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1.  The Pandemic Influenza A (H1N1) 2009 Vaccine Does Not Increase the Mortality Rate of Idiopathic Interstitial Pneumonia: A Matched Case-Control Study 
PLoS ONE  2014;9(2):e88927.
Evidence regarding the mortality rate after administration of the pandemic influenza A (H1N1) 2009 vaccine on patients with underlying diseases is currently scarce. We conducted a case-control study in Japan to compare the mortality rates of patients with idiopathic interstitial pneumonia after the vaccines were administered and were not administered.
Between October 2009 and March 2010, we collected clinical records in Japan and conducted a 1∶1 matched case-control study. Patients with idiopathic interstitial pneumonia who died during this period were considered case patients, and those who survived were considered control patients. We determined and compared the proportion of each group that received the pandemic influenza A (H1N1) 2009 vaccine and estimated the odds ratio. Finally, we conducted simulations that compensated for the shortcomings of the study associated with adjusted severity of idiopathic interstitial pneumonia.
The case and control groups each comprised of 75 patients with idiopathic interstitial pneumonia. The proportion of patients who received the pandemic influenza A (H1N1) 2009 vaccine was 30.7% and 38.7% for the case and control groups, respectively. During that winter, the crude conditional odds ratio of mortality was 0.63 (95% confidence interval, 0.25–1.47) and the adjusted conditional odds ratio was 1.18 (95% confidence interval, 0.33–4.49); neither was significant. The simulation study showed more accurate conditional odds ratios of 0.63–0.71.
In our study, we detected no evidence that the influenza A (H1N1) 2009 vaccine increased the mortality rate of patients with idiopathic interstitial pneumonia. The results, however, are limited by the small sample size and low statistical power. A larger-scale study is required.
PMCID: PMC3934868  PMID: 24586445
2.  Rationale and study design of the Japan environment and children’s study (JECS) 
BMC Public Health  2014;14:25.
There is global concern over significant threats from a wide variety of environmental hazards to which children face. Large-scale and long-term birth cohort studies are needed for better environmental management based on sound science. The primary objective of the Japan Environment and Children’s Study (JECS), a nation-wide birth cohort study that started its recruitment in January 2011, is to elucidate environmental factors that affect children’s health and development.
Approximately 100,000 expecting mothers who live in designated study areas will be recruited over a 3-year period from January 2011. Participating children will be followed until they reach 13 years of age. Exposure to environmental factors will be assessed by chemical analyses of bio-specimens (blood, cord blood, urine, breast milk, and hair), household environment measurements, and computational simulations using monitoring data (e.g. ambient air quality monitoring) as well as questionnaires. JECS’ priority outcomes include reproduction/pregnancy complications, congenital anomalies, neuropsychiatric disorders, immune system disorders, and metabolic/endocrine system disorders. Genetic factors, socioeconomic status, and lifestyle factors will also be examined as covariates and potential confounders. To maximize representativeness, we adopted provider-mediated community-based recruitment.
Through JECS, chemical substances to which children are exposed during the fetal stage or early childhood will be identified. The JECS results will be translated to better risk assessment and management to provide healthy environment for next generations.
PMCID: PMC3893509  PMID: 24410977
Birth cohort; Children; Growth and development; Environmental chemicals; Pregnant women
3.  Multilevel Longitudinal Analysis of Sex Differences in Height Gain and Growth Rate Changes in Japanese School-Aged Children 
Journal of Epidemiology  2013;23(4):275-279.
Determining standard pubertal growth patterns using longitudinal anthropometric measures is important in growth assessment. We used an appropriate repeated-measurements method to identify height growth patterns in Japanese school-aged girls and boys.
The participants were children born during the period from 1991 through 1999 who had entered the first grade of elementary school in the Enzan district in Koshu City, Japan. This study was part of the Project Koshu cohort study. Height was measured annually in April from the first grade of elementary school (age, 6–7 years) to the third grade of junior middle school (age, 14–15 years). Height gain and growth rate trajectories in boys and girls were constructed using multilevel analysis.
