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Cigarette smoking is the leading avoidable cause of disease burden. Observational studies have suggested an association between smoking and risk of type 2 diabetes mellitus (T2DM). We conducted a meta-analysis of prospective observational studies to investigate the association of smoking status, smoking intensity, and smoking cessation with the risk of T2DM in Japan, where the prevalence of smoking has been decreasing but remains high. We systematically searched MEDLINE and the Ichushi database to December 2015 and identified 22 eligible articles, representing 343,573 subjects and 16,383 patients with T2DM. We estimated pooled relative risks (RRs) using a random-effects model and conducted subgroup analyses by participant and study characteristics. Compared with nonsmoking, the pooled RR of T2DM was 1.38 (95% confidence interval [CI], 1.28–1.49) for current smoking (19 studies) and 1.19 (95% CI, 1.09–1.31) for former smoking (15 studies). These associations persisted in all subgroup and sensitivity analyses. We found a linear dose-response relationship between cigarette consumption and T2DM risk; the risk of T2DM increased by 16% for each increment of 10 cigarettes smoked per day. The risk of T2DM remained high among those who quit during the preceding 5 years but decreased steadily with increasing duration of cessation, reaching a risk level comparable to that of never smokers after 10 years of smoking cessation. We estimated that 18.8% of T2DM cases in men and 5.4% of T2DM cases in women were attributable to smoking. The present findings suggest that cigarette smoking is associated with an increased risk of T2DM, so tobacco control programs to reduce smoking could have a substantial effect to decrease the burden of T2DM in Japan. •This meta-analysis examined smoking and diabetes risk among Japanese.•Current and former smokers showed a higher risk of diabetes than non-smokers.•Diabetes risk linearly increased with higher consumption of cigarettes.•Diabetes risk steadily decreased after smoking cessation.

Background We examined the prospective associations of changes in lifestyle behaviors before/during the COVID-19 pandemic, namely physical activity and screen time, with mental health. Furthermore, the impacts of physical activity and screen time on mental health during the pandemic were examined cross-sectionally. Methods A two-wave longitudinal study was conducted among 2423 children and adolescents in Shanghai, China. Lifestyle behavior variables (physical activity and screen time) and psychological variables (depressive symptoms, anxiety, and stress) were measured using a self-reported questionnaire in January and March 2020. A series of multivariable logistic regressions were performed to examine the associations between changes in lifestyle behaviors in two waves and psychological problems. The combined associations of physical activity and screen time with psychological problems were also explored using the second wave data. Results Compared to students with persistently short screen time before and during the COVID-19 pandemic, those with prolonged screen time (OR = 1·36 for depression, OR = 1·48 for anxiety) and those with persistently long screen time (OR = 1·70 for depression, OR = 2·13 for anxiety) reported a higher risk of psychological symptoms. The association between changes in physical activity and psychological symptoms was not statistically significant after adjustment for demographic factors, socioeconomic status, and screen time. During the COVID-19 pandemic, engaging in longer screen time (OR = 1·44 for depression, OR = 1·55 for anxiety) was associated with worsened psychological conditions, while engaging in increased physical activity (OR = 0·58 for depression, OR = 0·66 for anxiety) was associated with better psychological conditions. Conclusions Our study suggests that promoting physical activity and limiting leisure screen time during the COVID-19 pandemic are important to prevent and mitigate psychological problems in children and adolescents. Therefore, effective interventions targeting lifestyle behaviors are needed to protect children and adolescents’ physical and mental health.

Amino acids have emerged as novel biomarkers for predicting type 2 diabetes (T2D), but the epidemiologic data linking circulating amino acid profiles with T2D are sparse in Asian populations. We conducted a nested case-control study within a cohort of 4,754 nondiabetic Japanese employees who attended a comprehensive health checkup in 2008–2009 and agreed to provide blood samples. During a 5-year follow-up, incident T2D cases were ascertained based on plasma glucose, glycated hemoglobin, and self-report. Two controls matched to each case on sex, age, and the date of serum sampling were randomly selected by using density sampling, resulting in 284 cases and 560 controls with amino acid measures. High concentrations of valine, leucine, isoleucine, phenylalanine, tyrosine, alanine, glutamate, ornithine, and lysine were associated with an increased risk of incident T2D, in a linear manner. High glutamine concentrations were associated with a decreased risk of incident T2D. Further adjustment for the homeostasis model assessment of insulin resistance attenuated these associations. Overall, these amino acids may be novel useful biomarkers in the identification of people at risk of T2D before overt symptoms. Insulin resistance may account for or mediate the relationship between these amino acids and risk of incident T2D.

