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No information exists regarding the effects of working hours on glucose metabolism in adults with pre-diabetes, a high-risk group for developing diabetes. Further, longitudinal patterns in working hours and their effects on glucose metabolism have not been described previously. We investigated the association between changes in overtime working hours over 3 years and the risk for progression to type 2 diabetes among adults with pre-diabetes. We analyzed patterns of overtime working hours from 2008 to 2011 among 18,172 workers in Japan (16,474 men, aged 30 to 64 years) with pre-diabetes in 2011 (baseline) using the sub-cohort data from the Japan Epidemiology Collaboration on Occupational Health Study. Participants were followed up to March 2016. Overtime working hours per month were self-reported annually in 2008-2011 and trajectory patterns were identified using group-based trajectory modeling. Type 2 diabetes was diagnosed by fasting or random plasma glucose test, hemoglobin A1c, and history of diabetes. Multivariable-adjusted hazard ratios of incident diabetes were calculated using Cox regression. We identified 3 distinct trajectories of overtime work: persistently short, long-to-short, and persistently long. During a mean follow-up of 3.5 years, 1613 participants (8.9%) developed diabetes. Compared with persistently short overtime working hours, no material increase in diabetes risk was observed for either long-to-short working hours or persistently long working hours. After adjustment for potential confounders, this association was materially unchanged. The results suggest that among individuals with pre-diabetes, persistently long working hours over 3 years were not associated with an increased risk of developing type 2 diabetes. [ABSTRACT FROM AUTHOR]

We prospectively examined diabetes risk in association with a summary measure of degree and duration of weight change. The study participants were 51,777 employees from multiple companies in Japan, who were aged 30-59years, free of diabetes at baseline, and followed up for 7years (2008-2015). Exposure was cumulative body mass index (BMI)-years, which was defined as the area of BMI units above or below baseline BMI during follow-up, and was treated as a time-dependent variable in the Cox proportional hazards regression models. During the 263,539 person-years of follow-up, 3465 participants developed diabetes. The adjusted hazard ratio (HR) of diabetes for a 1-unit increase in cumulative BMI-years was 1.11 (95% confidence interval (CI): 1.09, 1.12). The association was more pronounced among overweight (HR=1.11; 95% CI: 1.08, 1.14) and obese (HR=1.12; 95% CI: 1.08, 1.15) adults compared with normal- and under-weight (HR=1.07; 95% CI: 1.03, 1.11) adults (P for interaction of cumulative BMI-years X baseline BMI-group=0.002). The association of higher cumulative BMI-years with incident diabetes did not substantially differ by metabolic phenotype. The present results emphasize the importance of avoiding additional weight gain over an extended period of time for the prevention of type 2 diabetes, especially among overweight and obese adults, irrespective of metabolic health status. [ABSTRACT FROM AUTHOR]