In total, 1984 children (1036 boys and 948 girls) were included in this study. Height in boys and girls was similar at age 6.5 to 9.5 years. Girls subsequently grew faster and were taller than boys at age 10.5 to 11.5 years. Starting at age 12.5 years, male height caught up and exceeded female height. Height gain trajectories showed that annual height gain among girls increased slowly and peaked during age 9.5 to 11.5 years, while male height gains declined slightly at first and peaked at age 11.5 to 12.5 years. Sex differences in height gains were significant during the period from age 7.5 to 14.5 years (P < 0.0001). Growth rate and height gain trajectories were similar between sexes.
Sex differences in growth trajectory were significant, and female height gain peaked approximately 2 years earlier than male height gain.
PMCID: PMC3709552  PMID: 23774286
growth pattern; sex; puberty; height gain; growth rate
4.  Access to improved water and its relationship with diarrhoea in Kathmandu Valley, Nepal: a cross-sectional study 
BMJ Open  2013;3(6):e002264.
To assess the associations between diarrhoea and types of water sources, total quantity of water consumed and the quantity of improved water consumed in rapidly growing, highly populated urban areas in developing countries.
Cross-sectional analysis using population-representative secondary data obtained from an interview survey conducted by the Asian Development Bank for the 2009 Kathmandu Valley Water Distribution, Sewerage and Urban Development Project.
Kathmandu Valley, Nepal.
2282 households.
A structured questionnaire was used to collect information from households on the quantity and sources of water consumed; health, socioeconomic and demographic status of households; drinking water treatment practices and toilet facilities.
Family members of 179 households (7.8%) reported having developed diarrhoea during the previous month. For households in which family members consumed less than 100 L of water per capita per day (L/c/d), which is the minimum quantity recommended by WHO, the risk of contracting diarrhoea doubled (1.56-fold to 2.92-fold). In households that used alternative water sources (such as wells, stone spouts and springs) in addition to improved water (provided by a water management authority), the likelihood of contracting diarrhoea was 1.81-fold higher (95% CI 1.00 to 3.29) than in those that used only improved water. However, access to an improved water source was not associated with a lower risk of developing diarrhoea if optimal quantities of water were not consumed (ie, <100 L/c/d). These results were independent of socioeconomic and demographic variables, daily drinking water treatment practices, toilet facilities and residential areas.
Providing access to a sufficient quantity of water—regardless of the source—may be more important in preventing diarrhoea than supplying a limited quantity of improved water.
PMCID: PMC3696862  PMID: 23811169
Diarrhoeal Disease; Social Inequalities; Urbanisation; Water Supply; Nepal; Developing Countries
5.  Developmental Trajectories of Body Mass Index Among Japanese Children and Impact of Maternal Factors during Pregnancy 
PLoS ONE  2012;7(12):e51896.
The aims of this study were to 1) determine the distinct patterns of body mass index (BMI) trajectories in Japanese children, and 2) elucidate the maternal factors during pregnancy, which contribute to the determination of those patterns.
Methodology/Principal Findings
All of the children (1,644 individuals) born in Koshu City, Japan, between 1991 and 1998 were followed in a longitudinal study exploring the subjects’ BMI. The BMI was calculated 11 times for each child between birth and 12 years of age. Exploratory latent class growth analyses were conducted to identify trajectory patterns of the BMI z-scores. The distribution of BMI trajectories were best characterized by a five-group model for boys and a six-group model for girls. The groups were named “stable thin,” “stable average,” “stable high average,” “progressive overweight,” and “progressive obesity” in both sexes; girls were allocated to an additional group called “progressive average.” Multinomial logistic regression found that maternal weight, smoking, and skipping breakfast during pregnancy were associated with children included in the progressive obesity pattern rather than the stable average pattern. These associations were stronger for boys than for girls.
Multiple developmental patterns in Japanese boys and girls were identified, some of which have not been identified in Western countries. Maternal BMI and some unfavorable behaviors during early pregnancy may impact a child’s pattern of body mass development. Further studies to explain the gender and regional differences that were identified are warranted, as these may be important for early life prevention of weight-associated health problems.
PMCID: PMC3521723  PMID: 23272187
6.  Prevalence of birth defects and risk-factor analysis from a population-based survey in Inner Mongolia, China 
BMC Pediatrics  2012;12:125.
Birth Defects are a series of diseases that seriously affect children's health. Birth defects are generally caused by several interrelated factors. The aims of the article is to estimate the prevalence rate and types of birth defects in Inner Mongolia, China, to compare socio-demographic characteristics among the children with birth defects and to analyze the association between risk factors and birth defects.
