The Association between Anthropometric Indices of Obesity and Chronic Kidney Disease in Middle-aged Japanese Men and Women: A Cohort Study.

Objective This study investigated associations between three indices of obesity-the body mass index (BMI), waist circumference (WC), and waist-to-height ratio (WHtR)-and the incidence of chronic kidney disease (CKD). Methods The employees of a company in Japan (1,725 men, 1,186 women; aged 35-55 years) had BMI, WC, and WHtR measured in health examinations. The incidence of CKD was determined at annual medical examinations over a six-year period. The hazard ratios for CKD were calculated using proportional hazard models, and the χ2 statistic was used to compare the strengths of the associations. Results The mean BMI (kg/m2), WC (cm), and WHtR were 23.6, 84.3, and 0.49 for men and 22.3, 79.7, and 0.50 for women, respectively. The incidence of CKD (/1,000 person-years) was 18.1 for men and 8.4 for women. In men, positive linear associations were observed between the BMI, WC, and WHtR and the risk of CKD, even after adjusting for the presence of metabolic abnormalities (p for trend <0.001, 0.012, and 0.023, respectively). In women, a linear association was observed only between the WHtR and CKD, not the BMI or WC (p for trend =0.042, 0.057, and 0.186). The χ2 statistics were the highest for the BMI in both men and women. Conclusion The BMI, WC, and WHtR were linearly associated with the risk of CKD independently of metabolic abnormalities in men, while the associations were weaker or not significant in women. The BMI was the most strongly associated with the incidence of CKD in both men and women.

Frequency of consumption of balanced meals, bodyweight gain and incident risk of glucose intolerance in Japanese men and women: A cohort study.

AIMS/INTRODUCTION: This cohort study assessed the risk for bodyweight gain and development of glucose intolerance based on the frequency of consumption of balanced meals including grain, fish or meat and vegetables. MATERIALS AND METHODS: The participants (8,573 men, 3,327 women) were employees of a company in Japan. A self-administered questionnaire was used to evaluate the frequency of balanced meal consumption. Bodyweight changes and the incidence of glucose intolerance (glycated hemoglobin >6.0%) during the 3-year follow-up period were determined through annual health examinations. RESULTS: The mean bodyweight change over a period of 3 years was 0.78 kg for men and 0.84 kg for women. A lower frequency of balanced meals was associated with a higher bodyweight gain for men (P for trend = 0.004), but not for women. During the study, 464 men and 115 women developed glucose intolerance. Overall, the frequency of balanced meals was not associated with the risk of glucose intolerance in either sex. However, the interaction between the frequency of balanced meals and degree of obesity had a significant effect on the incidence of glucose intolerance in men (P = 0.005), with less frequent consumption of balanced meals being associated with a higher risk for glucose intolerance among men with a BMI ≥25.0 kg/m2 (P for trend = 0.007). CONCLUSIONS: A higher frequency of balanced meals, including grain, fish or meat and vegetable dishes - important components of healthy Japanese food - was associated with a lower risk of glucose intolerance in obese men, but not in non-obese men and women.

Health status of workers approximately 60 years of age and the risk of early death after compulsory retirement: A cohort study.

OBJECTIVES: The increasing number of working elderly people has enhanced the importance of workplace health promotion activities. We investigated the association between the health status of workers approximately 60 years of age and the risk of all-cause mortality after compulsory retirement in Japan. METHODS: The 2026 participants (1299 males and 727 females) had retired from a metal-products factory at ≥60 years of age. Baseline health examinations were conducted at 60 years of age and included questions about medical history and lifestyle factors; the participants also underwent a physical examination. The participants were followed up annually by mail for an average of 7.4 years. The association between health status at age 60 years and the risk of all-cause mortality was assessed by Cox proportional hazards regression analysis. RESULTS: During the study, 71 deaths were reported. The age- and sex-adjusted hazard ratio (HR [95% confidence interval]) for all-cause mortality was higher for males (HR, 3.41 [1.73-6.69]) compared with females, participants with a low body mass index (<18.5 kg/m2 ; HR 3.84 [1.91-7.73]) compared with normal body weight, smokers (HR, 2.63 [1.51-4.58]) compared with nonsmokers, and those with three or more of four metabolic abnormalities (obesity, high blood pressure, dyslipidemia, and glucose intolerance) (HR 2.29 [1.04-5.02]) compared with no metabolic abnormalities. The associations were unaffected by adjustment for these factors. CONCLUSION: Maintenance of an appropriate body weight, smoking cessation, and elimination of metabolic syndrome are required for older workers to prevent early death after retirement.

