symptoms, self-reported asthma attacks and use of asthma medication were compared across the Canadian sites and with sites that had participated in the ECRHS.
The overall response rate of those selected to receive the questionnaire was 86.5% (range 74.5%–92.8%). The prevalence rates of most asthma symptoms varied significantly among the Canadian sites. For instance, 21.9% (Montreal) to 30.4% (Halifax) of the men and 24.0% (Vancouver) to 35.2% (Halifax) of the women reported wheezing in the year before the survey. Depending on the site, 4.4% to 6.3% of the men and 5.2% to 9.5% of the women reported an asthma attack in the last year, and 4.0% to 6.1% of the men and 4.9% to 9.7% of the women were currently using asthma medication. Prevalence rates of symptoms, asthma attacks and medication use did not change with age, but they were higher among women than among men. Compared with the results from the ECRHS sites, those from the Canadian sites were among the highest.
Significant variation in the prevalence of asthma symptoms, asthma attacks and use of asthma medication between Canadian sites and international sites suggests environmental influences. Different combinations of factors in different sites may be responsible for the high prevalence rates and should be the subject of further research to guide clinical management and public health intervention.
PMCID: PMC80927  PMID: 11314453
2.  Factors associated with difference in prevalence of asthma in children from three cities in China: multicentre epidemiological survey  
BMJ : British Medical Journal  2004;329(7464):486.
Objective To determine the factors associated with difference in prevalence of asthma in children in different regions of China.
Design Multicentre epidemiological survey.
Setting Three cities in China.
Participants 10 902 schoolchildren aged 10 years.
Main outcome measures Asthma and atopic symptoms, atopic sensitisation, and early and current exposure to environmental factors.
Results Children from Hong Kong had a significantly higher prevalence of wheeze in the past year than those from Guangzhou and Beijing (odds ratio 1.64, 95% confidence interval 1.35 to 1.99). Factors during the first year of life and currently that were significantly associated with wheeze were cooking with gas (odds ratio 2.04, 1.34 to 3.13), foam pillows (2.58, 1.66 to 3.99), and damp housing (1.89, 1.26 to 2.83). Factors protecting against wheeze were cotton quilts and the consumption of fruit and raw vegetables.
Conclusion Environmental factors and diet may explain the differences in prevalence of asthma between children living in different regions of China.
PMCID: PMC515199  PMID: 15331473
3.  Self-reported prevalence of childhood allergic diseases in three cities of China: a multicenter study 
BMC Public Health  2010;10:551.
Several studies conducted during the 1990s indicated that childhood allergic diseases were increasing worldwide, but more recent investigations in some Western countries have suggested that the trend is stabilizing or may even be reversing. However, few data are available on the current status of allergic disease prevalence in Chinese children. The aim of the present study was to investigate the prevalence rates of asthma, allergic rhinitis, and eczema in children of three major cities of China, to determine the status of allergic diseases among Chinese children generally, and to evaluate the prevalence of allergic diseases in children of different ages.
We conducted a cross-sectional survey between October 2008 and May 2009 in three major cities of China (Beijing, Chongqing, and Guangzhou) to evaluate the prevalence rates of childhood allergic diseases including asthma, allergic rhinitis, and eczema, using a questionnaire of the International Study of Asthma and Allergies in Childhood (ISAAC) group. A total of 24,290 children aged 0-14 years were interviewed, using a multi-stage sampling method. To acquire data on children aged 3-14 years, we visited schools and kindergartens. To access children too young to attend school or kindergarten, we extended our survey to community health service centers. Each questionnaire was completed by a parent or guardian of a child after an informed consent form was signed.
Of the 24,290 children in our study, 12,908 (53.14%) were males and 11,382 (46.86%) females; 10,372 (42.70%) were from Beijing, 9,846 (40.53%) from Chongqing, and 4,072 (16.77%) from Guangzhou. Our survey indicated that in Beijing, Chongqing, and Guangzhou, the prevalence rates of asthma were 3.15%, 7.45%, and 2.09%, respectively; the rates of allergic rhinitis were 14.46%, 20.42%, and 7.83%; and the rates of eczema were 20.64%, 10.02%, and 7.22%. The prevalence of allergic diseases varied with age. Asthma was relatively less common both in children aged under 2 years, and in those aged 9 years or more, in each of the three cities. The prevalence of allergic rhinitis was also lower in children younger than 2 years. The prevalence of eczema fell with age.
A marked increase in the prevalence rates of allergic diseases in China (compared with earlier data) was evident. Further studies exploring the precise causes of this increase are warranted.
PMCID: PMC2944377  PMID: 20836838
4.  The problem of obesity among adolescents in Hong Kong: a comparison using various diagnostic criteria 
BMC Pediatrics  2008;8:10.
Obesity is now a global epidemic. In this study, we aimed to assess the rates of obesity using several major diagnostic criteria in Chinese school adolescents in Hong Kong.
This is a cross-sectional study. Using a computer-generated coding system, we randomly selected schools from different geographical regions in Hong Kong to obtain a representative sample. Subjects aged 11–18 years of age were randomly selected from different class of the schools. Their rates of obesity according to four different international and local criteria were compared [International Obesity Task Force (IOTF) 2000 criterion; the Group of China Obesity Task Force (COTF) 2004 criterion; Centers for Disease Control and Prevention (CDC) 2000 Growth Charts and the Hong Kong Growth Survey (HKGS) charts in 1993].
Of the 2098 adolescents [982 (46.8%) boys and 1116 (53.2%) girls], the mean age (± SD) was 15.1 ± 1.8 years (range: 11–18 years; median: 15.0 years). The crude rates of obesity were similar based on IOTF, COTF or CDC criteria (boys: 3.9–6.0%, girls: 1.8–3.7%), however, the rate increased to 11–27% if the HKGS charts were used. Obesity rate varied markedly according to age. It decreased from 8–10% among those aged 12–13 years to 2–4% among those aged 17–18 years.
The prevalence of obesity in Hong Kong adolescents using various diagnostic criteria were similar except for the 1993 HKGS criteria, which gave an exceeding high figure. Using the IOTF, COTF or CDC criteria, the adolescent obesity in Hong Kong varied from 1.8% to 6.0%.
PMCID: PMC2276189  PMID: 18315886
5.  Repeatability of self-report measures of physical activity, sedentary and travel behaviour in Hong Kong adolescents for the iHealt(H) and IPEN – Adolescent studies 
BMC Pediatrics  2014;14:142.
Physical activity and sedentary behaviour are important contributors to adolescents’ health. These behaviours may be affected by the school and neighbourhood built environments. However, current evidence on such effects is mainly limited to Western countries. The International Physical Activity and the Environment Network (IPEN)–Adolescent study aims to examine associations of the built environment with adolescent physical activity and sedentary behaviour across five continents.
We report on the repeatability of measures of in-school and out-of school physical activity, plus measures of out-of-school sedentary and travel behaviours adopted by the IPEN – Adolescent study and adapted for Chinese-speaking Hong Kong adolescents participating in the international Healthy environments and active living in teenagers–(Hong Kong) [iHealt(H)] study, which is part of IPEN-Adolescent.
Items gauging in-school physical activity and out-of-school physical activity, and out-of-school sedentary and travel behaviours developed for the IPEN – Adolescent study were translated from English into Chinese, adapted, and pilot tested. Sixty-eight Chinese-speaking 12–17 year old secondary school students (36 boys; 32 girls) residing in areas of Hong Kong differing in transport-related walkability were recruited. They self-completed the survey items twice, 8–16 days apart. Test-retest reliability was assessed for the whole sample and by gender using one-way random effects intra-class correlation coefficients (ICC). Test-retest reliability of items with restricted variability was assessed using percentage agreement.