Data used in this study were obtained through baseline survey of Inner Mongolia Birth Defects Program, a population-based survey conducted from 2005 to 2008. The survey used cluster sampling method in all 12 administrative districts of Inner Mongolia. Sampling size is calculated according to local population size at a certain percentage. All live births, stillbirths and abortions born from October 2005 to September 2008, whose families lived in Inner Mongolia at least one year, were included. The cases of birth defects were diagnosed by the clinical doctors according to their experiences with further laboratory tests if needed. The inclusion criteria of the cases that had already dead were decided according to death records available at local cites. We calculated prevalence rate and 95% confidence intervals of different groups. Outcome variable was the occurrence of birth defects and associations between risk factors and birth defects were analyzed by using Poisson regression analysis.
976 children with birth defects were diagnosed. The prevalence rate of birth defects was 156.1 per 10000 births (95%CI: 146.3-165.8). The prevalence rate of neural tube defect (20.1 per 10000 births) including anencephaly(6.9 per 10000), spina bifida (10.6 per 10000), and encephalocele (2.7 per 10000) was the highest, followed by congenital heart disease (17.1 per 10000). The relative risk (RR) for maternal age less than 25 was 2.22 (95%CI: 2.05, 2.41). The RR of the ethnic Mongols was lower than Han Chinese (RR: 0.84; 95%CI: 0.80-0.89). The RR of the third and second pregnancy was significantly higher than the first pregnancy while a slight difference between the second and the first pregnancy was also found. Alcohol drinking of mothers, familial inheritance and living area were also found to be related to the occurrence of the birth defects.
Relatively higher birth defect rates were found in Inner Mongolia. This study found that maternal age less than 25, alcohol drinking, familiar inheritance, lower education level of mothers, times of pregnancies and living in rural areas may increase the risk of birth defects. Ethnic Mongols were less likely to have birth defects than Han Chinese.
PMCID: PMC3473296  PMID: 22900612
Birth defects; Prevalence rate; Relative risk; Risk factors
7.  Early impact of depression symptoms on the decline in activities of daily living among older Japanese: Y-HALE cohort study 
It is well known that depression deteriorates basic activities of daily living (ADLs), such as eating and bathing, among the elderly, but little is known about the early impact of depression symptoms on the next higher level of functioning, namely higher-levels ADLs, such as instrumental self-maintenance, intellectual activities, and social roles. The objective of this study was to determine whether symptoms of depression are associated with a subsequent decline in higher-level ADLs within a 12-month period of time.
The study cohort consisted of a random sample of 587 non-institutionalized adults aged ≥65 years living in Yamanashi prefecture, Japan. The baseline survey was conducted in 2003. After 12 months, a mailed follow-up survey evaluated changes in higher-level ADLs (follow-up rate 98.6%).
After adjusting for sociodemographic and behavioral confounders, logistic regression indicated that baseline severe depression symptoms were associated with a 3.2-fold (95% confidence interval 1.6–6.3) higher chance of a subsequent decline in higher-level ADLs compared to those without severe depression symptoms. The presence of severe depression symptoms was selected by stepwise logistic regression in all models, except for the model with intellectual activities as an outcome, while other lifestyle factors were not selected.
Symptoms of severe depression may adversely affect higher-level ADLs even in a relatively short time-frame. In addition, the early effects of depression symptoms may be stronger than those of other traditional lifestyle risk factors. Monitoring a wide range of ADLs in elderly individuals showing signs of depression may be important to prevent a functional decline in health and the need for long-term care.
PMCID: PMC3078288  PMID: 21431794
Japan; Mental health; Aged; Depression; Disability
8.  Maternal Smoking During Pregnancy and Childhood Growth Trajectory: A Random Effects Regression Analysis 
Journal of Epidemiology  2012;22(2):175-178.
Although maternal smoking during pregnancy has been reported to have an effect on childhood overweight/obesity, the impact of maternal smoking on the trajectory of the body mass of their offspring is not very clear. Previously, we investigated this effect by using a fixed-effect model. However, this analysis was limited because it rounded and categorized the age of the children. Therefore, we used a random-effects hierarchical linear regression model in the present study.