Serum Ferritin, Insulin Resistance, and ß-cell Dysfunction: A Prospective Study in Normoglycemic Japanese Men.

Objectives: The present cohort study investigated the relationship between serum ferritin levels and indices of insulin resistance and ß-cell dysfunction in a normoglycemic population without iron overload disorders. Methods: The study participants included 575 normoglycemic Japanese men aged 35-57 years with serum ferritin levels of 400 µg/L or less. Insulin resistance and ß-cell dysfunction were estimated at baseline and after 3 years by the homeostasis model assessments of insulin resistance and ß-cell function (HOMA-IR and HOMA-ß, respectively). To compare the subsequent changes in HOMA-IR and HOMA-ß over a 3-year follow-up period among 3 groups based on tertiles of baseline serum ferritin levels (4.9-87.1, 87.2-140.5, and 140.6-396.8 µg/L), the geometric mean HOMA-IR and HOMA-ß values at year 3 were calculated for each group using analysis of covariance, incorporating the respective log-transformed parameters at baseline in addition to age, body mass index and major confounding factors. Results: The multivariate-adjusted geometric mean HOMA-IR at year 3 was significantly higher in those in the highest and middle serum ferritin tertiles (1.24 and 1.22, respectively), compared with the lowest tertile (1.07) (p=0.009). When the total study participants were stratified by median body mass index (22.72 kg/m2), similar positive relationships were observed between serum ferritin levels and HOMA-IR for both obese and non-obese participants. However, the adjusted geometric mean HOMA-ß at year 3 was similar among the 3 serum ferritin groups. Conclusions: Elevated serum ferritin levels predicted a subsequent increase in HOMA-IR in normoglycemic Japanese men without iron overload disorders.

A diagnostic marker for superficial urothelial bladder carcinoma: lack of nuclear ATBF1 (ZFHX3) by immunohistochemistry suggests malignant progression.

BACKGROUND: Pathological stage and grade have limited ability to predict the outcomes of superficial urothelial bladder carcinoma at initial transurethral resection (TUR). AT-motif binding factor 1 (ATBF1) is a tumor suppressive transcription factor that is normally localized to the nucleus but has been detected in the cytoplasm in several cancers. Here, we examined the diagnostic value of the intracellular localization of ATBF1 as a marker for the identification of high risk urothelial bladder carcinoma. METHODS: Seven anti-ATBF1 antibodies were generated to cover the entire ATBF1 sequence. Four human influenza hemagglutinin-derived amino acid sequence-tagged expression vectors with truncated ATBF1 cDNA were constructed to map the functional domains of nuclear localization signals (NLSs) with the consensus sequence KR[X10-12]K. A total of 117 samples from initial TUR of human bladder carcinomas were analyzed. None of the patients had received chemotherapy or radiotherapy before pathological evaluation. RESULTS: ATBF1 nuclear localization was regulated synergistically by three NLSs on ATBF1. The cytoplasmic fragments of ATBF1 lacked NLSs. Patients were divided into two groups according to positive nuclear staining of ATBF1, and significant differences in overall survival (P = 0.021) and intravesical recurrence-free survival (P = 0.013) were detected between ATBF1+ (n = 110) and ATBF1- (n = 7) cases. Multivariate analysis revealed that ATBF1 staining was an independent prognostic factor for intravesical recurrence-free survival after adjusting for cellular grading and pathological staging (P = 0.008). CONCLUSIONS: Cleavage of ATBF1 leads to the cytoplasmic localization of ATBF1 fragments and downregulates nuclear ATBF1. Alterations in the subcellular localization of ATBF1 due to fragmentation of the protein are related to the malignant character of urothelial carcinoma. Pathological evaluation using anti-ATBF1 antibodies enabled the identification of highly malignant cases that had been overlooked at initial TUR. Nuclear localization of ATBF1 indicates better prognosis of urothelial carcinoma.