Overall test-retest reliability of items and scales was moderate to excellent (ICC = 0.47–0.92). Items with restricted variability in responses had a high percentage agreement (92%-100%). Test-retest reliability was similar in girls and boys, with the exception of daily hours of homework (reliability higher in girls) and number of school-based sports teams or after-school physical activity classes (reliability higher in boys).
The translated and adapted self-report measures of physical activity, sedentary and travel behaviours used in the iHealt(H) study are sufficiently reliable. Levels of reliability are comparable or slightly higher than those observed for the original measures.
PMCID: PMC4060092  PMID: 24903156
Adolescents; Physical activity; Sedentary behaviour; Self-reports; Repeatability; Multi-country study; China
6.  Asthma, atopy and tuberculin responses in Chinese schoolchildren in Hong Kong 
Thorax  2001;56(10):770-773.
BACKGROUND—The prevalence rates of asthma and other atopic disorders have increased steadily in many developed countries over the past few decades. Recent epidemiological and animal studies have suggested that BCG vaccination might be beneficial in reducing the subsequent development of atopy. This study investigates the relationship between asthma, allergic symptoms, atopy, and tuberculin response in Chinese schoolchildren who received BCG vaccination at birth.
METHODS—A total of 3110 schoolchildren aged 10 years were recruited for the Hong Kong arm of the phase II International Study of Asthma and Allergies in Childhood. Of the 2599 children born in Hong Kong and vaccinated with BCG after birth, 2201 had tuberculin testing performed at a mean (SD) age of 8.4 (1.4) years. A random subsample of 980 children was also recruited for skin prick testing.
RESULTS—The prevalence rates of asthma ever, wheeze ever, current wheeze, current rhinoconjunctivitis, and current flexural eczema were not significantly different between tuberculin positive and negative subjects. The mean (SE) tuberculin response was 3.4 (0.2) mm in atopic subjects and 3.3 (0.2) mm in non-atopic subjects (difference not significant). Logistic regression analyses did not reveal any significant relationship between asthma ever, current wheeze, atopy, and positive tuberculin responses.
CONCLUSIONS—This study did not find any relationship between asthma, allergic symptoms, atopy, and positive tuberculin reactivity in Chinese schoolchildren vaccinated with BCG at birth.

PMCID: PMC1745922  PMID: 11562515
7.  Screening for asthma in Cantonese-speaking immigrant children 
BMC Public Health  2005;5:48.
Asthma prevalence among Chinese immigrant children is poorly understood and attempts to screen these children have produced varied outcomes. We sought to learn how to improve screening for asthma in Chinese immigrant children.
Children (n = 152) were administered the Brief Pediatric Asthma Screen in either Cantonese or English, they then viewed and reacted to a video showing people wheezing and subsequently took a pulmonary function test.
The diagnosed asthma prevalence for our study population was 27.0%, with another 5.3% having possible undiagnosed asthma. Very few children had spirometry findings below normal. In multivariate analysis, being native born (p = 0.002) and having a family history of asthma (p = 0.003) were statistically associated with diagnosis of asthma. After viewing the video, 35.6% of respondents indicated that the images differed from their conception of wheezing. Of four translations of the word "wheeze" no single word was chosen by a majority.
Our findings suggest that asthma diagnoses are higher for Chinese children who were born in the US suggesting that desegregation of data might reveal at risk subpopulations. Care needs to be taken when diagnosing asthma for Cantonese speakers because of the centrality of the word wheeze and the challenges of translation.
PMCID: PMC1168903  PMID: 15904513
8.  Overweight, family history of diabetes and attending schools of lower academic grading are independent predictors for metabolic syndrome in Hong Kong Chinese adolescents 
Archives of Disease in Childhood  2006;92(3):224-228.
Overweight and metabolic syndrome (MES) are emerging in both adult and paediatric populations.
To study the prevalence of and associated risk factors for the MES, using the National Cholesterol Education Program definition, among Hong Kong Chinese adolescents studying in secondary schools.
This was a cross‐sectional, population‐based study. A sample of 2115 Chinese adolescents was randomly selected from 14 secondary schools throughout Hong Kong. Data on anthropometric parameters, fasting blood and urine samples were collected in the school setting. Information regarding the adolescent's family history of diabetes, perinatal history, socioeconomic status and school grading was evaluated.
The prevalence of MES was 2.4% (95% confidence interval (CI) 1.8 to 3.1), with no significant difference between boys (2.9%) and girls (2%). The prevalence of various components of MES was 32.2% (30.2 to 34.2) for hypertension, 10.9% (9.6 to 12.2) for increased triglyceride, 9.0% (7.8 to 10.2) for central adiposity, 2.4% (1.7 to 3) for low high‐density lipoprotein cholesterol and 0.3% (0.1 to 0.6) for impaired fasting glucose. On multivariate analysis, overweight (odds ratio 32.2; 95% CI 13.2 to 78.4), positive family history of diabetes (4.3; 1.3 to 14.1) and studying at schools of lower academic grading (5.5; 2.2 to 13.7) were found to be independent risk factors for MES.
A comparable prevalence of MES (2%) is observed in our study group Chinese adolescent girls and in US girls (2.1%), but a lower prevalence in Chinese boys (2.9%) than in US boys (6.1%). In our study, 41.8% harbour at least one component of the syndrome. Both families and schools should be alerted to this growing epidemic.
PMCID: PMC2083404  PMID: 17088339
9.  Adolescent health and adaptation in Canada: examination of gender and age aspects of the healthy immigrant effect 
A longstanding and widely held assumption is that immigrants suffer from ill health and adaptation problems. Yet recent studies show that immigrants report the same or better state of health compared to their native-born counterparts. This phenomenon, known as the healthy immigrant effect, has been found in studies of specific health conditions of adults. The present study focuses instead on adolescents and extends its examination of the healthy immigrant effect, measuring both health and adaptation.
Using data from population samples in the Canadian Community Health Survey (2007), foreign-born immigrant adolescents (n = 920) were compared to non-immigrant adolescents (n = 13,572) for their self-report to questionnaire items for health (general health, mental health, chronic illnesses with psychosomatic symptoms, and psychological illnesses) and adaptation (daily life stress, life satisfaction, and sense of belonging). Adolescents’ gender, age, and length of residence were analyzed for the effects.
Immigrant adolescents were better than non-immigrant peers on the four health measures, and did not differ from non-immigrants on the three adaptation measures despite having less household income and more family members in the household. Immigrant girls exhibited more resilient adaptability, while young immigrant boys and older non-immigrant girls displayed some potential vulnerability. Length of residence, on the other hand, did not contribute to differences for the health and adaptation of immigrant adolescents.
The healthy immigrant effect was confirmed in a community population sample of adolescents in Canada. Foreign-born immigrant adolescents experience better health, as well as good adaptation equal to their native-born peers. These outcomes call for further research on sustaining good health and adaptation of the immigrant population, in particular by providing age-related effective services and prevention strategies.
PMCID: PMC4243294  PMID: 25394371
Adolescents; Health and adaptation; Healthy immigrant effect; Acculturation
10.  Chinese herbal medicine and acupuncture. How do patients who consult family physicians use these therapies? 
Canadian Family Physician  1998;44:1009-1015.