The study population comprised children born between 1 April 1991 and 31 March 1999 in Koshu City, Japan and their mothers. Maternal smoking during early pregnancy was the exposure studied. The body mass index (BMI) z-score trajectory of children born to smoking and non-smoking mothers, by gender, was used as the outcome. We modeled BMI trajectory using a 2-level random intercept and slope regression.
The participating mothers delivered 1619 babies during the study period. For male children, there was very strong evidence that the effect of age in months on the increase in BMI z-score was enhanced by maternal smoking during pregnancy (P < 0.0001). In contrast, for female children, there was only weak evidence for an interaction between age in months and maternal smoking during pregnancy (P = 0.054), which suggests that the effect of maternal smoking during pregnancy on the early-life BMI trajectory of offspring differed by gender.
These results may be valuable for exploring the mechanism of fetal programming and might therefore be clinically important.
PMCID: PMC3798597  PMID: 22277789
body mass index; childhood growth; gender; multi-level analysis; pregnancy; smoking
9.  Effect of educational intervention using the Internet on quantitative ultrasound parameters in prevention of osteoporosis: a randomized controlled trial in young Japanese women 
The objective of this study was to determine whether or not educational intervention using the Internet, to prevent osteoporosis, is able to increase bone strength in young women.
Subjects were 253 healthy female university and junior college students aged 18–25 years. After initial measurements of bone stiffness index, a bone formation marker, and a bone absorption marker, the minimization method was used to allocate the subjects to an intervention group (n = 126) or a control group (n = 127) according to whether the measurements were above or below average. Subjects in the intervention group were instructed to perform osteoporosis prevention activities, ie, jump on the spot as high as possible ten times per day and increase calcium intake by 300 mg per day to a total of 800 mg or more per day on average. In addition, they were instructed to report the implementation status of the recommended measures via email. The researcher sent out information on osteoporosis and preventive behaviors to the subjects five times via email.
A total of 182 subjects, comprising 87 (69.0%) in the intervention group and 95 (74.8%) in the control group, underwent remeasurement 6 months later. Of the subjects in the intervention group, 54 (42.9%) reported their daily additional calcium intake amount and number of jumps via email. The mean amount of additional calcium taken was 216.3 ± 85.9 mg per day, and mean number of jumps performed was 6.4 ± 4.2 per day. Subjects in the intervention group were further divided into an implementation group (n = 54), consisting of subjects who sent in reports and a nonimplementation group (n = 72) who did not. No significant difference was found among the groups for rate of change in bone stiffness index and speed of sound, but there was a significant difference for broadband ultrasound attenuation (BUA) (P = 0.017). Sheffe’s multiple comparison test was performed using baseline body weight and BUA values as covariates, and revealed that the rate of decrease in bone strength in the control group was larger than that in the implementation group (P = 0.049).
Health education for preventing osteoporosis via Internet email was performed over 6 months for women aged 18 to 25 and a comparison was performed between the intervention group and control group. The intervention consisted of high jumps on the spot (ten times a day), which reduced the drop in BUA, and thus indicates robustness of the trabecular structure. This suggests that a longer intervention period may maintain or improve bone strength.
PMCID: PMC3256942  PMID: 22247627
prevention; osteoporosis; Internet; ultrasound; Japanese; women
10.  Risk Perception of Pregnancy Promotes Disapproval of Gestational Surrogacy: Analysis of a Nationally Representative Opinion Survey in Japan 
To clarify the relationship between the general attitude towards gestational surrogacy and risk perception about pregnancy and infertility treatment.
Materials and Methods
This study analysed the data of nationally representative cross-sectional surveys from 2007 concerning assisted reproductive technologies. The participants represented the general Japanese population. We used this data to carry out multivariate analysis. The main outcome measures were adjusted odds ratios and 95% confidence intervals from logistic regression models for factors including the effect of pregnancy risk perception on the attitude toward gestational surrogacy.
In this survey, 3412 participants responded (response rate of 68.2%). With regard to the attitude towards gestational surrogacy, 54.0% of the respondents approved of it, and 29.7% stated that they were undecided. The perception of a high level of risk concerning ectopic pregnancy, threatened miscarriage or premature birth, and pregnancy-induced hypertension influenced the participants’ attitudes towards gestational surrogacy. Moreover, this perception of risk also contributed to a disapproval of the technique.
Our findings suggest that a person who understands the risks associated with pregnancy might clearly express their disapproval of gestational surrogacy.