Dietary carbohydrate intake, presence of obesity and the incident risk of type 2 diabetes in Japanese men.

AIMS/INTRODUCTION: The present cohort study assessed the risk among Japanese men for developing type 2 diabetes, based on the percentage of energy intake from carbohydrates and degree of obesity. PARTICIPANTS AND METHODS: The participants were 2,006 male factory employees, and the macronutrient intake of each patient was measured using a self-administered diet history questionnaire. The incidence of diabetes was determined in annual blood examinations over a 10-year period. RESULTS: During the study, 232 participants developed diabetes. The crude incidence rates (/1,000 person-years) for different levels of carbohydrate intake as a percentage of calories consumed (<50.0, 50.0-57.4, 57.5-65.0, >65.0% of energy intake) were 16.5, 14.4, 12.7 and 17.6. Overall, carbohydrate intake was not associated with the risk of diabetes. However, there was significant interaction between carbohydrate intake and degree of obesity on the incidence of diabetes (P for interaction = 0.024). Higher carbohydrate intake was associated with elevated risk for diabetes among participants with a body mass index ≥25.0 kg/m(2) (P for trend = 0.034). For obese participants, the multivariate-adjusted hazard ratio for those with carbohydrate intakes >65% energy was 2.01 (95% confidence interval 1.08-3.71), which was significantly higher than that of participants with carbohydrate intakes 50.0-57.4% energy. CONCLUSIONS: Higher carbohydrate intake was associated with higher risk of diabetes in obese participants, but not in non-obese participants. Obese participants with carbohydrate intakes >65% energy should reduce their intakes to levels within the desirable carbohydrate energy proportion for Japanese (50-65% energy) to prevent development of type 2 diabetes.

Relationship of Consumption of Meals Including Grain, Fish and Meat, and Vegetable Dishes to the Prevention of Nutrient Deficiency: The INTERMAP Toyama Study.

A Japanese-style diet consists of meals that include grain (shushoku), fish and meat (shusai), and vegetable dishes (fukusai). Little is known about the association of such meals (designated well-balanced meals hereafter) with nutrient intake. We therefore examined the frequency of well-balanced meals required to prevent nutrient deficiency. Participants were Japanese people, ages 40 to 59 y, from Toyama, recruited for INTERMAP, in an international population-based study. Each person provided 4 in-depth 24-h dietary recalls (149 men, 150 women). The prevalence of risk ratios of not meeting the Dietary Reference Intakes for Japanese (2015) was calculated. Well-balanced diets were assessed by the Japanese Food Guide Spinning Top. We counted the frequencies of meals in which participants consumed 1.0 or more servings of all 3 dishes categories. We divided the frequency of consumption of well-balanced meals into the following 4 groups: <1.00 time/d, 1.00-1.49 times/d, 1.50-1.74 times/d, and ≥1.75 times/d. Compared with participants in the highest frequency group for well-balanced meals, those who consumed well-balanced meals less than once a day had a higher risk of not meeting the adequate intake for potassium and the recommended dietary allowance for vitamin A. Those who consumed well-balanced meals on average less than 1.50 times per day had a higher risk of not meeting the recommended dietary allowance for calcium and vitamin C. Our results suggest that individuals should on average consume well-balanced meals more than 1.5 times per day to prevent calcium and vitamin C deficiencies.

