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1.  Blood Drain: Soil-Transmitted Helminths and Anemia in Pregnant Women 
PMCID: PMC4091787  PMID: 25010736
2.  Temporal trends in sudden infant death syndrome in Canada from 1991 to 2005: contribution of changes in cause of death assignment practices and in maternal and infant characteristics 
Gilbert NL, Fell DB, Joseph KS, Liu S, León JA, Sauve R, for the Fetal and Infant Health Study Group of the Canadian Perinatal Surveillance System. Temporal trends in sudden infant death syndrome in Canada from 1991 to 2005: contribution of changes in cause of death assignment practices and in maternal and infant characteristics. Paediatric and Perinatal Epidemiology 2012; 26: 124–130.
The rate of sudden infant death syndrome (SIDS) declined significantly in Canada and the US between the late 1980s and the early 2000s. In the US, this decline was shown to be due in part to a shift in diagnosis, as deaths from accidental suffocation and strangulation in bed and from other ill-defined and unspecified cause increased concurrently. This study was undertaken to determine whether there was such a shift in diagnosis from SIDS to other causes of death in Canada, and to quantify the true temporal decrease in SIDS. Cause-specific infant death rates were compared across three periods: 1991–95, 1996–2000 and 2001–05 using the Canadian linked livebirth-infant death file. The temporal decline in SIDS was estimated after adjustment for maternal and infant characteristics such as maternal age and small-for-gestational age using logistic regression. Deaths from SIDS decreased from 78.4 [95% confidence interval (CI) 73.4, 83.4] per 100 000 livebirths in 1991–95, to 48.5 [95% CI 44.3, 52.7] in 1996–2000 and to 34.6 [95% CI 31.0, 38.3] in 2001–05. Mortality rates from other ill-defined and unspecified causes and accidental suffocation and strangulation in bed remained stable. The temporal decline in SIDS between 1991–95 and 2001–05 did not change substantially after adjustment for maternal and infant factors. It is unlikely that the temporal decline of SIDS in Canada was due to changes in cause-of-death assignment practices or in maternal and infant characteristics.
PMCID: PMC3321219  PMID: 22324498
SIDS; time trend; Canada
3.  Re-Visiting Trichuris trichiura Intensity Thresholds Based on Anemia during Pregnancy 
The intensity categories, or thresholds, currently used for Trichuris trichiura (ie. epg intensities of 1–999 (light); 1,000–9,999 epg (moderate), and ≥10,000 epg (heavy)) were developed in the 1980s, when there were little epidemiological data available on dose-response relationships. This study was undertaken to determine a threshold for T. trichiura-associated anemia in pregnant women and to describe the implications of this threshold in terms of the need for primary prevention and chemotherapeutic interventions.
Methodology/Principal Findings
In Iquitos, Peru, 935 pregnant women were tested for T. trichiura infection in their second trimester of pregnancy; were given daily iron supplements throughout their pregnancy; and had their blood hemoglobin levels measured in their third trimester of pregnancy. Women in the highest two T. trichiura intensity quintiles (601–1632 epg and ≥1633 epg) had significantly lower mean hemoglobin concentrations than the lowest quintile (0–24 epg). They also had a statistically significantly higher risk of anemia, with adjusted odds ratios of 1.67 (95% CI: 1.02, 2.62) and 1.73 (95% CI: 1.09, 2.74), respectively.
This analysis provides support for categorizing a T. trichiura infection ≥1,000 epg as ‘moderate’, as currently defined by the World Health Organization. Because this ‘moderate’ level of T. trichiura infection was found to be a significant risk factor for anemia in pregnant women, the intensity of Trichuris infection deemed to cause or aggravate anemia should no longer be restricted to the ‘heavy’ intensity category. It should now include both ‘heavy’ and ‘moderate’ intensities of Trichuris infection. Evidence-based deworming strategies targeting pregnant women or populations where anemia is of concern should be updated accordingly.