PMCID: PMC4059953  PMID: 24963363
Risk Assessment; Surrogate Mothers; Public Opinion; Infertility; Gestational Pregnancy
11.  Utility of Subjective Sleep Assessment Tools for Healthy Preschool Children: A Comparative Study Between Sleep Logs, Questionnaires, and Actigraphy 
Journal of Epidemiology  2010;20(2):143-149.
Sleep pattern is an important factor in a child’s mental, behavioural and physical status. To evaluate the sleep patterns of children, subjective tools such as sleep logs and questionnaires are still widely used in addition to objective methods of sleep assessment. Despite the established correlation between subjective and objective sleep variables, the characteristic features of subjective assessment have not been elucidated.
To investigate the characteristics of parental sleep assessment (daily sleep log and brief questionnaire) in preschool children, a 7-day actigraphic sleep study was conducted in 48 healthy 5-year-old children.
Sleep schedule variables in the parental reports generally correlated well with actigraphic assessment of sleep patterns; however, sleep periods were longer in parental reports than in actigraphic recordings. Although the daily sleep log was better correlated with actigraphy, the brief questionnaire showed a good correlation with sleep pattern on weekday actigraphic assessments. Parental reports recorded fewer than 10% of the night wakings recorded by actigraphy.
Subjective sleep assessments remain useful, although their utility depends on the purpose and size of the study in question. However, knowledge of the potential biases and characteristics of such assessments is essential for correct interpretation of the data.
PMCID: PMC3900813  PMID: 20139658
actigraphy; sleep log; questionnaire; preschool child; sleep pattern; subjective sleep assessment; parental report
12.  Early Television Exposure and Children’s Behavioral and Social Outcomes at Age 30 Months 
Journal of Epidemiology  2010;20(Suppl 2):S482-S489.
Previous research has suggested that television (TV) viewing may be associated with increased behavioral and emotional problems in children. However, there are few prospective studies targeted for its association with outcomes of children under 3 years old. The purpose of this study was to exam the association between children’s early TV exposure at ages 18 and 30 months and the behavioral and emotional outcomes at age 30 months.
We analyzed data collected prospectively in the Japan Children’s Study. TV exposure was assessed by mothers’ report at infant ages of 18 and 30 months. The outcomes were assessed using the Strengths and Difficulties Questionnaire (SDQ). Analysis of Covariance was used to estimate the effect of TV exposure on behavioral and emotional outcomes.
The percentage of children who watched TV 4 hours or more per day was 29.4% at age 18 months, 24.5% at age 30 months, and 21% at both ages. Hyperactivity–inattention at age 30 months was positively associated with TV exposure at age 18 months, whereas prosocial behavior was negatively associated with hours of exposure even after adjustment. However, there were no significant differences in SDQ subscales according to daily hours of TV viewing at age 30 months.
Daily TV exposure at age 18 months was associated with hyperactivity–inattention and prosocial behavior at age 30 months. However, the directly casual relation was not proved in the present study. Additional research considering the TV program content and exposure timing are needed to investigate the causal relation between TV viewing and behavioral outcome.
PMCID: PMC3920399  PMID: 20179364
children; television viewing; behavioral outcomes; prosocial behavior
13.  Overview of the Japan Children’s Study 2004–2009; Cohort Study of Early Childhood Development 
Journal of Epidemiology  2010;20(Suppl 2):S397-S403.
There are still a lot of unknown aspects about the childhood development of sociability which are based on neuroscientific basis. Purpose of the Japan Children’s Study (JCS) was to verify the normal process of child development of sociability; the trajectory and factors related development of sociability, and to collect findings and integrate the knowledge to make the plan of long-term and large scale cohort study.
A child cohort study underway in Japan since 2005. There are the cohort study including a infant cohort study at age of 4 months to 30 months and a preschool cohort study at age of 5 years old to 8 years old. Questionnaires, direct observation of children and cognitive testing were performed.
In infant cohort study, 465 infants were recruited at 4 months and 367 children were followed up to 30 months, follow up rate was 78.9% and in the preschool cohort study, total 192 children (112 at 2005 and 80 at 2007) at age of 5 years old and 169 followed up to 6 years (follow up rate was 88.0%), and 79 children were followed up to 8 years old (follow up rate was 70.5%) old. Several new measurements to evaluate child sociability were developed. Some factors related to development of child sociability were found for example the ‘praise’ was related to child sociability in cohort study based on neuroscience findings.