Overall sleep status and high sensitivity C-reactive protein: a prospective study in Japanese factory workers.

We investigated the relation between overall sleep status based on the modified Pittsburgh Sleep Quality Index (PSQI) global score and subsequent changes in serum high-sensitivity C-reactive protein (hsCRP) in a population of Japanese factory workers, who were predominantly female. A total of 991 Japanese with inflammation classified as low cardiovascular risk (baseline hsCRP < 1.0 mg L(-1) ) were grouped according to the presence or absence of unfavourable sleep, defined as a modified PSQI global score > 5.5 points. The subsequent changes in hsCRP after 3 years were then compared in the two groups. Analysis of covariance incorporating log-transformed baseline hsCRP, age, sex, lifestyle and physical and biochemical profiles was used to compare the geometric means of hsCRP at year 3 in each sleep status group. A logistic regression model incorporating the same variables was used to calculate the odds ratios for development of inflammation with a medium-to-high cardiovascular risk (hsCRP at year 3 ≥ 1.0 mg L(-1) ) comparing the presence or absence of unfavourable sleep habits. The multivariate-adjusted geometric mean of hsCRP at year 3 was significantly higher in subjects with unfavourable sleep habits compared with those with a normal pattern (0.275 versus 0.242 mg L(-1) ). The multivariate-adjusted odds ratio for developing increased and potentially pathogenic levels of inflammation due to unfavourable sleep was 2.08 (95% confidence interval = 1.29-3.35). There was a significant linear trend for the development of increased inflammation across the modified PSQI global scores (P = 0.04). Unfavourable sleep is associated with activation of low-grade systemic inflammation.

Associations between rice, noodle, and bread intake and sleep quality in Japanese men and women.

BACKGROUND: Previous studies have shown that a diet with a high-glycemic index is associated with good sleep quality. Therefore, we investigated the association of sleep quality with the intake of 3 common starchy foods with different glycemic indexes-rice, bread, and noodles-as well as the dietary glycemic index in a Japanese population. METHODS: The participants were 1,848 men and women between 20 and 60 years of age. Rice, bread, and noodle consumption was evaluated using a self-administered diet history questionnaire. Sleep quality was evaluated by using the Japanese version of the Pittsburgh Sleep Quality Index, and a global score >5.5 was considered to indicate poor sleep. RESULTS: Multivariate-adjusted odds ratios (95% confidence intervals) for poor sleep across the quintiles of rice consumption were 1.00 (reference), 0.68 (0.49-0.93), 0.61 (0.43-0.85), 0.59 (0.42-0.85), and 0.54 (0.37-0.81) (p for trend = 0.015); those for the quintiles of noodle consumption were 1.00 (reference), 1.25 (0.90-1.74), 1.05 (0.75-1.47), 1.31 (0.94-1.82), and 1.82 (1.31-2.51) (p for trend = 0.002). Bread intake was not associated with sleep quality. A higher dietary glycemic index was significantly associated with a lower risk of poor sleep (p for trend = 0.020). CONCLUSION: A high dietary glycemic index and high rice consumption are significantly associated with good sleep in Japanese men and women, whereas bread intake is not associated with sleep quality and noodle consumption is associated with poor sleep. The different associations of these starchy foods with sleep quality might be attributable to the different glycemic index of each food.

HOMA-IR and the risk of hyperuricemia: a prospective study in non-diabetic Japanese men.