OBJECTIVE: To determine how a population of Chinese patients consulting family physicians in Vancouver use traditional Chinese medicine (TCM), specifically Chinese herbal medicine and acupuncture. DESIGN: Bilingual survey (English and Chinese). SETTING: Four family practices with predominantly Chinese patients in metropolitan Vancouver. PARTICIPANTS: The 932 patients or family members who visited one of the practices. MAIN OUTCOME MEASURES: Demographic characteristics; frequency and reason for visiting a family physician, Chinese herbalist, or acupuncturist; choice of practitioner if affected by one of 16 common conditions. RESULTS: The study population was mostly Chinese and immigrant to Canada. Chinese herbal medicine was currently used by 28% (262/930) of respondents (more than one visit in the last year), and another 18% (172/930) were past users. Acupuncture was currently used by 7% (64/927) and had been used in the past by another 8% (71/927). Use of Chinese herbal medicine varied significantly (P < .01) according to age, sex, immigrant status, and ethnicity. Acupuncture use varied significantly only by age. The main reasons for consulting Chinese herbalists were infection (41%, 157/382), respiratory problems (11%, 42/382), and rheumatologic problems (10%, 38/382), whereas acupuncturists were consulted almost exclusively for rheumatologic problems (80%, 45/56). CONCLUSIONS: Using TCM in conjunction with visiting family physicians was very popular among this predominantly Chinese study population. Patients with acute conditions, such as influenza, consulted both their family physicians and Chinese herbalists in quick succession. On the other hand, those suffering from more chronic conditions, such as rheumatologic diseases, were more likely to start using TCM after repeated visits to their family physicians.
PMCID: PMC2277654  PMID: 9612586
11.  Cardiovascular risk factors, diet and lifestyle among European, South Asian and Chinese adolescents in Canada 
Paediatrics & Child Health  2012;17(1):e1-e6.
The authors previously reported that adult South Asian immigrants to Canada have an increased risk of cardiovascular disease (CVD) compared to their European and Chinese counterparts. It is unknown whether these ethnic differences also exist among adolescents, and whether they are related to diet and lifestyle. The objective of the present study was to assess the prevalence of CVD risk factors among apparently healthy adolescents in the three largest ethnic population groups in Canada (European, South Asian and Chinese).
A cross-sectional study among secondary school students in the Greater Toronto Area was undertaken. A total of 203 adolescents from 62 GTA secondary schools were recruited (48% Europeans, 35% Chinese and 18% South Asians) with a mean age of 17.3±1 years; 72% were female.
Similar to adults, South Asian adolescents have increased rates of CVD risk factors compared with their European and Chinese peers, including higher prevalence of low high-density lipoprotein levels (P=0.001), high triglycerides (P=0.006) and high triglyceride/high-density lipoprotein levels (P<0.001), despite no significant differences in dietary intake among the ethnic groups. European adolescents had higher rates of self-reported intensity of physical activity (P=0.002) than their Chinese or South Asian peers.
Similar to adult data, South Asian adolescents have comparably higher rates of CVD risk factors compared with their European or Chinese peers, which could partly be attributed to lower physical activity in South Asian adolescents. Whether the findings in these selected samples of healthy adolescents can be generalized to their respective populations requires further validation.
PMCID: PMC3276533  PMID: 23277758
Adolescents; Cardiovascular disease; Ethnicity; Risk factors
12.  Associations between pre-pregnancy obesity and asthma symptoms in adolescents 
The high prevalence of children's asthma symptoms, worldwide, is unexplained. We examined the relation between maternal pre-pregnancy weight and body mass index (BMI), and asthma symptoms in adolescents.
Data from 6945 adolescents born within the Northern Finland Birth Cohort 1986 were used. Prospective antenatal and birth outcome data, including maternal pre-pregnancy weight and BMI, and asthma symptoms in adolescent offspring at age 15–16 years, were employed. Logistic regression analyses were performed to examine the associations between relevant prenatal factors and asthma symptoms during adolescence.
Current wheeze (within the past year) was reported by 10.6% of adolescents, and physician-diagnosed asthma by 6.0%. High maternal pre-pregnancy BMI was a significant predictor of wheeze in the adolescents (increase per kilogram per square metre unit; 2.7%, 95% CI 0.9 to 4.4 for ever wheeze; 3.5%, 95% CI 1.3 to 5.8 for current wheeze), and adjusting for potential confounders further increased the risk (2.8%, 95% CI 0.5 to 5.1; 4.7%, 95% CI 1.9 to 7.7, respectively). High maternal pre-pregnancy weight, in the top tertile, also significantly increased the odds of current wheeze in the adolescent by 20% (95% CI 4 to 39), and adjusting for potential confounders further increased the risk (OR=1.52, 95% CI 1.19 to 1.95). Results were similar for current asthma. Furthermore, these significant associations were observed only among adolescents without parental history of atopy but not among those with parental history of atopy.
The association demonstrated here between maternal pre-pregnancy overweight and obesity, and asthma symptoms in adolescents suggests that increase in asthma may be partly related to the rapid rise in obesity in recent years.
PMCID: PMC3412048  PMID: 21844604
Asthma; wheeze; prevalence; adolescent; maternal pre-pregnancy weight; BMI; obesity
13.  Caesarean sections and risk of wheezing in childhood and adolescence: data from two birth cohort studies in Brazil 
Clinical and Experimental Allergy  2011;41(2):218-223.
There is evidence from two meta-analyses that children born through caesarean section (C-section) may have an increased risk of developing asthma compared with those born through vaginal delivery.
To evaluate the association between mode of delivery and wheezing (current and persistent) in childhood and adolescence, in two birth cohort studies in Brazil.
The outcome variable was based on the International Study of Allergy and Asthma questionnaire, which collects information about wheezing within the 12 months before the interview. Persistent wheezing was defined when it was present in more than one follow-up at different ages, in the 1993 cohort. The questions were asked to mothers when children were aged 4 years (1993 and 2004 cohorts) and directly to cohort participants at 11 and 15 years (1993 cohort). Mode of delivery was collected by the research team of each cohort when children were born.
Response rates in the last follow-up visit of the 1993 and 2004 cohorts were 85% and 92%, respectively. The prevalence of current wheezing increased from 20% to 28% at 4 years from 1993 to 2004; at 11 and 15 years, the prevalence was around 14% and 12%, in the 1993 cohort. The proportion of C-sections increased from 30.5% to 45% between 1993 and 2004. In each cohort, the prevalence of current wheezing was similar among children born through vaginal and C-section. The risk for persistent wheezing in the 1993 cohort was higher among girls born through C-section than boys.
Despite the increase in the proportion of C-section in two cohorts in Southern Brazil, we found no evidence of an association between mode of delivery and the subsequent risk of wheezing. Among girls, although there was no statistical significance, the risk was higher for those born by C-section, especially regarding persistent wheezing.
PMCID: PMC3505367  PMID: 20840395
adolescent; caesarean section; child; cohort studies; current wheezing; developing countries; epidemiology; persistent wheezing
14.  Determinants of changes in dietary patterns among Chinese immigrants: a cross-sectional analysis 
Chinese individuals who have immigrated to a Western country initially tend to have a lower risk of cardiovascular disease (CVD) compared to people who are already living there. Some studies have found, however, that CVD risk increases over time in immigrants and that immigration to a western country is associated with changes in dietary patterns. This could have unfavourable effects on the risk of CVD. There is limited knowledge on the food patterns, awareness and knowledge about healthy nutrition among Chinese immigrants. The objective for this study is to explore changes in food patterns, and levels of awareness and knowledge of healthy nutrition by length of residence among Chinese immigrants to Canada.
120 Chinese individuals born in China but currently living in Canada completed an assessment on socio-demographic characteristics, changes in dietary patterns and variables of awareness and knowledge about healthy foods. With ordinal logistic regression the associations between the quartiles of length of residence and dietary patterns, variables of awareness and knowledge about healthy foods were explored, adjusting for age, sex, education and body mass index.
