The APE1 Asp/Asp Genotype and the Combination of APE1 Asp/Asp and hOGG1-Cys Variants Are Associated With Increased p53 Mutation in Non–Small Cell Lung Cancer

Background

The hOGG1 Ser326Cys polymorphism is associated with lung cancer risk, but there are limited data regarding an association between the APE1 Asp148Glu polymorphism and lung cancer. Biological evidence shows that the hOGG1-Cys allele results in less DNA repair activity; however, this is not associated with p53 mutation in lung cancer. Therefore, we investigated whether an interaction between hOGG1 and APE1 is associated with the frequency of p53 mutation in lung cancer.

Methods

We studied 217 Taiwanese adults with primary lung cancer. DNA polymorphisms of hOGG1 and APE1 were determined by polymerase chain reaction (PCR)-based restriction fragment length polymorphism. Mutations in p53 exons 5–8 were detected by direct sequencing. Multiple logistic regression was used to estimate odds ratios (ORs) and 95% CIs for the risk of p53 mutation associated with polymorphisms of hOGG1 and APE1 in lung cancer.

Results

As expected, no association between hOGG1 polymorphism and p53 mutation was observed in this population. However, a higher risk of p53 mutation was found in participants with the APE1 Asp/Asp genotype than in those with the APE1-Glu allele (OR, 2.15; 95% CI, 1.19–3.87; P = 0.011). The risk of p53 mutation was also higher in participants with APE1 Asp/Asp plus hOGG1-Cys than in those with APE1-Glu plus hOGG1 Ser/Ser (OR, 3.72; 95% CI, 1.33–10.40; P = 0.012).

Conclusions

These results suggest that the APE1 Asp/Asp genotype and the combination of the APE1 Asp/Asp and hOGG1-Cys variants are associated with increased risk of p53 mutation in non–small cell lung cancer.Key words: hOGG1 Ser326Cys, APE1 Asp148Glu, p53 mutation, NSCLC     

Association between Interleukin-1B C-31T Polymorphism and Obesity in Japanese

Background

Recent studies have revealed a close relationship between obesity and polymorphism in the inflammation gene. However, the association between interleukin-1beta (IL-1β) and obesity remains controversial. We therefore investigated the association between IL-1B C-31T polymorphism and obesity in Japanese.

Methods

The participants were 802 inhabitants (281 men and 521 women) of Japan, aged 39 to 88 years, who attended a health examination in 2003. Body height, weight, waist and hip circumferences, and body fat percentage were measured. The IL-1B C-31T polymorphism was genotyped by polymerase chain reaction with confronting 2-pair primers. The association between IL-1B C-31T genotypes and various indices of obesity was then investigated. The confounding factor-adjusted odds ratios (OR) and 95% confidence intervals (CI) for obesity were calculated for each IL-1B C-31T genotype by using unconditional logistic regression analysis.

Results

Among male carriers of the CT and TT genotypes, the ORs for high body fat percentage were 2.58 (95% CI, 1.17–6.34) and 2.81 (1.17–7.33), respectively, as compared to carriers of the CC genotype (P for trend = 0.037). Among women, carriers of the TT genotype had significantly higher ORs for high BMI (OR, 2.13; 95% CI, 1.25–3.67) and large waist circumference (2.49; 1.37–4.66), as compared to women with the CC genotype (P for trend = 0.005 and 0.004, respectively).

Conclusions

The IL-1B C-31T polymorphism is associated with obesity in Japanese. Men and women with the TT genotype of IL-1B C-31T had a higher risk for obesity than those with the CC genotype.Key words: interleukin-1beta, obesity, polymorphism, Japanese     

Peer Reviewed: State Requirements and Recommendations for School-Based Screenings for Body Mass Index or Body Composition, 2010

Introduction

We present a comprehensive picture of state requirements and recommendations for body mass index (BMI) and body composition screening of children and explore the association between pediatric obesity prevalence and state screening policies.

Methods

Researchers completed telephone interviews with contacts at the departments of education for all 50 states and reviewed state content standards for physical education.

Results

Twenty states (40%) require BMI or body composition screening, and 9 states (18%) recommend BMI screening or a formal fitness assessment that includes a body composition component. The prevalence of adolescent obesity was higher in states that require BMI screening or fitness assessments with body composition than in states without requirements (16.7% vs 13.6%, P = .001).