Though the trajectory of child sociability development were not clarified, some significant factors related to development of sociability, and the basic findings to conduct a long-term and large scale cohort study were provided.
PMCID: PMC3920403  PMID: 20179361
sociability; development; cohort study; neuroscience
14.  Comparison of Factors Contributing to Developmental Attainment of Children between 9 and 18 Months 
Journal of Epidemiology  2010;20(Suppl 2):S452-S458.
Little is known about how contributing factors of development change during early childhood in Japan. The aim of this study was to investigate the factors that contributed to the developmental attainment of children between 9 and 18 months of age using prospective longitudinal data from a developmental cohort study.
We used data from observations at 3 time points (at infant age of 4, 9 and 18 months) in the Japan Children’s Study. Mothers were administered questionnaires that requested information about their child’s perinatal outcomes, temperament, family structure, family income, parental education, parenting stress, and child-rearing environment at home. At 9 and 18 months, mothers completed the Kinder Infant Development Scale to evaluate their child’s development.
A total of 284 children were available for analysis. Female children and children having siblings had higher probability of attaining developmental norms at 18 months than male and only children. Birth weight, gestational age, and temperament were associated with development at 9 months, but the effects of gestational age and temperament on development disappeared at 18 months. Stimulation from the mother at 9 months was not only related to development at that age but also promoted development at 18 months.
Our findings suggest that the role of family environmental factors such as early mother’s stimulation and sibling’s existence in development during early childhood might become more important as the child gets older.
PMCID: PMC3920408  PMID: 20179366
child development; environmental factors; parenting stress; prospective study
15.  Do social comparisons explain the association between income inequality and health?: Relative deprivation and perceived health among male and female Japanese individuals 
Social science & medicine (1982)  2008;67(6):982-987.
Relative deprivation has been hypothesized as one of the pathways accounting for the link between income inequality and health. We tested this hypothesis in a large national sample of men and women in Japan. Our survey included a probability sample of 22,871 men and 24,243 women aged 25–64, from whom information was gathered on demographic variables, household income, occupation or employment status, and self-rated health. Our measure of relative deprivation was the Yitzhaki Index, which calculates the deprivation suffered by each individual as a function of the aggregate income shortfall for each person relative to everyone else with higher incomes in that person’s reference group. We modeled several alternative reference groups, including others with the same occupation, others of the same age group, and others living in the same geographic area (prefecture), as well as combinations of these. Generalized estimating equations demonstrated that higher relative deprivation was associated with worse self-rated health. Even after controlling for absolute income as well as other sociodemographic factors, the odds ratio and its 95% confidence intervals (CI) for poor health ranged from 1.09 (95% CI: 1.02–1.16) to 1.18 (95% CI: 1.11–1.26) for men and from 1.10 (95% CI: 1.04–1.16) to 1.16 (95% CI: 1.09–1.23) for women per 1 million increase in the Yitzhaki Index. As such, relative income deprivation is associated with poor self-rated health independently of absolute income, and relative deprivation may be a mechanism underlying the link between income inequality and population health.
PMCID: PMC2791046  PMID: 18632196
Japan; Psychosocial deprivation; Relative deprivation; Income inequality; Pathways
16.  Income inequality, mortality, and self rated health: meta-analysis of multilevel studies 
Objective To provide quantitative evaluations on the association between income inequality and health.
Design Random effects meta-analyses, calculating the overall relative risk for subsequent mortality among prospective cohort studies and the overall odds ratio for poor self rated health among cross sectional studies.
Data sources PubMed, the ISI Web of Science, and the National Bureau for Economic Research database.
Review methods Peer reviewed papers with multilevel data.
Results The meta-analysis included 59 509 857 subjects in nine cohort studies and 1 280 211 subjects in 19 cross sectional studies. The overall cohort relative risk and cross sectional odds ratio (95% confidence intervals) per 0.05 unit increase in Gini coefficient, a measure of income inequality, was 1.08 (1.06 to 1.10) and 1.04 (1.02 to 1.06), respectively. Meta-regressions showed stronger associations between income inequality and the health outcomes among studies with higher Gini (≥0.3), conducted with data after 1990, with longer duration of follow-up (>7 years), and incorporating time lags between income inequality and outcomes. By contrast, analyses accounting for unmeasured regional characteristics showed a weaker association between income inequality and health.