Author Summary
Infection by the soil-transmitted helminth Trichuris trichiura is defined as ‘light’, ‘moderate’ and ‘heavy’ depending on its intensity. However, these intensity categories were developed in the 1980s, before any epidemiological data were available on the association between specific T. trichiura infection intensities and adverse health outcomes. Here, we re-analyzed data from a study of T. trichiura infection and anemia in pregnant women to determine the threshold (i.e. the lowest infection intensity) associated with an increased risk of anemia. Women with T. trichiura infections of intensities ranging from 601 to 1632 eggs per gram of feces (epg) (ie. a ‘moderate’ level of intensity) had a significantly higher prevalence of anemia and a significantly lower hemoglobin level than the reference group (i.e. women with T. trichiura infections of intensities ranging between 0 and 24 epg). This finding contrasts with the common belief that only ‘heavy’ T. trichiura infection (10,000 epg and above) can cause anemia.
PMCID: PMC3441397  PMID: 23029572
4.  Asthma and allergic disease prevalence in a diverse sample of Toronto school children: Results from the Toronto Child Health Evaluation Questionnaire (T-CHEQ) Study 
Asthma is the most common chronic disease in children.
To describe the prevalence of asthma and allergic disease in a multiethnic, population-based sample of Toronto (Ontario) school children attending grades 1 and 2.
In 2006, the Toronto Child Health Evaluation Questionnaire (T-CHEQ) used the International Study of Asthma and Allergies in Childhood survey methodology to administer questionnaires to 23,379 Toronto school children attending grades 1 and 2. Modifications were made to the methodology to conform with current privacy legislation and capture the ethnic diversity of the population. Lifetime asthma, wheeze, hay fever and eczema prevalence were defined by parental report. Asthma was considered to be current if the child also reported wheeze or asthma medication use in the previous 12 months.
A total of 5619 children from 283 randomly sampled public schools participated. Children were five to nine years of age, with a mean age of 6.7 years. The overall prevalence of lifetime asthma was 16.1%, while only 11.3% had current asthma. The reported prevalence of lifetime wheeze was 29.2%, while 14.2% reported wheeze in the past 12 months. Sociodemographic and major health determinant characteristics of the T-CHEQ population were similar to 2001 census data, suggesting a diverse sample that was representative of the urban childhood population.
Asthma continues to be a highly prevalent chronic disease in Canadian children. A large proportion of children with reported lifetime asthma, who were five to nine years of age, did not report current asthma symptomatology or medication use.
PMCID: PMC2866206  PMID: 20186360
Childhood asthma; Epidemiology; Survey research
5.  Predictors of Indoor Air Concentrations in Smoking and Non-Smoking Residences 
Indoor concentrations of air pollutants (benzene, toluene, formaldehyde, acetaldehyde, acrolein, nitrogen dioxide, particulate matter, elemental carbon and ozone) were measured in residences in Regina, Saskatchewan, Canada. Data were collected in 106 homes in winter and 111 homes in summer of 2007, with 71 homes participating in both seasons. In addition, data for relative humidity, temperature, air exchange rates, housing characteristics and occupants’ activities during sampling were collected. Multiple linear regression analysis was used to construct season-specific models for the air pollutants. Where smoking was a major contributor to indoor concentrations, separate models were constructed for all homes and for those homes with no cigarette smoke exposure. The housing characteristics and occupants’ activities investigated in this study explained between 11% and 53% of the variability in indoor air pollutant concentrations, with ventilation, age of home and attached garage being important predictors for many pollutants.
PMCID: PMC2954570  PMID: 20948949
residential indoor air quality; exposure; sources
6.  A Cohort Study of Traffic-Related Air Pollution and Mortality in Toronto, Ontario, Canada 
Environmental Health Perspectives  2009;117(5):772-777.
Chronic exposure to traffic-related air pollution (TRAP) may contribute to premature mortality, but few studies to date have addressed this topic.
