Muscle grip strength predicts incident type 2 diabetes : population-based cohort study

Objectives To determine the longitudinal relationship of muscle mass and strength with incident type 2 diabetes, and previously unstudied mediating effects of testosterone and inflammation. Methods Community-dwelling male participants (aged ≥ 35 years) of the Men Androgen Inflammation Lifestyle Environment and Stress (MAILES) Study underwent biomedical assessment in 2002-2006 and 2007-2010, including hand grip strength (dynamometer), testosterone and inflammatory markers. Body composition (dual-energy X-ray absorptiometry) was assessed at baseline only. Incident type 2 diabetes was defined as a self-reported doctor diagnosis, diabetes medication use, fasting plasma glucose ≥ 7.0 mmol/L, or glycated haemoglobin ≥ 6.5% (48 mmol/mol) at follow-up, that was not present at baseline. Results Of n = 1632 men, incident type 2 diabetes occurred in 146 (8.9%). Muscle mass was not associated with incident type 2 diabetes. Grip strength was inversely associated with incident type 2 diabetes [unadjusted odds ratio (OR) per 5 kg: 0.87, 95% confidence interval (CI): 0.80-0.95; adjusted OR, 95% CI: 0.87, 0.78-0.97]. Arm muscle quality (grip strength divided by arm lean mass) was similarly associated with incident type 2 diabetes. Testosterone, IL-6 and TNF-α did not significantly mediate the associations. The population attributable fraction of type 2 diabetes from low grip strength was 27% (13-40%), assuming intervention could increase strength by 25%. Conclusions Reduced muscle strength, but not reduced muscle mass, is a risk factor for incident type 2 diabetes in men. This is not mediated by testosterone or inflammation. Intervention could prevent a substantial proportion of disease.