Conclusion

Future studies should evaluate the effect and cost-effectiveness of BMI and body composition screening on child obesity.     

Association Between Socioeconomic Status and Obesity in Adults: Evidence From the 2001 to 2009 Korea National Health and Nutrition Examination Survey

Objectives

The present study examined relationships between socioeconomic status (SES) and obesity and body mass index (BMI) as well as the effects of health-related behavioral and psychological factors on the relationships.

Methods

A cross-sectional population-based study was conducted on Korean adults aged 20 to 79 years using data from the 2001, 2005, and 2007 to 2009 Korea National Health and Nutrition Examination Survey. Multivariate logistic and linear regression models were used to estimate odds ratios of obesity and mean differences in BMI, respectively, across SES levels after controlling for health-related behavioral and psychological factors.

Results

We observed significant gender-specific relationships of SES with obesity and BMI after adjusting for all covariates. In men, income, but not education, showed a slightly positive association with BMI (p<0.05 in 2001 and 2005). In women, education, but not income, was inversely associated with both obesity and BMI (p<0.0001 in all datasets). These relationships were attenuated with adjusting for health-related behavioral factors, not for psychological factors.

Conclusions

Results confirmed gender-specific disparities in the associations of SES with obesity and BMI among adult Korean population. Focusing on intervention for health-related behaviors may be effective to reduce social inequalities in obesity.     

Social Network Characteristics and Body Mass Index in an Elderly Korean Population

Objectives

Research has shown that obesity appears to spread through social ties. However, the association between other characteristics of social networks and obesity is unclear. This study aimed to identify the association between social network characteristics and body mass index (BMI, kg/m²) in an elderly Korean population.

Methods

This cross-sectional study analyzed data from 657 Koreans (273 men, 384 women) aged 60 years or older who participated in the Korean Social Life, Health, and Aging Project. Network size is a count of the number of friends. Density of communication network is the number of connections in the social network reported as a fraction of the total links possible in the personal (ego-centric) network. Average frequency of communication (or meeting) measures how often network members communicate (or meet) each other. The association of each social network measure with BMI was investigated by multiple linear regression analysis.

Results

After adjusting for potential confounders, the men with lower density (<0.71) and higher network size (4-6) had the higher BMI (β=1.089, p=0.037) compared to the men with higher density (>0.83) and lower size (1-2), but not in the women (p=0.393). The lowest tertile of communication frequency was associated with higher BMI in the women (β=0.885, p=0.049), but not in the men (p=0.140).

Conclusions

Our study suggests that social network structure (network size and density) and activation (communication frequency and meeting frequency) are associated with obesity among the elderly. There may also be gender differences in this association.     

Association of Peroxisome Proliferator-Activated Receptor α/δ/γ With Obesity,and Gene–Gene Interaction,in the Chinese Han Population

Background

We investigated the association of 10 single-nucleotide polymorphisms (SNPs) in the peroxisome proliferator-activated receptors (PPARs) with obesity and the additional role of gene–gene interaction.

Methods

Participants were recruited within the framework of the Prevention of Multiple Metabolic Disorders and MS in Jiangsu Province cohort population survey of an urban community in China. In total, 820 subjects (513 nonobese adults, 307 obese adults) were randomly selected, and no individuals were consanguineous. Ten SNPs (rs135539, rs4253778, rs1800206, rs2016520, rs9794, rs10865710, rs1805192, rs709158, rs3856806, and rs4684847) were genotyped and analyzed.

Results

After covariate adjustment, minor alleles of rs2016520 in PPARδ and rs10865170 in PPARγ were associated with lower BMI (P < 0.01 for all). Generalized multifactor dimensionality reduction analysis showed significant gene–gene interaction among rs2016520, rs9794, and rs10865170 in 3-dimensional models (P = 0.0010); prediction accuracy was 0.6011 and cross-validation consistency was 9/10. It also showed significant gene–gene interaction between rs2016520 and rs10865170 in all 2-dimensional models (P = 0.0010); prediction accuracy was 0.6072 and cross-validation consistency was 9/10.