AIMS: To examine the relation of insulin resistant status determined by homeostasis model assessment of insulin resistance (HOMA-IR) with the risk of incident hyperuricemia. METHODS: The study participants included 2071 Japanese men without hyperuricemia and diabetes, aged 35-54 years. The participants had undergone annual heath examinations for 6 years to compare incident hyperuricemia (serum uric acid >416.4µmol/L (7.0mg/dL) and/or taking medication for hyperuricemia) in four groups based on quartiles of baseline HOMA-IR. RESULTS: During follow-up there were 331 incident cases of hyperuricemia. The hazard ratios for hyperuricemia, compared with HOMA-IR ≤0.66, were 1.42 (95% confidence interval 1.02-1.98) for HOMA-IR 0.67-0.98, 1.20 (0.86-1.68) for HOMA-IR 0.99-1.49 and 1.44 (1.04-1.98) for HOMA-IR ≥1.50 after adjustment for baseline serum uric acid, creatinine, hypercholesterolemia and hypertension status, age, alcohol intake, and smoking and exercise habits. The hazard ratio associated with an increase of one standard deviation in lnHOMA-IR (1.85 as one geometric standard deviation of HOMA-IR) was 1.14 (1.03-1.28) (p for trend=0.02). CONCLUSIONS: Increased HOMA-IR independently predicted the subsequent development of hyperuricemia. Insulin resistance itself or compensatory hyperinsulinemia may contribute to the development of hyperuricemia.

Association between a serum thyroid-stimulating hormone concentration within the normal range and indices of obesity in Japanese men and women.

OBJECTIVE: This cross-sectional study investigated the associations between the serum thyroid-stimulating hormone (TSH) concentration and indices of obesity in middle-aged Japanese men and women. METHODS: The participants were 2,037 employees (1,044 men and 993 women; age, 36-55 yr) of a metal products factory in Japan. Clinical examinations were conducted in 2009. We obtained a medical history and anthropometric measurements (body weight, body mass index [BMI] and waist circumference) and measured the serum TSH concentrations. The anthropometric indices were compared across serum TSH quartiles. The associations were evaluated separately according to the smoking status in men. RESULTS: The mean body weight (kg), BMI (kg/m(2)) and waist circumference (cm) were 69.2, 23.7 and 83.2 in men and 55.3, 22.3 and 74.3 in women, respectively. Men with a higher TSH concentration had higher body weight and BMI values (p for trend=0.016 and 0.019, respectively), and these significant associations were observed even after adjusting for age, smoking status and other potential confounders. The TSH level was not associated with waist circumference. We found a significant interaction between the TSH level and the smoking status on body weight (p for interaction=0.013) and a significant association between the TSH level and body weight in nonsmokers, but not in current smokers. No significant associations were observed between the TSH level and the anthropometric indices in women. CONCLUSION: Significant positive associations between the serum TSH concentration, body weight and BMI were detected in men only, and an interaction with the smoking status was observed for this association.

The effect of age on the relationships between work-related factors and heavy drinking.

AIMS: The aim of this study was to investigate age-related differences in the relationship between work-related factors and heavy drinking. METHODS: This study in 3,398 male workers at a factory in Japan examined data on heavy drinking, defined as an alcohol consumption >40 g/day, and work-related factors including occupation, shift work, and job stress evaluated using the Japanese version of the Karasek's Job Content Questionnaire (JCQ). In the present cross-sectional study, alcohol consumption was assessed using a self-administered diet history questionnaire (DHQ). RESULTS: The prevalence of heavy drinkers in the study population was 15.5% and rose with increasing age. An increase in the odds ratio (OR) for heavy drinking was observed consistently in blue-collar workers compared with white-collar workers in all age groups. In subjects aged 20-29 years, shift work had also increased the OR for heavy drinking. In subjects aged 40-49 years, the two groups with a lower decision latitude had an increased OR compared with the highest group. In subjects aged 20-29 years, the age adjusted OR for individuals who received the lowest level of social support in the workplace was increased significantly compared with the highest group (4.22 [95%CI, 1.07-16.62] ). On the other hand, social support showed a positive association with heavy drinking in subjects aged 40-49 and 50-59 years. Job demand was not related to heavy drinking in any of the age groups. CONCLUSIONS: Our findings suggest that occupation and work schedule are related to alcohol use more apparently in a younger age group and that psychosocial factors are related to enhancement or prevention of alcohol use.

Nicotine dependence and cost-effectiveness of individualized support for smoking cessation: evidence from practice at a worksite in Japan.