Conclusions The results suggest a modest adverse effect of income inequality on health, although the population impact might be larger if the association is truly causal. The results also support the threshold effect hypothesis, which posits the existence of a threshold of income inequality beyond which adverse impacts on health begin to emerge. The findings need to be interpreted with caution given the heterogeneity between studies, as well as the attenuation of the risk estimates in analyses that attempted to control for the unmeasured characteristics of areas with high levels of income inequality.
PMCID: PMC2776131  PMID: 19903981
17.  Contribution of Parenting Factors to the Developmental Attainment of 9-Month-Old Infants: Results From the Japan Children’s Study 
Journal of Epidemiology  2009;19(6):319-327.
Child development integrates several interdependent domains, but few studies have attempted to identify the common factors that contribute to these different domains of development in infancy. The aim of the present study was to identify the factors that contribute to several domains of developmental attainment in 9-month-old infants.
We used data from the Japan Children’s Study, a prospective cohort study underway in Japan since 2005. Mothers completed questionnaires about their children’s temperament, coparenting behaviors, maternal parenting stress, and parenting behavior. The Kinder infant development scale was used to evaluate child development outcomes.
A total of 270 children were included in this analysis. After adjusting for the children’s birth weight, gestational age, temperament, and other family environmental variables, multiple logistic regression analyses showed that greater maternal cognitive stimulation was associated with the development of receptive language, expressive language, social relationships, and feeding. Results also suggest that early supportive coparenting helped to promote development in manipulation, receptive language, and social relationships. Maternal parenting stress was stable between the infant ages of 4 and 9 months and was negatively correlated with scores for coparenting and maternal stimulation, which suggests an indirect effect of maternal parenting stress on child outcomes.
Supportive coparenting and maternal cognitive stimulation were the most important contributors to most domains of child development. Our findings suggest that educational interventions targeting young families would help parents establish and maintain an environment of successful coparenting and cognitive stimulation as their children grow.
PMCID: PMC3924101  PMID: 19776496
development; coparenting; maternal stimulation; parenting stress; prospective study
18.  The Association between Maternal Smoking during Pregnancy and Childhood Obesity Persists to the Age of 9–10 Years 
Journal of Epidemiology  2009;19(3):136-142.
We previously reported that a number of factors related to maternal lifestyle during early pregnancy, including smoking, are associated with childhood obesity at 5 years of age. In the present study, we investigated whether the association with maternal smoking persisted to the age of 9–10 years.
The study population comprised children born between April 1, 1991 and March 31, 1999, and their mothers. The dependent variables—childhood overweight and obesity at 5 and 9–10 years of age—were defined according to internationally acknowledged cut-off values. Maternal smoking during early pregnancy was used as the independent variable.
Mothers who completed a specifically designed questionnaire gave birth to a total of 1644 infants during the study period. Anthropometric data were collected from 1302 of these children during medical checkups at 9–10 years of age (follow-up rate: 79.2%). Maternal smoking during early pregnancy was associated with obesity in 9- to 10-year-old children (adjusted odds ratio, 1.91; 95% confidence interval, 1.03–3.53). However, the point estimates at the age of 9–10 years were considerably lower than those at the age of 5 years.
Our results suggest that fetal environment, including exposure to maternal smoking, continues to be associated with childhood obesity at the age of 9–10 years.
PMCID: PMC3924138  PMID: 19398848
smoking; pregnancy; life styles; obesity; fetal programming
19.  Lack of association between p53 gene polymorphisms and primary open angle glaucoma in the Japanese population 
Molecular Vision  2009;15:1045-1049.
To assess whether tumor protein p53 gene (p53) polymorphisms are associated with primary open angle glaucoma (POAG) in the Japanese population.
Four hundred and twenty-five Japanese patients with POAG, including normal tension glaucoma (NTG, n=213) and high tension glaucoma (HTG, n=212) and 189 control subjects without glaucoma were analyzed for two p53 polymorphisms (rs1042522; a G→C substitution at codon 72 in exon 4 and rs59758982; a 16 base pair insertion in intron 3) using allele specific primer PCR and a pyrosequencing technique respectively. The genotypic and allelic frequencies were compared between NTG or HTG patients and control subjects.