Conclusions

rs2016520 and rs10865170 were associated with lower obesity risk. In addition, interaction was identified among rs2016520, rs9794, and rs10865170 in obesity.Key words: peroxisome proliferator-activated receptors, polymorphism, BMI, interaction     

Peer Reviewed: Associations Between Severe Obesity and Depression: Results From the National Health and Nutrition Examination Survey, 2005-2006

Introduction

My objectives were to investigate the association between obesity and depression in a representative sample of American adults, investigate sex and severity of obesity as modifiers of the association between depression and body mass index, determine whether large waist circumference is associated with depression, and explore whether specific health behaviors and poor physical health are possible mediators of the association between obesity and depression, if found.

Methods

The sample consisted of 3,599 nonpregnant adults aged 20 years or older from the National Health and Nutrition Examination Survey, 2005-2006. I operationalized obesity as body mass index (BMI) and waist circumference from the anthropometric measurements of participants and current depression from Patient Health Questionnaire (PHQ-9) scores. I ran logistic regression models with depression as the dependent variable.

Results

In unadjusted analyses, large waist circumference (≥88 cm for women and ≥102 cm for men) and class III obesity (BMI ≥40 kg/m²) were associated with higher prevalence of depression in women only. All of these associations dramatically weakened after adjusting for demographic factors, self-rated health status, and number of chronic conditions.

Conclusion

These findings support an association between depression and obesity in women who are severely obese. Future studies should investigate poor physical health as a possible mediator of the association between obesity and depression in this population of women.     

Weight gain during adulthood and body weight at age 20 are associated with the risk of endometrial cancer in Japanese women

Background

Current obesity is an established risk factor for endometrial cancer; however, the roles of weight gain during adulthood and obesity in early adulthood on endometrial cancer have not been elucidated. Here, we conducted a case-control study comprising 222 histologically diagnosed incident endometrial cancer cases and 2162 age- and menstrual-status matched non-cancer controls.

Methods

Information on current body weight, weight and height at age 20 years, and lifestyle/environmental factors was obtained from a self-administered questionnaire. Subjects were classified into 3 groups according to change in body mass index (BMI, kg/m²) from age 20 years to enrollment (≤0 [reference], 0–3, and >3 kg/m²). The effects of adult BMI change and obesity in early adulthood were evaluated using an unconditional logistic regression model adjusted for potential confounders.

Results

A high BMI at age 20 (BMI ≥25, BMI <25 as reference) was significantly positively associated with endometrial cancer risk (P = 0.005), as was a BMI increase during adulthood (0–3 BMI change, multivariate odds ratio [OR] = 1.28, 95% confidence interval [CI] = 0.88–1.87; >3 BMI change, OR = 2.02, 95% CI = 1.38–2.96; P-trend < 0.001). Parity and BMI at age 20 appeared to modify the effect of weight gain on cancer risk, albeit without statistical significance. This positive association of weight gain with risk was observed only for endometrioid adenocarcinoma.

Conclusions

The results show that endometrial cancer is positively associated with obesity at age 20 and weight gain during adulthood among Japanese women.Key words: endometrial cancer, weight gain, case-control study     

Obesity/Weight Gain and Breast Cancer Risk: Findings From the Japan Collaborative Cohort Study for the Evaluation of Cancer Risk

Background

We analyzed data from the Japan Collaborative Cohort Study (36 164 women aged 40–79 years at baseline in 1988–1990 with no previous diagnosis of breast cancer and available information on weight and height) to examine the association between baseline body mass index (BMI)/weight gain from age 20 years and breast cancer risk in a non-Western population.

Methods

The participants were followed prospectively from enrollment until 1999–2003 (median follow-up: 12.3 years). During follow-up, breast cancer incidence was mainly confirmed through record linkage to population-based cancer registries. A Cox proportional hazards model was used to calculate hazard ratios (HRs) and 95% CIs for the association between breast cancer risk and body size.

Results

In 397 644.1 person-years of follow-up, we identified 234 breast cancer cases. Among postmenopausal women, the adjusted HR increased with BMI, with a significant linear trend (P < 0.0001). Risk was significantly increased among women with a BMI of 24 or higher (HR: 1.50, 95% CI: 1.09–2.08 for BMI of 24–28.9, and 2.13, 1.09–4.16 for BMI ≥ 29) as compared with women with a BMI of 20 to 23.9. Weight gain after age 20 years and consequent overweight/obesity were combined risk factors for postmenopausal breast cancer risk. This combined effect was stronger among women aged 60 years or older. However, the HRs were not significant in premenopausal women.