More than 50% of the participants reported increasing consumption of fruits and vegetables, decreasing the use of deep-frying after immigration. Increased awareness and knowledge about healthy foods was reported by more than 50% of the participants. Ordinal regression indicated that Chinese immigrants who lived in Canada the longest, compared to Chinese immigrants who lived in Canada the shortest, consumed significant greater portion sizes (OR: 9.9; 95% CI: 3.11 - 31.15), dined out more frequently (OR: 15.8; 95% CI: 5.0 - 49.85), and consumed convenience foods more often (OR: 3.5; 95% CI: 1.23 - 10.01).
Chinese immigrants reported some favourable changes in their dietary intake and greater awareness and more knowledge about healthy foods after immigration. However, an increase in portion size, an increased frequency of dining out and an increased consumption of convenience foods could indicate some unfavourable changes. These results suggest that health promotion strategies should build on the observed benefits of improved nutritional knowledge and target areas of portion size and convenience eating.
PMCID: PMC3118129  PMID: 21592378
15.  Asthma in Black African, Black Caribbean and South Asian adolescents in the MRC DASH study: a cross sectional analysis 
BMC Pediatrics  2010;10:18.
Ethnic differences in the prevalence of asthma among children in the UK are under-researched. We aimed to determine the ethnic differences in the prevalence of asthma and atopic asthma in children from the main UK ethnic groups, and whether differences are associated with differential distributions in social and psychosocial risk factors.
6,643 pupils aged 11-13 years, 80% ethnic minorities. Outcomes were asthma/wheeze with (atopic) and without hay fever/eczema. Risk factors examined were family history of asthma, length of residence in the UK, socioeconomic disadvantage, tobacco exposure, psychological well-being, and body mass index (BMI).
There was a pattern of lower prevalence of asthma in Black African boys and girls, and Indian and Bangladeshi girls compared to White UK. The overall prevalence was higher in Mixed Black Caribbean/White boys, with more atopic asthma in Black Caribbean boys and Mixed Black Caribbean/White boys due to more hayfever. Poor psychological well-being and family history of asthma were associated with an increased risk of asthma within each ethnic group. UK residence for ≤ 5 years was protective for Black Caribbeans and Black Africans. Increased BMI was associated with an increased reporting of asthma for Black Africans. Adjustments for all variables did not remove the excess asthma reported by Black Caribbean boys (atopic) or Mixed Black Caribbean/White boys.
The protective effect of being born abroad accounted for ethnic differences in some groups, signalling a role for socio-environmental factors in patterning ethnic differences in asthma in adolescence.
PMCID: PMC2851680  PMID: 20334698
16.  Evaluation of a Hepatitis B Educational ESL Curriculum for Chinese Immigrants 
According to recent census data, 1,216,600 Canadians are of Chinese descent, and over 80% of Chinese Canadians are foreign born. Approximately 10% of Chinese immigrants are chronic carriers of hepatitis B, compared with less than 0.5% of the general population. English as a second language (ESL) classes provide ready access for individuals with limited English proficiency who are not reached by English language health education materials and media campaigns. We conducted a group-randomized trial to evaluate the effectiveness of a hepatitis B ESL educational curriculum for Chinese immigrants.
Five community-based organizations that provide ESL education in the greater Vancouver area participated in the study. Forty-one ESL classes (which included 325 Chinese students) were randomly assigned to experimental or control status. A follow-up survey, conducted six months after randomization, assessed knowledge about hepatitis B. Generalized estimating equations were used to analyze the data.
Follow-up surveys were completed by 298 (92%) of the students. At follow-up, experimental group students were significantly (p<0.05) more likely than control group students to know that immigrants have higher hepatitis B infection rates than people who were born in Canada; hepatitis B can be spread during childbirth, during sexual intercourse and by sharing razors; hepatitis B is not spread by sharing eating utensils; and hepatitis B infection can cause cirrhosis and liver cancer.
Our findings indicate that ESL curricula can have a positive impact on health knowledge among Chinese immigrants with limited English. Future research should evaluate the effectiveness of ESL curricula for other immigrant groups, as well as other health topics.
PMCID: PMC2836807  PMID: 20209742
Chinese; health education; hepatitis B
17.  Prevalence of asthma and risk factors for asthma-like symptoms in Aboriginal and non-Aboriginal children in the northern territories of Canada 
Few studies have investigated the prevalence and risk factors of asthma in Canadian Aboriginal children.
To determine the prevalence of asthma and asthma-like symptoms, as well as the risk factors for asthma-like symptoms, in Aboriginal and non-Aboriginal children living in the northern territories of Canada.
Data on 2404 children, aged between 0 and 11 years, who participated in the North component of the National Longitudinal Survey of Children and Youth were used in the present study. A child was considered to have an asthma-like symptom if there was a report of ever having had asthma, asthma attacks or wheeze in the past 12 months.
After excluding 59 children with missing information about race, 1399 children (59.7%) were of Aboriginal ancestry. The prevalence of asthma was significantly lower (P<0.05) in Aboriginal children (5.7%) than non-Aboriginal children (10.0%), while the prevalence of wheeze was similar between Aboriginal (15.0%) and non-Aboriginal (14.5%) children. In Aboriginal children, infants and toddlers had a significantly greater prevalence of asthma-like symptoms (30.0%) than preschool-aged children (21.5%) and school-aged children (11.5%). Childhood allergy and a mother’s daily smoking habit were significant risk factors for asthma-like symptoms in both Aboriginal and non-Aboriginal children. In addition, infants and toddlers were at increased risk of asthma-like symptoms in Aboriginal children. In analyses restricted to specific outcomes, a mother’s daily smoking habit was a significant risk factor for current wheeze in Aboriginal children and for ever having had asthma in non-Aboriginal children.
Asthma prevalence appears to be lower in Aboriginal children than in non-Aboriginal children. The association between daily maternal smoking and asthma-like symptoms, which has been mainly reported for children living in urban areas, was observed in Aboriginal and non-Aboriginal children living in northern and remote communities in Canada.
PMCID: PMC2677938  PMID: 18437256
Aboriginals; Asthma; Children; Remote area; Risk factors; Smoking
18.  Lack of awareness of heart disease and stroke among Chinese Canadians: Results of a pilot study of the Chinese Canadian Cardiovascular Health Project 
According to Statistics Canada’s 2001 census, the Chinese make up the largest (27.5%) visible minority population in Canada. The cardiovascular health information for this population is therefore important for the allocation of health care and promotion resources.
In the present pilot study, the authors sought to define the degree of awareness and knowledge of cardiovascular disease, as well as their risk factors, among the Chinese Canadian population.
A 16-item telephone survey was conducted among 1004 ethnic Chinese subjects (18 years of age and older) in the greater Toronto area of Ontario (n=503) and the greater Vancouver area of British Columbia (n=501) in February 2004.
Among the respondents, 73% spoke Cantonese at home and 21% spoke Mandarin. Ninety-seven per cent were immigrants, and 53% had been in Canada for less than 10 years. A history of hypertension was reported in 9.2% of respondents, diabetes in 3.2% and high cholesterol in 14.5%. Thirty-two per cent and 40% of respondents were unable to name at least one symptom of heart attack or stroke, respectively, unaided. Thirty-two per cent and 35% of respondents named at least one incorrect symptom of heart attack and stroke, respectively. When asked about their immediate response in a hypothetical case of a heart attack or stroke, only 20% would have called 911.
The present study is the first to address the awareness of cardiovascular health and disease among Chinese Canadians. These data suggest that Chinese Canadians have a relatively low awareness of the warning symptoms for common cardiovascular emergency situations. The findings presented here have important implications for the development of future health promotion and research initiatives targeted to visible minority populations in Canada.
PMCID: PMC2644359  PMID: 18685742
Chinese; Ethnicity; Myocardial infarction; Population health; Stroke
19.  Chinese and white Canadian satisfaction and compliance with physicians 
BMC Family Practice  2007;8:11.
