Strength training and risk of type 2 diabetes in a Japanese working population: A cohort study

AIMS/INTRODUCTION Muscle strength training has been suggested to improve glucose metabolism; however, epidemiological evidence regarding strength training's effects on diabetes risk is scarce. We prospectively examined the association between strength training and the risk of type 2 diabetes in Japanese men and women. MATERIALS AND METHODS The sample included health checkups on 26,630 Japanese male and female workers aged 30-64 years without diabetes at baseline. Weekly time spent on strength training was elicited using a self-reported questionnaire. Type 2 diabetes was diagnosed based on hemoglobin A1c, fasting glucose, random plasma glucose and self-report in an annual health checkup. Hazard ratio (HR) and its 95% confidence interval (CI) for incident diabetes was estimated using a Cox proportional hazards model. RESULTS During a mean follow up of 5.2 years with 139,748 person-years, 1,770 individuals developed diabetes. Age- and sex-adjusted HR for diabetes was 0.58 (95% CI 0.42-0.79) in those who engaged in strength training compared with those who engaged in no strength training. After further adjusting for potential confounders, the corresponding HR was 0.66 (95% CI 0.48-0.90). Additional adjustment for body mass index did not materially change the result; the HR was 0.70 (95% CI 0.51-0.96). The association was more pronounced in individuals aged 50 years or older than those aged <50 years, although the difference in the association by age was not significant. CONCLUSIONS These results suggest that engagement in strength training could help to reduce the risk of type 2 diabetes in a Japanese working population.