Given the lack of economic studies evaluating the outcomes of smoking cessation programs from the viewpoint of program sponsors, we conducted a case study to provide relevant information for worksites. The present study was carried out between 2006 and 2008 at a manufacturing factory in the Toyama Prefecture of Japan and included subjects who voluntarily entered a smoking cessation program. The program included face-to-face counselling followed by weekly contact to provide encouragement over six months using e-mail or inter-office mail. Nicotine patches were available if required. All 151 participants stopped smoking immediately. Over the 24-month study period, self-report showed 49.7% abstained continuously from smoking. The rate of 24-month consecutive abstinence was higher in participants with lower Fagerström Test scores for Nicotine Dependence at baseline than in those with higher scores (63.6% for 0-2 points vs. 46.5% for 3-6 points vs. 43.8% for 7-10 points; chi-square test p = 0.19). A logistic regression model showed a significant linear trend for the association between the score and abstinence status after adjustment for possible confounding factors (p = 0.03). The crude incremental cost for one individual to successfully quit smoking due to the support program was ¥46,379 (i.e., ¥100 = $1.28, £0.83, or €1.03 at foreign exchange rates). The corresponding costs for the three categories of the Fagerström Test score for Nicotine Dependence were ¥31,953, ¥47,450 and ¥64,956, respectively. When a sensitivity analysis was conducted based on the 95% confidence interval of the success rate, the variance in the corresponding costs was ¥25,514-45,034 for 0-2 points, ¥38,344-61,824 for 3-6 points, and ¥45,698-108,260 for 7-10 points. The degree of nicotine dependence may therefore be an important determinant of the cost-effectiveness of smoking cessation programs.

Correlation between shift-work-related sleep problems and heavy drinking in Japanese male factory workers.

AIMS: To investigate the effects of shift work on increased alcohol intake associated with poor sleep quality. METHODS: This cross-sectional survey evaluated the correlation between work schedule, poor sleep quality and heavy drinking among 909 factory workers aged 35-54 years in Japan. Subjects included 530 day workers, 72 shift workers who did not work at night and 290 shift workers who engaged in night work. Heavy drinking was defined as a mean volume of alcohol consumption exceeding 60 g/day. RESULTS: Compared with other workers, night-shift workers who suffered poor sleep quality exhibited the highest frequency of heavy drinking (17.6%). Multiple logistic regression analysis demonstrated that compared with day workers with good sleep, night-shift workers who experienced poor sleep had more than twice the odds of heavy alcohol consumption (odds ratio 2.17 [95% confidence interval (CI), 1.20-3.93]). Shift workers who did not work at night and day workers with poor sleep were not at increased odds of heavy drinking. CONCLUSION: Shift workers who engage in night work may try to modify their health behavior to cope with sleep problems. Such modification may be a risk factor for heavy drinking.

Family history of diabetes, lifestyle factors, and the 7-year incident risk of type 2 diabetes mellitus in middle-aged Japanese men and women.

AIMS/INTRODUCTION: This cohort study of middle-aged Japanese participants investigated the relationship between family history of diabetes, the incident risk of type 2 diabetes and the interaction of these variables with other factors. MATERIALS AND METHODS: Study participants were 3,517 employees (2,037 men and 1,480 women) of a metal products factory in Japan. Baseline health examinations included questions about medical history, physical examination, anthropometric measurements, questions about lifestyle factors, such as smoking, alcohol consumption and habitual exercise, and a self-administered diet history questionnaire. Family history of diabetes was defined as having at least one-first-degree relative with diabetes. The incidence of diabetes was determined in annual medical examinations over a 7-year period. Hazard ratios (HRs) for type 2 diabetes were estimated by Cox proportional hazards analysis. RESULTS: Of the 3,517 participants, 630 (18%) had a family history of diabetes mellitus. During the study, 228 participants developed diabetes. The age and sex-adjusted HR for type 2 diabetes in participants with a family history of diabetes was 1.82 (95% confidence interval 1.36-2.43) as compared with those without a family history of diabetes. HRs did not change after adjustment for body mass index and lifestyle factors. We found no interactions with body mass index, insulin resistance, pancreatic ß-cell function or lifestyle factors. CONCLUSIONS: Family history of diabetes was associated with the incident risk of diabetes, and these associations were independent of other risk factors, such as obesity, insulin resistance, and lifestyle factors in Japanese men and women.