Conclusions

Our findings support the hypothesis that weight gain and consequent overweight/obesity are combined risk factors for breast cancer among postmenopausal women, particularly those aged 60 years or older.Key words: breast cancer, obesity, weight gain, cohort study     

Peer Reviewed: The Association Between Body Mass Index and Arthritis Among US Adults: CDC’s Surveillance Case Definition

Introduction

The Centers for Disease Control and Prevention modified the surveillance case definition of arthritis to a more stringent form in 2002. To date, the association between arthritis and obesity (an established risk factor for arthritis) has not been examined with the new definition. We describe the association between body mass index (BMI) (kg/m²) and arthritis using the new arthritis case definition to provide a more accurate assessment of the relationship between weight and arthritis among US adults.

Methods

We used data from the 2005 Behavioral Risk Factor Surveillance System (N = 356,112) and univariate and multivariate analyses to assess the relationship between BMI and arthritis among US adults.

Results

Overall, 26% of US adults had self-reported arthritis. Obese respondents (BMI ≥30.0 kg/m²) were 1.9 times more likely to report arthritis compared with normal-weight respondents (BMI <25.0 kg/m²), and distinguishing between obese levels revealed an even greater association between BMI and arthritis (class III obesity [BMI ≥40.0], odds ratio [OR] = 3.3, 95% confidence interval [CI] = 3.1-3.6; class II obesity [BMI 35.0-39.9 kg/m²], OR = 2.5, 95% CI = 2.3-2.7; class I obesity [BMI 30.0-34.9], OR = 1.9, 95% CI = 1.8-2.0).

Conclusion

BMI is an independent risk factor for self-reported arthritis. Maintaining a healthy weight may delay the onset of arthritis. More research is needed to determine the effect of weight loss on the progression of arthritis in overweight individuals.     

Prenatal organochlorine compound exposure, rapid weight gain, and overweight in infancy

Background

Although it has been hypothesized that fetal exposure to endocrine-disrupting chemicals may increase obesity risk, empirical data are limited, and it is uncertain how early in life any effects may begin.

Objectives

We explored whether prenatal exposure to several organochlorine compounds (OCs) is associated with rapid growth in the first 6 months of life and body mass index (BMI) later in infancy.

Methods

Data come from the INMA (Infancia y Medio-Ambiente) Child and Environment birth cohort in Spain, which recruited 657 women in early pregnancy. Rapid growth during the first 6 months was defined as a change in weight-for-age z-scores > 0.67, and elevated BMI at 14 months, as a z-score ≥ the 85th percentile. Generalized linear models were used to estimate the risk of rapid growth or elevated BMI associated with 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene (DDE), hexachlorobenzene, β-hexachlorohexane, and polychlorinated biphenyls in first-trimester maternal serum.

Results

After multivariable adjustment including other OCs, DDE exposure above the first quartile was associated with doubling of the risk of rapid growth among children of normal-weight (BMI < 25 kg/m²), but not overweight, mothers. DDE was also associated with elevated BMI at 14 months (relative risk per unit increase in log DDE = 1.50; 95% confidence interval, 1.11–2.03). Other OCs were not associated with rapid growth or elevated BMI after adjustment.

Conclusions

In this study we found prenatal DDE exposure to be associated with rapid weight gain in the first 6 months and elevated BMI later in infancy, among infants of normal-weight mothers. More research exploring the potential role of chemical exposures in early-onset obesity is needed.     

Primary school compliance with school canteen guidelines in Fiji and its association with student obesity

Setting:

Childhood obesity is of growing public health concern in Fiji. The study setting was primary schools in Fiji’s Western Division.

Objective:

1) To assess primary schools’ compliance with national school canteen guidelines, 2) to understand reasons for non-compliance, and 3) to assess the relationship between compliance with the guidelines and students’ body mass index (BMI).

Design:

Cross-sectional analysis of data collected in 2010 by public health dieticians of the Ministry of Health on annual visits to primary schools.

Results:

Among 230 schools, 33 (14%) had no canteen data. Of the 197 schools with data, only 31 (16%) were fully compliant with national school canteen guidelines, while the remaining 166 (84%) did not fully comply with the guidelines. This was irrespective of school location or whether the canteen was school or commercially operated. In a random sample (n = 44 schools), overweight and obesity were more common among children in non-compliant schools than in fully compliant schools (40% vs. 32%, P < 0.001).