In this study we assessed the association between TRAP and mortality in Toronto, Ontario, Canada.
We collected nitrogen dioxide samples over two seasons using duplicate two-sided Ogawa passive diffusion samplers at 143 locations across Toronto. We calibrated land use regressions to predict NO2 exposure on a fine scale within Toronto. We used interpolations to predict levels of particulate matter with aerodynamic diameter ≤ 2.5 μm (PM2.5) and ozone levels. We assigned predicted pollution exposures to 2,360 subjects from a respiratory clinic, and abstracted health data on these subjects from medical billings, lung function tests, and diagnoses by pulmonologists. We tracked mortality between 1992 and 2002. We used standard and multilevel Cox proportional hazard models to test associations between air pollution and mortality.
After controlling for age, sex, lung function, obesity, smoking, and neighborhood deprivation, we observed a 17% increase in all-cause mortality and a 40% increase in circulatory mortality from an exposure contrast across the interquartile range of 4 ppb NO2. We observed no significant associations with other pollutants.
Exposure to TRAP was significantly associated with increased all-cause and circulatory mortality in this cohort. A high prevalence of cardiopulmonary disease in the cohort probably limits inference of the findings to populations with a substantial proportion of susceptible individuals.
PMCID: PMC2685840  PMID: 19479020
air pollution; GIS; mortality; nitrogen dioxide; traffic air pollution; Toronto
7.  Quality of indoor residential air and health 
About 90% of our time is spent indoors where we are exposed to chemical and biological contaminants and possibly to carcinogens. These agents may influence the risk of developing nonspecific respiratory and neurologic symptoms, allergies, asthma and lung cancer. We review the sources, health effects and control strategies for several of these agents. There are conflicting data about indoor allergens. Early exposure may increase or may decrease the risk of future sensitization. Reports of indoor moulds or dampness or both are consistently associated with increased respiratory symptoms but causality has not been established. After cigarette smoking, exposure to environmental tobacco smoke and radon are the most common causes of lung cancer. Homeowners can improve the air quality in their homes, often with relatively simple measures, which should provide health benefits.
PMCID: PMC2443227  PMID: 18625986
8.  Indoor air quality and the risk of lower respiratory tract infections in young Canadian Inuit children 
Inuit infants have the highest reported rate of hospital admissions because of lower respiratory tract infections in the world. We evaluated the prevalence of reduced ventilation in houses in Nunavut, Canada, and whether this was associated with an increased risk of these infections among young Inuit children.
We measured ventilation in 49 homes of Inuit children less than 5 years of age in Qikiqtaaluk (Baffin) Region, Nunavut. We identified the occurrence of lower respiratory tract infections using a standardized questionnaire. Associations between ventilation measures and lower respiratory tract infection were evaluated using multiple logistic regression models.
The mean number of occupants per house was 6.1 people. The mean ventilation rate per person was 5.6 L/s (standard deviation [SD] 3.7); 80% (37/46) of the houses had ventilation rates below the recommended rate of 7.5 L/s per person. The mean indoor carbon dioxide (CO2) concentration of 1358 (SD 531) ppm was higher than the recommended target level of 1000 ppm. Smokers were present in 46 homes (94%). Of the 49 children, 27 (55%) had a reported history of lower respiratory tract infection. Reported respiratory infection was significantly associated with mean CO2 levels (odds ratio [OR] 2.85 per 500-ppm increase in mean indoor CO2, 95% confidence interval [CI] 1.23–6.59) and occupancy (OR 1.81 for each additional occupant, 95% CI 1.14–2.86).
Reduced ventilation and crowding may contribute to the observed excess of lower respiratory tract infection among young Inuit children. The benefits of measures to reduce indoor smoking and occupancy rates and to increase ventilation should be studied.
PMCID: PMC1913116  PMID: 17638953

Results 1-8 (8)