No significant difference (NTG versus control, p=0.99, and HTG versus control, p=0.69, χ2 test) was observed regarding the p53 genotype frequencies at codon 72 between the NTG (GG: 43.2%, GC: 44.6%, CC: 12.2%) or HTG (GG: 40.1%, GC: 48.1%, CC: 11.8%) patients and the control subjects (GG: 43.9%, GC: 43.9%, CC: 12.2%). In addition, there was no significant difference (NTG versus control, p=0.94; and HTG versus control, p=0.66, Fisher's exact test) in the p53 allele frequencies at codon 72 between the NTG (G allele: 65.5%, C allele: 34.5%) or HTG (G allele: 64.2%, C allele: 35.8%) patients and the control subjects (G allele: 65.9%, C allele: 34.1%). No 16 base pair insertion in intron 3 was found in this study.
p53 polymorphisms were not associated with POAG in the Japanese population. Further studies in the other ethnic populations should therefore be performed to elucidate whether the p53 intron 3 insertion polymorphism is a genetic risk factor for POAG, because the intron 3 insertion polymorphism occurs very rarely in the Japanese population.
PMCID: PMC2684750  PMID: 19471604
20.  Lysyl oxidase-like 1 gene polymorphisms in Japanese patients with primary open angle glaucoma and exfoliation syndrome 
Molecular Vision  2008;14:1303-1308.
To assess whether lysyl oxidase-like 1 (LOXL1) polymorphisms are associated with primary open-angle glaucoma (POAG) and exfoliation syndrome (XFS).
Japanese patients with POAG (n=213) or XFS (n=89) and 191 control subjects were analyzed for LOXL1 polymorphisms (rs1048661: 758G/T, Arg141Leu and rs3825942: 794G/A, Gly153Asp). Demographic and clinical features of POAG patients and control subjects were compared in terms of the TT/GG compound genotype of rs1048661 and rs3825942.
There was a significant difference in the genotype frequencies between XFS patients and control subjects (p<0.0001). Frequencies of the T allele of rs1048661 and the G allele of rs3825942 were significantly higher in XFS patients than in control subjects (rs1048661: 99.4% versus 55.0%; rs3825942: 99.4% versus 85.3%; p<0.0001). Except for one who had the TG/AG compound genotype, all XFS patients had the TT/GG compound genotype. An almost 250 fold increase in the risk of XFS (p<0.0001; odds ratio: 252.2; 95% confidence interval: 32.7 to more than 1000) was found in patients with the TT/GG compound genotype compared to those without the genotype. There were no significant differences in the genotype and allele frequencies between POAG patients and control subjects. Furthermore, no significant differences were noted in the demographic and clinical features of POAG patients as well as control subjects with and without the TT/GG high-risk compound genotype.
LOXL1 polymorphisms were associated with XFS. However, the frequencies of the polymorphisms differed between Japanese and Caucasian XFS patients. These polymorphisms had no influence on the phenotypic features of POAG patients.
PMCID: PMC2464611  PMID: 18636115
21.  Musculoskeletal disorders among staff in South Korea’s largest nursing home 
Although musculoskeletal disorders (MSD) represent a significant occupational issue for most nursing home staff, few epidemiological studies have been conducted in Korea.
We investigated the prevalence of, and risk factors for, MSD within South Korea’s largest nursing home using a previously validated, self-reporting questionnaire.
From a total of 130 registered employees, 91 (70.0%) successfully completed questionnaires were obtained. The majority were female (80.2%, n=73), with an age range of 27 to 62 years and an average age of 47.0 years (SD 8.0). MSD occurred in varying amounts and was classified into distinct categories depending on body site. The most commonly affected region was the shoulder (reported by 35.2%), followed by the arm (22.0%), knee (20.9%) and lower back (19.8%). Three statistically significant risk factors were consistently identified among all 4 MSD sites: manually handling patients (OR 5.1 to 20.8), changing a patient’s clothes (OR 6.7 to 30.1) and working as a nursing aide (OR 3.7 to 74.3).
Overall, the present results suggest that employment within a South Korean nursing home incurs certain hazards depending on job description and daily work tasks. The MSD prevalence differed from other occupations within South Korea and previous nursing home studies.
PMCID: PMC2723262  PMID: 21432112
musculoskeletal disorders; nursing home; Korea; low back pain; self-reported

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