Objective To examine the association between adherence to the Japanese Food Guide Spinning Top and total and cause specific mortality.Design Large scale population based prospective cohort study in Japan with follow-up for a median of 15 years.Setting 11 public health centre areas across Japan.Participants 36 624 men and 42 970 women aged 45-75 who had no history of cancer, stroke, ischaemic heart disease, or chronic liver disease.Main outcome measures Deaths and causes of death identified with the residential registry and death certificates.Results Higher scores on the food guide (better adherence) were associated with lower total mortality; the multivariable adjusted hazard ratios (95% confidence interval) of total mortality for the lowest through highest scores were 1.00, 0.92 (0.87 to 0.97), 0.88 (0.83 to 0.93), and 0.85 (0.79 to 0.91) (P<0.001 for trend) and the multivariable adjusted hazard ratio associated with a 10 point increase in food guide scores was 0.93 (0.91 to 0.95; P<0.001 for trend). This score was inversely associated with mortality from cardiovascular disease (hazard ratio associated with a 10 point increase 0.93, 0.89 to 0.98; P=0.005 for trend) and particularly from cerebrovascular disease (0.89, 0.82 to 0.95; P=0.002 for trend). There was some evidence, though not significant, of an inverse association for cancer mortality (0.96, 0.93 to 1.00; P=0.053 for trend).Conclusion Closer adherence to Japanese dietary guidelines was associated with a lower risk of total mortality and mortality from cardiovascular disease, particularly from cerebrovascular disease, in Japanese adults.

Epidemiological evidence on the effects of a long‐term low‐carbohydrate diet (LCD) on cancer incidence remains sparse. We investigate the association between LCD and the risk of overall and specific cancer site incidence in a Japanese population‐based prospective cohort study among 90 171 participants aged 45‐74. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). During a median 17.0 y of follow‐up, we identified 15 203 cancer cases. A higher overall LCD score was associated with increased overall cancer risk (HR = 1.08 [CI: 1.02‐1.14], P‐trend = .012), while it was associated with decreased gastric cancer (GC) risk (0.81 [0.71‐0.93], P‐trend = .006). A higher animal‐based LCD score was associated with higher risk of overall cancer (1.08 [1.02‐1.14], P‐trend = .003), colorectal cancer (CRC) (1.11 [0.98‐1.25], P‐trend = .018), rectal cancer (RC) (1.24 [1.00‐1.54], P‐trend = .025), lung cancer (LC) (1.16 [1.00‐1.34], P‐trend = .042), and lower risk of GC (0.90 [0.79‐1.01], P‐trend = .033). Furthermore, we found that plant‐based LCD score was related to lower GC incidence (0.87 [0.77‐0.99], P‐trend = .031). Additionally, adjusted for plant fat intake amplified the adverse associations (overall cancer: 1.08 [1.02‐1.14] vs. 1.11 [1.05‐1.18]; CRC: 1.08 [0.95‐1.22] vs. 1.13 [0.99‐1.30]; LC: 1.14 [0.98‐1.33] vs. 1.19 [1.01‐1.41]). We conclude that LCD enriching with animal products was associated with increased overall cancer, CRC, and LC incidence. These adverse associations could be attenuated by plant fat consumption. LCD reduces the risk of developing GC. Long‐term adherence to LCD without paying attention to the balance between animal and plant food source consumption might cause adverse overall cancer incidence consequences. Epidemiological evidence on the effects of a long‐term low‐carbohydrate diet (LCD) on cancer incidence remains sparse. In this cohort study, the authors found that a higher animal‐based LCD score was associated with a higher risk of overall cancer, colorectal cancer, lung cancer, and a lower risk of gastric cancer (GC). A plant‐based LCD score was associated with decreased GC incidence.

People in Japan have the longest life expectancy at birth in the world. Here, we compile the best available evidence about population health in Japan to investigate what has made the Japanese people healthy in the past 50 years. The Japanese population achieved longevity in a fairly short time through a rapid reduction in mortality rates for communicable diseases from the 1950s to the early 1960s, followed by a large reduction in stroke mortality rates. Japan had moderate mortality rates for non-communicable diseases, with the exception of stroke, in the 1950s. The improvement in population health continued after the mid-1960s through the implementation of primary and secondary preventive community public health measures for adult mortality from non-communicable diseases and an increased use of advanced medical technologies through the universal insurance scheme. Reduction in health inequalities with improved average population health was partly attributable to equal educational opportunities and financial access to care. With the achievement of success during the health transition since World War 2, Japan now needs to tackle major health challenges that are emanating from a rapidly ageing population, causes that are not amenable to health technologies, and the effects of increasing social disparities to sustain the improvement in population health.