Self-reported speed of eating and 7-year risk of type 2 diabetes mellitus in middle-aged Japanese men.

OBJECTIVE: This cohort study investigated the association between eating speed and the incidence of type 2 diabetes in middle-aged Japanese men. MATERIALS/METHODS: Participants were 2,050 male employees of a metal products factory in Japan. We measured self-reported categorical eating speed. The incidence of diabetes was determined in annual medical examinations over a 7-year period. The association between eating speed and the incidence of diabetes adjusted for multiple variables (age, family history of diabetes, smoking, alcohol drinking, habitual exercise, and presence of hypertension and hyperlipidemia) was evaluated using Cox proportional hazards models. RESULTS: The prevalence of obesity (BMI≥25 kg/m(2)) across the categories of eating speed (slow, medium, and fast) was 14.6, 23.3, and 34.8%, respectively, and a faster eating speed was associated with a higher prevalence of obesity. During the study, 177 participants developed diabetes. Crude incidence rates (/1,000 person-years) across the three categories of eating speed were 9.9, 15.6, and 17.3, respectively. Multivariate-adjusted hazard ratios (95% CI) across the categories were 1.00 (reference), 1.68 (0.93-3.02), and 1.97 (1.10-3.55), respectively, and eating speed was associated with the risk of diabetes (p for trend=0.030). After further adjustment for BMI, a significant association was not observed. CONCLUSIONS: Eating speed was associated with the incidence of diabetes. Since these associations were not significant after adjusting for BMI, eating speed may act via its effect on body weight. Eating speed is a controllable risk factor, and eating slowly could be an acceptable lifestyle intervention for the prevention of diabetes mellitus.

Overtime work and blood pressure in normotensive Japanese male workers.

BACKGROUND: Epidemiological studies have observed conflicting patterns as to whether overtime work increases blood pressure (BP), probably as a consequence of methodological issues. METHODS: We conducted a prospective cohort study to investigate the relationship between overtime work hours and 1-year changes in BP in 1,235 normotensive Japanese male workers who carried out a variety of jobs in a manufacturing factory. Casual BP measurements were repeated at annual health examinations in 2004-2005, using an automatic manometer. An analysis of covariance that incorporated potential confounding factors including baseline age, body mass index (BMI), and lifestyle factors was used to calculate and compare the means of the 1-year change in systolic (SBP) and diastolic BP (DBP). The participants were grouped according to their average monthly overtime work hours obtained from timecard data between April and September 2004. RESULTS: The multivariate-adjusted mean for 1-year change in DBP in 611 male assembly-line workers was 1.5 mm Hg (95% confidence interval (CI) 0.8-2.2) for <40.0 h/month, 2.3 mm Hg (95% CI 1.3-3.2) for 40.0-79.9 h/month, and 5.3 mm Hg (95% CI 2.7-7.9) for ≥ 80.0 h/month (P for heterogeneity = 0.02). A broadly similar pattern was observed for SBP. In contrast, there was no significant difference in means 1-year change for both SBP and DBP in 315 clerks and 309 engineers/special technicians, grouped according to overtime work hours. CONCLUSIONS: Extensive overtime work was associated with increased BP in normotensive male assembly-line workers, but not in clerks and engineers/special technicians.

Dietary glycemic index and risk of type 2 diabetes mellitus in middle-aged Japanese men.