Patient satisfaction has become an important indicator of primary care and healthcare system performance. Ethnic disparities in patient satisfaction and compliance with physician care have been studied in several countries. However, this issue has not received significant attention in Canada. The unique characteristics of the Canadian healthcare system and ethnic population make it worthwhile to examine this issue in this population. Therefore, we conducted a survey among Chinese and Whites in a Canadian city to determine their reported satisfaction, and perceptions of physicians.
The survey was conducted in English, Mandarin and Cantonese in 2005 among Chinese and White Canadians, 18 years of age or older, who had visited at least one physician in Canada.
We analyzed 746 Chinese and 711 Whites in the general practitioner (GP) visit group and 485 Chinese and 637 Whites in the specialist visit group. A lower proportion of Chinese compared to Whites reported that they were very satisfied or satisfied with GP (73.7% vs. 92.8%) and specialist care (75.5% vs. 85.6%) and the differences between the two groups remained after adjustment for demographic variables and chronic conditions (risk adjusted OR: 0.70, 95%CI: 0.42–1.18 for the GP visit group and OR: 0.77, 95%CI: 0.48–1.23 for the specialist visit group). A similar proportion of Chinese and Whites reported that they always followed a physician's advice (59.4% vs. 59.6% for the GP visit group and 67.2% vs. 62.8% for the specialist visit group). Non-English speaking Chinese and recent arrivals in Canada were less likely to be satisfied with GPs than Chinese born in Canada [risk adjusted OR: 0.5, 95%CI: 0.3–0.9, 0.2 and 0.1–0.7, respectively].
Chinese Canadians reported lower satisfaction with physicians and perceived physicians slightly more negatively than White Canadians. Particularly, Chinese with limited English and short length of stay in Canada were less satisfied than Canadian born Chinese.
PMCID: PMC1847678  PMID: 17376235
20.  Bicycle helmet use and bicycling-related injury among young Canadians: an equity analysis 
Cycling is a major activity for adolescents in Canada and potential differences exist in bicycling-related risk and experience of injury by population subgroup. The overall aim of this study was to inform health equity interventions by profiling stratified analytic methods and identifying potential inequities associated with bicycle-related injury and the use of bicycle helmets among Canadian youth. The two objectives of this study were: (1) To examine national patterns in bicycle ridership and also bicycle helmet use among Canadian youth in a stratified analysis by potentially vulnerable population subgroups, and (2) To examine bicycling-related injury in the same population subgroups of Canadian youth in order to identify possible health inequities.
Data for this study were obtained from the 6th cycle (2009/10) of the Health Behaviour in School-aged Children (HBSC) study, which is a general health survey that was completed by 26,078 students in grades 6–10 from 436 Canadian schools. Based on survey responses, we determined point prevalence for bicycle ridership, bicycle helmet use and relative risks for bicycling-related injury.
Three quarters of all respondents were bicycle riders (n=19,410). Independent factors associated with bicycle ridership among students include being male, being a younger student, being more affluent, and being a resident of a small town. Among bicycle riders, 43% (95%CI ± 0.6%) reported never wearing and 32% (± 0.6%) inconsistently wearing a helmet. Only 26% (± 0.5%) of students reported always wearing a bicycle helmet. Helmets were less frequently used among older students and there were also important patterns by sex, geographic location and socioeconomic status. Adjusting for all other demographic characteristics, boys reported 2.02-fold increase (95% CI: 1.61 to 1.90) and new immigrants a 1.35-fold increase (95%CI: 1.00 to1.82) in the relative risk of bicycling-related injury in the past 12 months, as compared to girls and students born in Canada. The relative risk of injury did not vary significantly by levels of socioeconomic status.
Troubling disparities exist in bicycle use, bicycle helmet use and bicycling-related injuries across specific population subgroups. Bicycle safety and injury prevention initiatives should be informed by disaggregated analyses and the context of bicycle-related health differences should be further examined.
PMCID: PMC3702522  PMID: 23819527
21.  The prevalence of childhood asthma in China: a systematic review 
BMC Public Health  2012;12:860.
It is well known that the prevalence of asthma has been reported to increase in many places around the world during the last decades. Therefore, the aim of this study was to identify and review studies of asthma prevalence among children in China and address time trends and regional variation in asthma.
A systematic literature search was performed using PubMed and China National Knowledge Infrastructure (CNKI) databases. Selected articles had to describe an original study that showed the prevalence of asthma among children aged 0−14 years.
A total of 74 articles met the inclusion criteria. The lifetime prevalence of asthma varied between 1.1% in Lhasa (Tibet) and 11.0% in Hong Kong in studies following the International Study of Asthma and Allergies in Childhood (ISAAC) protocol. The prevalence was 3% or lower in most articles following Chinese diagnostic criteria. One article reported the results from two national surveys and showed that the current average prevalence of asthma for the total study population had increased from 1990 to 2000 (0.9% to 1.5%). The lowest current prevalence was found in Lhasa (0.1% in 1990, 0.5% in 2000).
The prevalence of childhood asthma was generally low, both in studies following the ISAAC and Chinese diagnostic criteria. Assessment of time trends and regional variations in asthma prevalence was difficult due to insufficient data, variation in diagnostic criteria, difference in data collection methods, and uncertainty in prevalence measures. However, the findings from one large study of children from 27 different cities support an increase in current prevalence of childhood asthma from 1990 to 2000. The lowest current prevalence of childhood asthma was found in Tibet.
PMCID: PMC3524042  PMID: 23050953
Asthma; Children; Prevalence; Altitude; Systematic review
22.  Clinical Utility of Vitamin D Testing 
Executive Summary
This report from the Medical Advisory Secretariat (MAS) was intended to evaluate the clinical utility of vitamin D testing in average risk Canadians and in those with kidney disease. As a separate analysis, this report also includes a systematic literature review of the prevalence of vitamin D deficiency in these two subgroups.
This evaluation did not set out to determine the serum vitamin D thresholds that might apply to non-bone health outcomes. For bone health outcomes, no high or moderate quality evidence could be found to support a target serum level above 50 nmol/L. Similarly, no high or moderate quality evidence could be found to support vitamin D’s effects in non-bone health outcomes, other than falls.
Vitamin D
Vitamin D is a lipid soluble vitamin that acts as a hormone. It stimulates intestinal calcium absorption and is important in maintaining adequate phosphate levels for bone mineralization, bone growth, and remodelling. It’s also believed to be involved in the regulation of cell growth proliferation and apoptosis (programmed cell death), as well as modulation of the immune system and other functions. Alone or in combination with calcium, Vitamin D has also been shown to reduce the risk of fractures in elderly men (≥ 65 years), postmenopausal women, and the risk of falls in community-dwelling seniors. However, in a comprehensive systematic review, inconsistent results were found concerning the effects of vitamin D in conditions such as cancer, all-cause mortality, and cardiovascular disease. In fact, no high or moderate quality evidence could be found concerning the effects of vitamin D in such non-bone health outcomes. Given the uncertainties surrounding the effects of vitamin D in non-bone health related outcomes, it was decided that this evaluation should focus on falls and the effects of vitamin D in bone health and exclusively within average-risk individuals and patients with kidney disease.
Synthesis of vitamin D occurs naturally in the skin through exposure to ultraviolet B (UVB) radiation from sunlight, but it can also be obtained from dietary sources including fortified foods, and supplements. Foods rich in vitamin D include fatty fish, egg yolks, fish liver oil, and some types of mushrooms. Since it is usually difficult to obtain sufficient vitamin D from non-fortified foods, either due to low content or infrequent use, most vitamin D is obtained from fortified foods, exposure to sunlight, and supplements.
