Journal of Epidemiology Vol. 27(2017) No. 9

Background: The associations of occupational activity (OA), commuting, leisure-time physical activity (LTPA), and sitting with overweight/obesity in working adults are controversial. This study explored these factors with the risk of overall and abdominal overweight/obesity in a Chinese working population and whether these associations differ by gender.

Methods: A cross-sectional study was conducted. Data analysis was done among 6739 employed participants. Multivariate logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) for the studied associations.

Results: For male employees, those with heavy OA had a lower overall (OR 0.76; 95% CI, 0.62–0.93) and abdominal (OR 0.76; 95% CI, 0.62–0.93) overweight/obesity risk than those with light OA. Those with LTPA ≥150 min/week had a lower risk of overall (OR 0.73; 95% CI, 0.56–0.96) and abdominal (OR 0.70; 95% CI, 0.53–0.91) overweight/obesity than those with LTPA <150 min/week. Men with leisure-sitting time <2.5 h/day had a significantly lower risk of abdominal overweight/obesity than those sitting ≥4 h/day (OR 0.80; 95% CI, 0.65–0.99). And men who cycled to/from work had a lower risk of overall (OR 0.69; 95% CI, 0.53–0.90) and abdominal overweight/obesity (OR 0.71; 95% CI, 0.54–0.92) than passive transports. However, the above significant associations disappeared among female employees.

Conclusions: Heavy OA, cycling to/from work, and LTPA were associated with lower risk of overall or abdominal overweight/obesity in male employees. Reducing leisure sitting time can also help male employees reduce the risk of abdominal overweight/obesity. More research on gender disparity in the risk of overweight and obesity should be done.

Background: We prospectively examined the association of diabetes risk with the number of metabolic abnormalities, as well as their combinations, according to the presence or absence of impaired fasting glucose (IFG) in a large-scale Japanese working population.

Methods: Participants included 55,271 workers at 11 companies who received periodic health check-ups between 2008 and 2013. The metabolic syndrome (MetS) components were defined using the 2009 Joint Interim Statement. IFG was defined as fasting plasma glucose 5.6–6.9 mmol/L. Diabetes newly diagnosed after the baseline examination was defined according to the American Diabetes Association criteria. We calculated the hazard ratios (HRs) for diabetes incidence using the Cox proportional hazards model.

Results: During the follow-up period (median 4.95 years), 3183 subjects developed diabetes. In individuals with normal fasting glucose levels, the risk of diabetes increased steadily with the increasing number of MetS components; the multivariable-adjusted HRs for incident diabetes for the number of MetS components were 2.0, 4.3, 7.0, and 10.0 for one, two, three, or four MetS components, respectively, compared with the absence of components. A similar association was observed among individuals with IFG; the corresponding HRs were 17.6, 23.8, 33.9, and 40.7. The combinations that included central obesity appeared to be more strongly associated with diabetes risk than other combinations with the same number of MetS components within the same glucose status.

Conclusions: Our findings indicate that risk stratification of individuals by the presence or absence of IFG and the number of MetS components can detect individuals with a high risk of diabetes.

Background: Recent obesity studies have reported that the rising trend in obesity has stabilized or leveled off. Our study aimed to update estimates of the recent prevalence trend in obesity based on the Korean National Health and Nutrition Examination Survey 1998–2014.

Methods: A total of 66,663 subjects were included and defined as being either underweight, overweight, or obese, in accordance with a BMI of 18.5 kg/m² or lower, 23 kg/m² or higher, and 25 kg/m² or higher, respectively.

Results: The prevalence of underweight in KNHANES I through VI surveys was 5.4%, 6.1%, 5.8%, 6.5%, 7.6%, and 7.5%, respectively, in men (p for trend = 0.04, β = 0.003) and 4.7%, 3.3%, 3.4%, 3.3%, 2.7%, and 2.6%, respectively, in women (p for trend = 0.03, β = −0.002). Also for KNHANES I through VI, the respective prevalence of overweight/obesity was 50.3%, 57.2%, 62.5%, 62.3%, 61.4%, and 61.3% in men (p for trend<0.01, β = 0.009) and 48.3%, 50.3%, 50.0%, 47.8%, 47.0%, and 45.3% in women (p for trend<0.01, β = −0.01), respectively.

Conclusions: The obesity occurrence in men was trending upward with respect to overweight/obesity and for grade 1 and 2 obesity, but not for abdominal obesity. However, the obesity trends in women were leveling off from overweight/obesity, grade 1 obesity, and abdominal obesity measures. Further studies are required with data on muscle mass and adiposity for effective obesity control policies.

Background: An increased risk of total death owing to human T-lymphotropic virus type-I (HTLV-I) infection has been reported. However, its etiology and protective factors are unclear. Various studies reported fluctuations in immune-inflammatory status among HTLV-I carriers. We conducted a matched cohort study among the general population in an HTLV-I-endemic region of Japan to investigate the interaction between inflammatory gene polymorphisms and HTLV-I infection for total death, incidence of cancer, and atherosclerosis-related diseases.