Conclusion:

Most primary schools in Fiji’s Western Division did not comply with school canteen guidelines, which is worrying given the increasing rates of overweight children. Given the association between non-compliance and student overweight/obesity, further action is needed to ensure that these guidelines are implemented.     

Associations Between Polymorphisms in the Glucocorticoid-Receptor Gene and Cardiovascular Risk Factors in a Chinese Population

Background

Glucocorticoid is an important regulator of energy homeostasis. Glucocorticoid receptor (GR) gene polymorphisms that contribute to variability in glucocorticoid sensitivity have been identified. We explored the associations of single-nucleotide polymorphisms (SNPs) of the GR gene with traditional cardiovascular risk factors in the Chinese Han population.

Methods

We recruited 762 consecutive adults who underwent a regular physical examination at Beijing Xuanwu Hospital. Blood pressure, glucose, lipid levels (total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein [LDL] cholesterol and triglycerides), body mass index (BMI), and waist-to-hip ratio were measured. Fourteen tag SNPs and 5 functional SNPs were selected and genotyped using the high-throughput Sequenom genotyping platform. Differences between genotypes/alleles for each SNP were adjusted for sex and age and tested using a general linear model procedure. Various models of inheritance, including additive, dominant, and recessive, were tested.

Results

Among the 19 SNPs examined, 5 markers were associated with cardiovascular risk factors. The rs41423247 GG genotype and the rs7701443 AA genotype were associated with higher BMI and systolic blood pressure (P < 0.0004), and the rs17209251 GG genotype was associated with higher systolic blood pressure (P < 0.0004). Lower systolic blood pressure, total cholesterol, and LDL cholesterol were observed among rs10052957 A allele carriers (P < 0.0004), and lower plasma glucose and LDL-cholesterol concentrations were observed among rs2963156 TT carriers (P < 0.0004).

Conclusions

Polymorphism of the GR gene was associated with cardiovascular risk factors and may contribute to susceptibility to cardiovascular disease.Key words: glucocorticoid receptor gene, polymorphism, cardiovascular disease, risk factor     

Smoking cessation and body weight: evidence from the Behavioral Risk Factor Surveillance Survey

Objective

To investigate the role of smoking cessation in body weight.

Data Sources

2004–2005 and 2009–2010 Behavioral Risk Factor Surveillance Surveys (BRFSS) (N = 349,000), Centers for Disease Control and Prevention; Tax Burden on Tobacco (Orzechowski and Walker 2010).

Study Design

The Gaussian treatment effect model is estimated for three age categories by gender. Treatment effects of quitting smoking on body mass index (BMI) by quit length are calculated.

Principal Findings

Quitting is found to be endogenous. Differentiated effects of quitting smoking on BMI are found among quitters by gender, between age groups, and by length of time since quitting smoking, and positive association between smoking cessation and body weight confirmed. Declining smoking rates have only a modest effect in the overweight population. The effects of quitting on BMI are considerably lower among younger men and women.

Conclusion

The price that must be paid, in terms of weight gain, to enjoy the health benefits of smoking cessation is trivial even for the obese population.     

Peer Reviewed: Family Structure and Childhood Obesity,Early Childhood Longitudinal Study — Kindergarten Cohort

Introduction

Little is known about the effect of family structure on childhood obesity among US children. This study examines the effect of number of parents and number of siblings on children''s body mass index and risk of obesity.

Methods

We conducted a secondary data analysis of the Early Childhood Longitudinal Study — Kindergarten Cohort (ECLS-K), which consists of a nationally representative cohort of children who entered kindergarten during 1998-1999. Our analyses included 2 cross-sectional outcomes and 1 longitudinal outcome: body mass index (BMI) calculated from measured height and weight, obesity defined as BMI in the 95th percentile or higher for age and sex, and change in BMI from kindergarten through fifth grade.

Results

Other things being equal, children living with single mothers were more likely to be obese by fifth grade than were children living with 2 parents (26% vs 22%, P = .05). Children with siblings had lower BMI and were less likely to be obese than children without siblings. We also found that living with a single mother or no siblings was associated with larger increases in BMI from kindergarten through fifth grade.