Clinical Need: Condition and Target Population
Vitamin D deficiency may lead to rickets in infants and osteomalacia in adults. Factors believed to be associated with vitamin D deficiency include:
darker skin pigmentation,
winter season,
living at higher latitudes,
skin coverage,
kidney disease,
malabsorption syndromes such as Crohn’s disease, cystic fibrosis, and
genetic factors.
Patients with chronic kidney disease (CKD) are at a higher risk of vitamin D deficiency due to either renal losses or decreased synthesis of 1,25-dihydroxyvitamin D.
Health Canada currently recommends that, until the daily recommended intakes (DRI) for vitamin D are updated, Canada’s Food Guide (Eating Well with Canada’s Food Guide) should be followed with respect to vitamin D intake. Issued in 2007, the Guide recommends that Canadians consume two cups (500 ml) of fortified milk or fortified soy beverages daily in order to obtain a daily intake of 200 IU. In addition, men and women over the age of 50 should take 400 IU of vitamin D supplements daily. Additional recommendations were made for breastfed infants.
A Canadian survey evaluated the median vitamin D intake derived from diet alone (excluding supplements) among 35,000 Canadians, 10,900 of which were from Ontario. Among Ontarian males ages 9 and up, the median daily dietary vitamin D intake ranged between 196 IU and 272 IU per day. Among females, it varied from 152 IU to 196 IU per day. In boys and girls ages 1 to 3, the median daily dietary vitamin D intake was 248 IU, while among those 4 to 8 years it was 224 IU.
Vitamin D Testing
Two laboratory tests for vitamin D are available, 25-hydroxy vitamin D, referred to as 25(OH)D, and 1,25-dihydroxyvitamin D. Vitamin D status is assessed by measuring the serum 25(OH)D levels, which can be assayed using radioimmunoassays, competitive protein-binding assays (CPBA), high pressure liquid chromatography (HPLC), and liquid chromatography-tandem mass spectrometry (LC-MS/MS). These may yield different results with inter-assay variation reaching up to 25% (at lower serum levels) and intra-assay variation reaching 10%.
The optimal serum concentration of vitamin D has not been established and it may change across different stages of life. Similarly, there is currently no consensus on target serum vitamin D levels. There does, however, appear to be a consensus on the definition of vitamin D deficiency at 25(OH)D < 25 nmol/l, which is based on the risk of diseases such as rickets and osteomalacia. Higher target serum levels have also been proposed based on subclinical endpoints such as parathyroid hormone (PTH). Therefore, in this report, two conservative target serum levels have been adopted, 25 nmol/L (based on the risk of rickets and osteomalacia), and 40 to 50 nmol/L (based on vitamin D’s interaction with PTH).
Ontario Context
Volume & Cost
The volume of vitamin D tests done in Ontario has been increasing over the past 5 years with a steep increase of 169,000 tests in 2007 to more than 393,400 tests in 2008. The number of tests continues to rise with the projected number of tests for 2009 exceeding 731,000. According to the Ontario Schedule of Benefits, the billing cost of each test is $51.7 for 25(OH)D (L606, 100 LMS units, $0.517/unit) and $77.6 for 1,25-dihydroxyvitamin D (L605, 150 LMS units, $0.517/unit). Province wide, the total annual cost of vitamin D testing has increased from approximately $1.7M in 2004 to over $21.0M in 2008. The projected annual cost for 2009 is approximately $38.8M.
Evidence-Based Analysis
The objective of this report is to evaluate the clinical utility of vitamin D testing in the average risk population and in those with kidney disease. As a separate analysis, the report also sought to evaluate the prevalence of vitamin D deficiency in Canada. The specific research questions addressed were thus:
What is the clinical utility of vitamin D testing in the average risk population and in subjects with kidney disease?
What is the prevalence of vitamin D deficiency in the average risk population in Canada?
What is the prevalence of vitamin D deficiency in patients with kidney disease in Canada?
Clinical utility was defined as the ability to improve bone health outcomes with the focus on the average risk population (excluding those with osteoporosis) and patients with kidney disease.
Literature Search
A literature search was performed on July 17th, 2009 using OVID MEDLINE, MEDLINE In-Process and Other Non-Indexed Citations, EMBASE, the Cumulative Index to Nursing & Allied Health Literature (CINAHL), the Cochrane Library, and the International Agency for Health Technology Assessment (INAHTA) for studies published from January 1, 1998 until July 17th, 2009. Abstracts were reviewed by a single reviewer and, for those studies meeting the eligibility criteria, full-text articles were obtained. Reference lists were also examined for any additional relevant studies not identified through the search. Articles with unknown eligibility were reviewed with a second clinical epidemiologist, then a group of epidemiologists until consensus was established. The quality of evidence was assessed as high, moderate, low or very low according to GRADE methodology.
Observational studies that evaluated the prevalence of vitamin D deficiency in Canada in the population of interest were included based on the inclusion and exclusion criteria listed below. The baseline values were used in this report in the case of interventional studies that evaluated the effect of vitamin D intake on serum levels. Studies published in grey literature were included if no studies published in the peer-reviewed literature were identified for specific outcomes or subgroups.
Considering that vitamin D status may be affected by factors such as latitude, sun exposure, food fortification, among others, the search focused on prevalence studies published in Canada. In cases where no Canadian prevalence studies were identified, the decision was made to include studies from the United States, given the similar policies in vitamin D food fortification and recommended daily intake.
Inclusion Criteria
Studies published in English
Publications that reported the prevalence of vitamin D deficiency in Canada
Studies that included subjects from the general population or with kidney disease
Studies in children or adults
Studies published between January 1998 and July 17th 2009
Exclusion Criteria
Studies that included subjects defined according to a specific disease other than kidney disease
Letters, comments, and editorials
Studies that measured the serum vitamin D levels but did not report the percentage of subjects with serum levels below a given threshold
Outcomes of Interest
Prevalence of serum vitamin D less than 25 nmol/L
Prevalence of serum vitamin D less than 40 to 50 nmol/L
Serum 25-hydroxyvitamin D was the metabolite used to assess vitamin D status. Results from adult and children studies were reported separately. Subgroup analyses according to factors that affect serum vitamin D levels (e.g., seasonal effects, skin pigmentation, and vitamin D intake) were reported if enough information was provided in the studies
Quality of Evidence
The quality of the prevalence studies was based on the method of subject recruitment and sampling, possibility of selection bias, and generalizability to the source population. The overall quality of the trials was examined according to the GRADE Working Group criteria.
Summary of Findings
Fourteen prevalence studies examining Canadian adults and children met the eligibility criteria. With the exception of one longitudinal study, the studies had a cross-sectional design. Two studies were conducted among Canadian adults with renal disease but none studied Canadian children with renal disease (though three such US studies were included). No systematic reviews or health technology assessments that evaluated the prevalence of vitamin D deficiency in Canada were identified. Two studies were published in grey literature, consisting of a Canadian survey designed to measure serum vitamin D levels and a study in infants presented as an abstract at a conference. Also included were the results of vitamin D tests performed in community laboratories in Ontario between October 2008 and September 2009 (provided by the Ontario Association of Medical Laboratories).
Different threshold levels were used in the studies, thus we reported the percentage of subjects with serum levels of between 25 and 30 nmol/L and between 37.5 and 50 nmol/L. Some studies stratified the results according to factors affecting vitamin D status and two used multivariate models to investigate the effects of these characteristics (including age, season, BMI, vitamin D intake, skin pigmentation, and season) on serum 25(OH)D levels. It’s unclear, however, if these studies were adequately powered for these subgroup analyses.