This cohort study investigated the association between dietary glycemic index (GI), glycemic load (GL), and the incidence of type 2 diabetes mellitus in middle-aged Japanese men, and the effect of insulin resistance and pancreatic B-cell function on the association. Participants were 1995 male employees of a metal products factory in Japan. Dietary GI and GL were assessed using a self-administered diet history questionnaire. The incidence of diabetes was detected in annual medical examinations over a 6-year period. The association between GI, GL, and the incidence of diabetes was evaluated using Cox proportional hazards models. During the study, 133 participants developed diabetes. Age- and body mass index-adjusted hazard ratios across the GI quintiles were 1.00 (reference), 1.62, 1.50, 1.68, and 1.80; and those of GL were 1.00 (reference), 1.07, 1.48, 0.95, and 0.98. The hazard ratio for the highest GI quintile was significantly greater than that for the lowest quintile. The influence of GI was more pronounced in the lowest insulin resistance subgroups. GI and pancreatic B-cell function were independently associated with the incidence of type 2 diabetes mellitus; participants with low B-cell function and the highest tertile of GI had the highest risk of diabetes. Dietary GI is associated with the incidence of diabetes in middle-aged Japanese men. GI and B-cell function were independently associated with incidence of diabetes.

The effects of sleep duration on the incidence of cardiovascular events among middle-aged male workers in Japan.

OBJECTIVES: Although previous epidemiological studies have investigated the relationship between sleep duration and various cardiovascular events, the results have been inconsistent. Accordingly, we conducted a follow-up survey to investigate the relationship between sleep duration and cardiovascular events among male workers, accounting for occupational factors that might confound the true relationship. METHODS: A total of 2282 male employees aged 35-54 years based in a factory in Japan were followed for 14 years. The risk of cardiovascular events was compared among 4 groups stratified based on sleep duration at baseline (<6, 6-6.9, 7-7.9, and ≥8 hours). Cardiovascular events included stroke, coronary events and sudden cardiac death. The hazard ratios for events were calculated using a Cox proportional hazards model, with the 7-7.9-hour group serving as a reference. The model was adjusted for potential confounders including traditional cardiovascular risk factors and working characteristics. RESULTS: During 14 years of follow-up, 64 cardiovascular events were recorded including 30 strokes, 27 coronary events and 7 sudden cardiac deaths. After adjustment for possible confounders, the hazard ratios for cardiovascular and coronary events in the <6-hour group were 3.49 [95% confidence interval (95% CI) 1.30-9.40] and 4.95 (95% CI 1.31-18.73), respectively. There was no significant increment in the risk of stroke for any sleep duration groups. CONCLUSION: Short sleep duration (<6 hours) was a significant risk factor for coronary events in a Japanese male working population.

Association between long working hours and sleep problems in white-collar workers.

The purpose of this study is to examine the association between long work hours and sleep disturbance among white-collar workers. We evaluated 1510 male white-collar full-time employees, between the ages of 18 and 59 years, using a comprehensive sleep quality questionnaire, the Pittsburgh Sleep Quality Index (PSQI). All subjects worked in a light metal products factory in Japan. The mean number of monthly overtime work hours was determined using data from the previous 6 months from timecard records. Subjects were divided into five groups based on quintiles of the mean number of monthly overtime work hours: <26 h month(-1); ≥26 but <40; ≥40 but <50; ≥50 but <63; and >63. Leisure time physical activity, drinking habits just before sleep, presence of family/partner and health status were used as confounding factors in the multiple regression model. The prevalence of short sleep hours, impairment of sleep efficiency and daytime dysfunction among seven components of PSQI increased, in a dose-response relationship, with overtime work hours. The prevalence of high global score (>5.5 points) was highest in workers with overtime hours ≥50 h week(-1). The odds ratios after adjustment for confounding factors for high global score using less than 26 h as a reference group were 1.67 for workers with ≥50 h and <63 h, and 1.87 for workers with 63 h and more. To conclude, the present results suggest that long work hours correlate with reduced sleep quality in a dose-response manner.