Conclusion

Children from single-mother families and, especially, children with no siblings are at higher risk for obesity than children living with 2 parents and children with siblings. These findings highlight the influential role that families play in childhood obesity. Additionally, they suggest that health care providers should consider the structure of children''s families in discussions with families regarding childhood obesity.     

Peer Reviewed: Prevalence of Overweight and Influence of Out-of-School Seasonal Periods on Body Mass Index Among American Indian Schoolchildren

Introduction

The prevalence of overweight and obesity among American Indian youth may be 2 to 3 times higher than the national average. Whether weight gain during discrete out-of-school periods is occurring and contributing to the prevalence of overweight and obesity in this population is unknown.

Methods

We obtained repeated cross-sectional body mass index (BMI) samples from third-, fourth-, fifth-, seventh-, and eighth-grade boys and girls who reside on the Wind River Indian Reservation in central Wyoming. We collected measures at the beginning of 2 school years (N = 251), during 2 holiday breaks (N = 226), and during 1 summer recess (N = 141). We determined prevalence of normal weight and overweight among participants by grade level, and we calculated paired comparisons of BMI, BMI z score, and weight status during the holiday breaks and summer recess.

Results

Combined prevalence of at risk for overweight and overweight was 62.0% for boys and 56.6% for girls. For fifth-grade girls, significant increases in BMI (P = .01) and z score (P < .001) occurred over the holiday break. BMI increased significantly over the summer among third- and fifth-grade girls and among fourth-grade boys, but changes in z scores were nonsignificant. We observed an increase in weight status by out-of-school time in BMI (P < .001) for schoolchildren at or above the 85th BMI percentile over the summer recess, but corresponding z scores did not change.

Conclusion

Prevalence of overweight among American Indian schoolchildren was higher than national estimates and higher than the prevalence in other similarly aged American Indian youth. Increases in BMI during out-of-school periods are likely due to normal growth, except among fifth-grade girls.     

Relationship between adhering to dietary guidelines and the risk of obesity in Korean children

BACKGROUND/OBJECTIVES

Dietary guidelines for Korean children were released in 2009. The goal of the present study was to examine diet quality in terms of adherence to these dietary guidelines as well as explore the association between guideline adherence and risk of obesity in Korean children.

SUBJECTS/METHODS

Children aged 5-11 years (mean age = 8.9 years old, n = 191, 80.6% girls) were recruited from a university hospital in Seoul, Korea. Adherence to dietary guidelines for Korean children was calculated using the Likert scale (1-5), and children were then categorized into low, moderate, and high groups based on adherence scores. Obesity or being overweight was determined based on an age- and gender- specific percentile for body mass index (BMI) of the 2007 Korean National Growth Charts. Diet quality was evaluated from 3 days of dietary intake data.

RESULTS

Children in the high adherence group were characterized by significantly lower BMI percentiles and paternal BMIs as well as higher percentages of fathers with a high level of education and higher household incomes compared to those in the low or moderate group. Children in the high adherence group consumed significantly higher amounts of milk and dairy products, were less likely to consume lower than the EAR of phosphorus and iron, and had higher NARs for calcium, phosphorus, iron, zinc, and MAR than those in low groups. The ORs for obesity (BMI ≥ 95^th percentile) or being overweight including obesity (BMI ≥ 85^th percentile) were significantly lower in the high adherence group compared to the low adherence group (OR: 0.33, 95% CI = 0.13-0.82, P for trend = 0.019; OR: 0.26, 95% CI: 0.11-0.61 P for trend = 0.002).

CONCLUSIONS

Korean children who adhered to dietary guidelines displayed better diet quality and a reduced risk of obesity.     

Sleep Duration and Weight Gain: Reconsideration by Panel Data Analysis

Background

Inconsistent findings in previous studies of the association between sleep duration and changes in body mass index (BMI) may be attributed to misclassification of sleep duration fluctuations over time and unmeasured confounders such as genetic factors. The aim of the present study was to overcome these failings by using repeated measurements and panel data analysis to examine the sleep-BMI association.

Methods

Panel data were derived by secondary use of the data from mandatory health checkups at a Japanese gas company. Male non-shift workers aged 19–39 years in 2007 were annually followed until 2010 (n = 1687, 6748 records). BMI was objectively measured, and sleep duration was self-reported.