Study participants generally consisted of healthy, community-dwelling subjects and most excluded individuals with conditions or medications that alter vitamin D or bone metabolism, such as kidney or liver disease. Although the studies were conducted in different parts of Canada, fewer were performed in Northern latitudes, i.e. above 53°N, which is equivalent to the city of Edmonton.
Serum vitamin D levels of < 25 to 30 nmol/L were observed in 0% to 25.5% of the subjects included in five studies; the weighted average was 3.8% (95% CI: 3.0, 4.6). The preliminary results of the Canadian survey showed that approximately 5% of the subjects had serum levels below 29.5 nmol/L. The results of over 600,000 vitamin D tests performed in Ontarian community laboratories between October 2008 and September 2009 showed that 2.6% of adults (> 18 years) had serum levels < 25 nmol/L.
The prevalence of serum vitamin D levels below 37.5-50 nmol/L reported among studies varied widely, ranging from 8% to 73.6% with a weighted average of 22.5%. The preliminary results of the CHMS survey showed that between 10% and 25% of subjects had serum levels below 37 to 48 nmol/L. The results of the vitamin D tests performed in community laboratories showed that 10% to 25% of the individuals had serum levels between 39 and 50 nmol/L.
In an attempt to explain this inter-study variation, the study results were stratified according to factors affecting serum vitamin D levels, as summarized below. These results should be interpreted with caution as none were adjusted for other potential confounders. Adequately powered multivariate analyses would be necessary to determine the contribution of risk factors to lower serum 25(OH)D levels.
Seasonal variation
Three adult studies evaluating serum vitamin D levels in different seasons observed a trend towards a higher prevalence of serum levels < 37.5 to 50 nmol/L during the winter and spring months, specifically 21% to 39%, compared to 8% to 14% in the summer. The weighted average was 23.6% over the winter/spring months and 9.6% over summer. The difference between the seasons was not statistically significant in one study and not reported in the other two studies.
Skin Pigmentation
Four studies observed a trend toward a higher prevalence of serum vitamin D levels < 37.5 to 50 nmol/L in subjects with darker skin pigmentation compared to those with lighter skin pigmentation, with weighted averages of 46.8% among adults with darker skin colour and 15.9% among those with fairer skin.
Vitamin D intake and serum levels
Four adult studies evaluated serum vitamin D levels according to vitamin D intake and showed an overall trend toward a lower prevalence of serum levels < 37.5 to 50 nmol/L with higher levels of vitamin D intake. One study observed a dose-response relationship between higher vitamin D intake from supplements, diet (milk), and sun exposure (results not adjusted for other variables). It was observed that subjects taking 50 to 400 IU or > 400 IU of vitamin D per day had a 6% and 3% prevalence of serum vitamin D level < 40 nmol/L, respectively, versus 29% in subjects not on vitamin D supplementation. Similarly, among subjects drinking one or two glasses of milk per day, the prevalence of serum vitamin D levels < 40 nmol/L was found to be 15%, versus 6% in those who drink more than two glasses of milk per day and 21% among those who do not drink milk. On the other hand, one study observed little variation in serum vitamin D levels during winter according to milk intake, with the proportion of subjects exhibiting vitamin D levels of < 40 nmol/L being 21% among those drinking 0-2 glasses per day, 26% among those drinking > 2 glasses, and 20% among non-milk drinkers.
The overall quality of evidence for the studies conducted among adults was deemed to be low, although it was considered moderate for the subgroups of skin pigmentation and seasonal variation.
Newborn, Children and Adolescents
Five Canadian studies evaluated serum vitamin D levels in newborns, children, and adolescents. In four of these, it was found that between 0 and 36% of children exhibited deficiency across age groups with a weighted average of 6.4%. The results of over 28,000 vitamin D tests performed in children 0 to 18 years old in Ontario laboratories (Oct. 2008 to Sept. 2009) showed that 4.4% had serum levels of < 25 nmol/L.
According to two studies, 32% of infants 24 to 30 months old and 35.3% of newborns had serum vitamin D levels of < 50 nmol/L. Two studies of children 2 to 16 years old reported that 24.5% and 34% had serum vitamin D levels below 37.5 to 40 nmol/L. In both studies, older children exhibited a higher prevalence than younger children, with weighted averages 34.4% and 10.3%, respectively. The overall weighted average of the prevalence of serum vitamin D levels < 37.5 to 50 nmol/L among pediatric studies was 25.8%. The preliminary results of the Canadian survey showed that between 10% and 25% of subjects between 6 and 11 years (N= 435) had serum levels below 50 nmol/L, while for those 12 to 19 years, 25% to 50% exhibited serum vitamin D levels below 50 nmol/L.
The effects of season, skin pigmentation, and vitamin D intake were not explored in Canadian pediatric studies. A Canadian surveillance study did, however, report 104 confirmed cases1 (2.9 cases per 100,000 children) of vitamin D-deficient rickets among Canadian children age 1 to 18 between 2002 and 2004, 57 (55%) of which from Ontario. The highest incidence occurred among children living in the North, i.e., the Yukon, Northwest Territories, and Nunavut. In 92 (89%) cases, skin pigmentation was categorized as intermediate to dark, 98 (94%) had been breastfed, and 25 (24%) were offspring of immigrants to Canada. There were no cases of rickets in children receiving ≥ 400 IU VD supplementation/day.
Overall, the quality of evidence of the studies of children was considered very low.
Kidney Disease
Two studies evaluated serum vitamin D levels in Canadian adults with kidney disease. The first included 128 patients with chronic kidney disease stages 3 to 5, 38% of which had serum vitamin D levels of < 37.5 nmol/L (measured between April and July). This is higher than what was reported in Canadian studies of the general population during the summer months (i.e. between 8% and 14%). In the second, which examined 419 subjects who had received a renal transplantation (mean time since transplantation: 7.2 ± 6.4 years), the prevalence of serum vitamin D levels < 40 nmol/L was 27.3%. The authors concluded that the prevalence observed in the study population was similar to what is expected in the general population.
No studies evaluating serum vitamin D levels in Canadian pediatric patients with kidney disease could be identified, although three such US studies among children with chronic kidney disease stages 1 to 5 were. The mean age varied between 10.7 and 12.5 years in two studies but was not reported in the third. Across all three studies, the prevalence of serum vitamin D levels below the range of 37.5 to 50 nmol/L varied between 21% and 39%, which is not considerably different from what was observed in studies of healthy Canadian children (24% to 35%).
Overall, the quality of evidence in adults and children with kidney disease was considered very low.
Clinical Utility of Vitamin D Testing
A high quality comprehensive systematic review published in August 2007 evaluated the association between serum vitamin D levels and different bone health outcomes in different age groups. A total of 72 studies were included. The authors observed that there was a trend towards improvement in some bone health outcomes with higher serum vitamin D levels. Nevertheless, precise thresholds for improved bone health outcomes could not be defined across age groups. Further, no new studies on the association were identified during an updated systematic review on vitamin D published in July 2009.
With regards to non-bone health outcomes, there is no high or even moderate quality evidence that supports the effectiveness of vitamin D in outcomes such as cancer, cardiovascular outcomes, and all-cause mortality. Even if there is any residual uncertainty, there is no evidence that testing vitamin D levels encourages adherence to Health Canada’s guidelines for vitamin D intake. A normal serum vitamin D threshold required to prevent non-bone health related conditions cannot be resolved until a causal effect or correlation has been demonstrated between vitamin D levels and these conditions. This is as an ongoing research issue around which there is currently too much uncertainty to base any conclusions that would support routine vitamin D testing.