Method: We selected 2180 sub-cohort subjects aged 35–69 years from the cohort population, after matching for age, sex, and region with HTLV-I seropositives. They were followed up for a maximum of 10 years. Inflammatory gene polymorphisms were selected from TNF-α, IL-10, and NF-κB1. A Cox proportional hazard model was used to estimate the hazard ratio (HR) and the interaction between gene polymorphisms and HTLV-I for risk of total death and incidence of cancer and atherosclerosis-related diseases.

Results: HTLV-I seropositivity rate was 6.4% in the cohort population. The interaction between TNF-α 1031T/C and HTLV-I for atherosclerosis-related disease incidence was statistically significant (p = 0.020). No significant interaction was observed between IL-10 819T/C or NF-κB1 94ATTG ins/del and HTLV-I. An increased HR for total death was observed in the Amami island region, after adjustment of various factors with gene polymorphisms (HR 3.03; 95% confidence interval, 1.18–7.77).

Conclusion: The present study found the interaction between TNF-α 1031T/C and HTLV-I to be a risk factor for atherosclerosis-related disease. Further follow-up is warranted to investigate protective factors against developing diseases among susceptible HTLV-I carriers.

Background: Although birth weight is considered as a fetal determinant of the development of adult-onset diabetes mellitus (DM), its public health importance relative to adult body mass index (BMI) remains unclear. We aimed to examine the association between adult-onset DM and birth weight in relation to adult BMI.

Methods: We conducted a self-administered questionnaire as a baseline survey of the Japanese Nurses' Health Study cohort between 2001 and 2007. Exclusion criteria were applied to the volunteer sample of 49,927 female nurses (age <30 years or unknown, current pregnancy, development of DM before the age of 30 years, unknown core variables), and data from 26,949 female nurses aged 30 years or older were used. The association between history of DM diagnosis and birth weight was analyzed using logistic regression.

Results: A linear inverse association was observed between birth weight and DM, after adjustment for age, BMI, and parental history of DM. The odds ratio for developing DM per 100 g increase in birth weight was 0.93 (95% confidence interval [CI], 0.90–0.96). The association was unchanged when birth weight was converted to percentile for gestational age. In the BMI-stratified analysis, the odds ratio for DM in the <2500 g birth weight group reached 4.75 (95% CI, 1.22–18.44, compared to the reference 3000–3499 g group) among women with normal low BMI (18.5–20.9).

Conclusions: Birth weight and its percentile for gestational age were associated with adult-onset DM. Attention should be paid to the risk of DM among women born with low weight, even when their current BMI is normal.

Background: Online dietary assessment tools offer advantages over printed questionnaires, such as the automatic and direct data storage of answers, and have the potential to become valuable research methods. We developed an online survey system (web-FFQ) for the existing printed FFQ used in the JPHC-NEXT protocol, the platform of a large-scale genetic cohort study. Here, we examined the validity of ranking individuals according to dietary intake using this web-FFQ and its usability compared with the printed questionnaire (print-FFQ) for combined usage.

Methods: We included 237 men and women aged 40–74 years from five areas specified in the JPHC-NEXT protocol. From 2012 to 2013, participants were asked to provide 12-day weighed food records (12d-WFR) as the reference intake and to respond to the print- and web-FFQs. Spearman's correlation coefficients (CCs) between estimates using the web-FFQ and 12d-WFR were calculated. Cross-classification of intakes was compared with those using the print-FFQ.

Results: Most participants (83%) answered that completing the web-FFQ was comparable to or easier than completing the printed questionnaire. The median value of CCs across energy and 53 nutrients for men and women was 0.47 (range, 0.10–0.86) and 0.46 (range, 0.16–0.69), respectively. CCs for individual nutrient intakes were closely similar to those based on the print-FFQ, irrespective of response location. Cross-classification by quintile of intake based on two FFQs was reasonably accurate for many nutrients and food groups.

Conclusion: This online survey system is a reasonably valid measure for ranking individuals by intake for many nutrients, like the printed FFQ. Mixing of two FFQs for exposure assessments in epidemiological studies appears acceptable.

Background: Leber hereditary optic neuropathy (LHON) is a maternally inherited optic neuropathy that leads to central loss of vision, predominantly in young males. Most LHON cases have one of three primary point mutations in mitochondrial DNA (mtDNA). The annual incidence and prevalence of LHON in Japan are not known. Thus, we estimated the annual incidence of molecularly confirmed LHON in Japan during 2014.

Methods: Sequential questionnaires were sent to 1397 facilities, which included all of the university hospitals in Japan, and they were certified by either the Japanese Ophthalmological Society or the Japanese Neuro-Ophthalmological Society. We calculated the incidence number (I_r) as the number of patients who developed LHON in 2014 and its 95% confidence interval.

Results: We received 861 responses to the first questionnaire, where 49 facilities reported 72 cases (67 were male and 5 were female) of newly developed LHON during 2014. I_r was calculated as 117, and the 95% confidence interval ranged from 81 to 153. For the second questionnaire, responses were received from 30 facilities, where the median age at onset was 38 years for males and 30 years for females, and 86.5% of cases possessed the mtDNA ND4/G11778A mutation.

Conclusion: Approximately 120 cases of newly developed LHON were reported during 2014 in Japan, and 93.2% were males.