Results

Compared with 7-hour sleepers, panel analysis with the population-averaged model showed a significant increase in BMI among 5-hour (0.11 kg/m², P = 0.001), 6-hour (0.07 kg/m², P = 0.038), and ≥8-hour (0.19 kg/m², P = 0.009) sleepers. On the other hand, after adjustment for unobserved time-invariant confounders using the fixed-effects model, the magnitude of the association was considerably attenuated and no longer significant (5-hour, 0.07 kg/m², P = 0.168; 6-hour, 0.02 kg/m², P = 0.631; ≥8-hour sleepers, 0.06 kg/m², P = 0.460).

Conclusions

The longitudinal association between sleep duration and changes in BMI may be upwardly biased by unobserved time-invariant confounders rather than misclassified sleep duration. The net effect of sleep duration on weight gain may therefore be less than previously believed.Key words: longitudinal studies, sleep, obesity, weight gain, panel analysis     

Effect of the PPARG2 Pro12Ala Polymorphism and Clinical Risk Factors for Diabetes Mellitus on HbA1c in the Japanese General Population

Background

Although the peroxisome proliferator-activated receptor-γ2 (PPARG2) Pro12Ala gene variant is associated with diabetes mellitus, the associations and interactions of this polymorphism and known clinical risk factors with glycated hemoglobin (HbA1c) remain poorly understood. We investigated if carrying the Ala allele was inversely associated with HbA1c level and examined possible interactions.

Methods

This cross-sectional analysis used data collected from 1281 men and 1356 women aged 40 to 69 years who completed the baseline survey of the Japan Multi-Institutional Collaborative Cohort Study. PPARG2 polymorphism was determined by multiplex polymerase chain reaction (PCR)-based Invader assay. Multiple linear regression and ANCOVA were used to control for confounding variables (age, body mass index [BMI], energy intake, alcohol, smoking, physical activity, and family history of diabetes) and examine possible interactions.

Results

After adjustment, the Ala allele was significantly inversely associated with HbA1c in women but not in men. Older age, BMI, and family history of diabetes were associated with higher HbA1c in both sexes. When stratified by PPARG2 genotype, these associations were observed in subjects with the Pro12Pro genotype but not in Ala allele carriers. A significant interaction of genotype and BMI on HbA1c was observed in women. Older age, BMI, and family history of diabetes were significantly associated with high-normal HbA1c (≥5.7% NGSP), whereas PPARG2 polymorphism was not.

Conclusions

Although PPARG2 Pro12Ala polymorphism might attenuate associations between known risk factors and HbA1c level, it had a small effect on high-normal HbA1c, as compared with clinical risk factors, in the general population.Key words: peroxisome proliferator-activated receptor-γ2, polymorphism, glycated hemoglobin, interaction     

A 4-Year Study of the Association between Short Sleep Duration and Change in Body Mass Index in Japanese Male Workers

Background

Studies of Western populations have shown an inconsistent longitudinal association between short sleep duration and change in body mass index (BMI); a recent Japanese cohort study reported a significant association in men, but over a 1-year period. The aim of this longitudinal study was to examine whether this association was robust over a 4-year interval in Japanese men.

Methods

A total of 3803 middle-aged Japanese male white-collar workers (mean age 47.8 years, mean BMI 23.9 kg/m²) in Tokyo, Japan, were included in this study from 1994–1995 (baseline) to 1998–1999 (follow-up). Height and weight were objectively measured at annual health checkups, and other data, including sleep duration, were collected using a structured interview. We used linear regression models to estimate change in BMI, after adjustment for covariates. The reference category for sleep duration was set to 7 hours, to conform with previous studies.

Results

As compared with participants sleeping 7 hours, those sleeping 5 hours or less had a significantly higher BMI at baseline (beta coefficient: 0.34 kg/m², 95% confidence interval (CI): 0.03, 0.65) and gained 0.15 kg/m² in BMI over 4 years (95% CI: 0.03, 0.27), after adjustment for age, baseline BMI, lifestyle behavior, and medication.

Conclusions

The longitudinal association between short sleep duration at baseline and relative increase in BMI was significant in Japanese male workers over a 4-year interval.Key words: Japanese, longitudinal studies, obesity, sleep, weight gain