Background: Although previous research has focused on the association between long working hours and several mental health outcomes, little is known about the association in relation to mental health-related sickness absence, which is a measure of productive loss. We aimed to investigate the association between overtime work and the incidence of long-term sickness absence (LTSA) due to mental disorders.Methods: Data came from the Japan Epidemiology Collaboration on Occupational Health Study (J-ECOH). A total of 47,422 subjects were followed-up in the period between April 2012 and March 2017. Information on LTSA was obtained via a study-specific registry. Baseline information was obtained at an annual health checkup in 2011; overtime working hours were categorized into <45; 45–79; 80–99; and ≥100 hours/month.Results: During a total follow-up period of 211,443 person-years, 536 people took LTSA due to mental disorders. A Cox proportional hazards model showed that compared to those with less than 45 hours/month of overtime work, those with 45–79 hours/month were at a lower risk of LTSA due to mental health problems (hazard ratio [HR] 0.63; 95% confidence interval [CI], 0.56–0.71) while those with overtime work of ≥100 hours/month had a 2.11 (95% CI, 1.12–3.98) times higher risk of LTSA due to mental health problems.Conclusion: Engaging in excessive overtime work was linked with a higher risk of LTSA due to mental health problems while the lower risk observed among individuals working 45–79 hours/month of overtime work might have been due to a healthy worker effect.

Physical activity has been linked to a lower risk of chronic kidney disease (CKD); however, evidence on the relationship between domain-specific physical activity and CKD is scarce. This study aimed to examine the risk of CKD in relation to leisure-time, occupational, and commuting physical activities in a large occupational cohort in Japan. Participants were 17,331 workers (20–65 years old) without CKD and were followed-up for a maximum period of 13 years. Incident CKD was defined as an estimated glomerular filtration rate of < 60 mL/min/1.73 m 2 and/or proteinuria determined using the dipstick test. The Cox proportional hazards models were used to examine the associations. During 147,752 person-years of follow-up, 4013 participants developed CKD. Workers who were standing or walking at work and those who were fairly active at work had adjusted hazard ratios of 0.88 (95% confidence interval 0.86–0.96) and 0.89 (95% confidence interval 0.78–1.02), respectively, for developing CKD than sedentary workers. Leisure-time physical activity and walking for commute were not associated with CKD risk. Our findings suggest that occupational, but not leisure-time and commuting physical activities, is associated with a lower CKD risk.

This study examined the association of green tea consumption with influenza among Japanese workers in the Kanto and Tokai areas. We conducted a case-control study in a cohort of 4302 workers. Consumption frequency of green tea in 2011 and physician-diagnosed influenza that occurred over the winter season from November 2011 through April 2012 were ascertained using a self-administered questionnaire. Two controls matched by company, sex, and age (and checkup date in one company) were randomly selected for each case. Odds ratio of influenza were estimated by conditional logistic regression. One hundred and seventy-nine cases and 353 controls with complete data were included in the analysis. Green tea consumption was significantly associated with decreased odds of developing influenza; the multivariable-adjusted odds ratio for green tea consumption of ≥5 cups/week was 0.61 (95% CI 0.39–0.95) compared with <1 cup/week (P for trend = 0.028). When analysis was restricted to cases confirmed using a diagnostic kit, the corresponding value was 0.68 (95% CI 0.39–1.18; P for trend = 0.16). Our data suggest that green tea consumption is associated with a lower risk of influenza. The present findings require confirmation in large-scale prospective studies using diagnostic tool for influenza infection.

Increasing attention is being paid to the role of diet quality in the prevention and management of non-communicable diseases. We developed a scoring system for the traditional Japanese diet and its modified version considering the dietary culture in Japan, dietary guidelines for the Japanese, and updated evidence for disease prevention. The traditional Japanese diet comprises white rice, miso soup, soybean products, vegetables, mushrooms, seaweeds, fish and shellfish, high-sodium foods, and green tea. In the modified Japanese diet, unprocessed or minimally refined rice and raw vegetables, milk and dairy products, and fruits were additionally considered, while salty food was reverse-scored. The cutoff for the intake frequency of each food/food group was determined with reference to a health survey of >12,000 workers. Among the participants in the validation study, we confirmed the nutritional gradient with increasing scores in the expected direction. The scores were closely correlated with the respondents’ backgrounds, including occupational factors. This simple scoring system can be used for diet quality assessments and epidemiological research.