For patients with chronic kidney disease (CKD), there is again no high or moderate quality evidence supporting improved outcomes through the use of calcitriol or vitamin D analogs. In the absence of such data, the authors of the guidelines for CKD patients consider it best practice to maintain serum calcium and phosphate at normal levels, while supplementation with active vitamin D should be considered if serum PTH levels are elevated. As previously stated, the authors of guidelines for CKD patients believe that there is not enough evidence to support routine vitamin D [25(OH)D] testing. According to what is stated in the guidelines, decisions regarding the commencement or discontinuation of treatment with calcitriol or vitamin D analogs should be based on serum PTH, calcium, and phosphate levels.
Limitations associated with the evidence of vitamin D testing include ambiguities in the definition of an ‘adequate threshold level’ and both inter- and intra- assay variability. The MAS considers both the lack of a consensus on the target serum vitamin D levels and assay limitations directly affect and undermine the clinical utility of testing. The evidence supporting the clinical utility of vitamin D testing is thus considered to be of very low quality.
Daily vitamin D intake, either through diet or supplementation, should follow Health Canada’s recommendations for healthy individuals of different age groups. For those with medical conditions such as renal disease, liver disease, and malabsorption syndromes, and for those taking medications that may affect vitamin D absorption/metabolism, physician guidance should be followed with respect to both vitamin D testing and supplementation.
Studies indicate that vitamin D, alone or in combination with calcium, may decrease the risk of fractures and falls among older adults.
There is no high or moderate quality evidence to support the effectiveness of vitamin D in other outcomes such as cancer, cardiovascular outcomes, and all-cause mortality.
Studies suggest that the prevalence of vitamin D deficiency in Canadian adults and children is relatively low (approximately 5%), and between 10% and 25% have serum levels below 40 to 50 nmol/L (based on very low to low grade evidence).
Given the limitations associated with serum vitamin D measurement, ambiguities in the definition of a ‘target serum level’, and the availability of clear guidelines on vitamin D supplementation from Health Canada, vitamin D testing is not warranted for the average risk population.
Health Canada has issued recommendations regarding the adequate daily intake of vitamin D, but current studies suggest that the mean dietary intake is below these recommendations. Accordingly, Health Canada’s guidelines and recommendations should be promoted.
Based on a moderate level of evidence, individuals with darker skin pigmentation appear to have a higher risk of low serum vitamin D levels than those with lighter skin pigmentation and therefore may need to be specially targeted with respect to optimum vitamin D intake. The cause-effect of this association is currently unclear.
Individuals with medical conditions such as renal and liver disease, osteoporosis, and malabsorption syndromes, as well as those taking medications that may affect vitamin D absorption/metabolism, should follow their physician’s guidance concerning both vitamin D testing and supplementation.
PMCID: PMC3377517  PMID: 23074397
23.  Risk factors for breast cancer in postmenopausal Caucasian and Chinese-Canadian women 
Striking differences exist between countries in the incidence of breast cancer. The causes of these differences are unknown, but because incidence rates change in migrants, they are thought to be due to lifestyle rather than genetic differences. The goal of this cross-sectional study was to examine breast cancer risk factors in populations with different risks for breast cancer.
We compared breast cancer risk factors among three groups of postmenopausal Canadian women at substantially different risk of developing breast cancer - Caucasians (N = 413), Chinese women born in the West or who migrated to the West before age 21 (N = 216), and recent Chinese migrants (N = 421). Information on risk factors and dietary acculturation were collected by telephone interviews using questionnaires, and anthropometric measurements were taken at a home visit.
Compared to Caucasians, recent Chinese migrants weighed on average 14 kg less, were 6 cm shorter, had menarche a year later, were more often parous, less often had a family history of breast cancer or a benign breast biopsy, a higher Chinese dietary score, and a lower Western dietary score. For most of these variables, Western born Chinese and early Chinese migrants had values intermediate between those of Caucasians and recent Chinese migrants. We estimated five-year absolute risks for breast cancer using the Gail Model and found that risk estimates in Caucasians would be reduced by only 11% if they had the risk factor profile of recent Chinese migrants for the risk factors in the Gail Model.
Our results suggest that in addition to the risk factors in the Gail Model, there likely are other factors that also contribute to the large difference in breast cancer risk between Canada and China.
PMCID: PMC2880420  PMID: 20053286
24.  Dramatic Increases in Obesity and Overweight Prevalence among Asian Subgroups in the United States, 1992–2011 
ISRN Preventive Medicine  2013;2013:898691.
We examined trends in adult obesity and overweight prevalence among major Asian/Pacific Islander (API) subgroups and the non-Hispanic whites from 1992 to 2011. Using 1992–2011 National Health Interview Surveys, obesity, overweight, and BMI differentials were analyzed by logistic, linear, and log-linear regression. Between 1992 and 2011, obesity prevalence doubled for the Chinese, the Asian Indians, the Japanese, and the Hawaiians/Pacific Islanders; and tripled for the Filipinos. Obesity prevalence among API adults tripled from 3.7% in 1992 to 13.3% in 2010, and overweight prevalence doubled from 23.2% to 43.1%. Immigrants in each API subgroup had lower prevalence than their US-born counterparts, with immigrants' obesity and overweight risks increasing with increasing duration of residence. During 2006–2011, obesity prevalence ranged from 3.3% for Chinese immigrants to 22.3% for the US-born Filipinos and 41.1% for the Native Hawaiians/Pacific Islanders. The Asian Indians, the Filipinos, and the Hawaiians/Pacific Islanders had, respectively, 3.1, 3.8, and 10.9 times higher odds of obesity than those of the Chinese adults. Compared with Chinese immigrants, the adjusted odds of obesity were 3.5–4.6 times higher for the US-born Chinese and the foreign-born Filipinos, 9 times higher for the US-born Filipinos and whites, 3.8–5.5 times higher for the US-born and foreign-born Asian Indians, and 21.9 times higher for the Native Hawaiians. Substantial ethnic heterogeneity and rising prevalence underscore the need for increased monitoring of obesity and obesity-related risk factors among API subgroups.
PMCID: PMC4045452  PMID: 24967142
25.  The childbearing health and related service needs of newcomers (CHARSNN) study protocol 
Refugee and asylum-seeking women in Canada may have significant harmful childbearing health outcomes and unmet health and social care needs. The most vulnerable of these women are: those who have left their countries by force (e.g., war, rape or abuse histories), are separated from their families, have limited knowledge of the host country languages, and are visible minorities. Asylum-seekers face additional stresses related to their unknown future status and are marginalized with regards to access to provincial health care systems. The prevalence and severity of health issues in this population is not known nor is the extent of response from social service and health care systems (including variation in provincial service delivery). Understanding the magnitude of health and social concerns of newcomers requires data from a representative sample of childbearing refugee and asylum-seeking women resettling in Canada to permit comparisons to be made with non-refugee immigrant and Canadian-born women. Our research questions are: (1) Do refugee or asylum-seeking women and their infants, experience a greater number or a different distribution of harmful health events during pregnancy, at birth, and during the postpartum period than non-refugee immigrant or Canadian-born women? (2) Are the harmful health events experienced postpartum by asylum-seeking women and their infants, addressed less often (compared to refugees, non-refugee immigrants, and Canadian-born women) by the Canadian health care system as delivered in each of the three major receiving cities for newcomers?
This is a four-year multi-site prospective cohort study (pregnancy to 4 months postpartum). We will seek to recruit 2400 women [200 in each of 4 groups (refugees, asylum-seekers, non-refugee immigrants, and Canadian-born) from 1 of 12 postpartum hospital units across the 3 largest receiving cities for newcomers to Canada – Montreal, Toronto, and Vancouver].
Knowledge of the extent of harmful health events occurring to asylum-seeking, refugee, immigrant, and Canadian-born women, and the response of the health care system to those events and group differences, if they exist, will inform immigration and health policy makers as well as providers of services.
PMCID: PMC1797193  PMID: 17190589

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