Context: Skeletal muscle plays a key role in glucose regulation, yet the association between muscle quantity or quality and the risk of developing type 2 diabetes has not been explored.
Objective: The objective of the study was to assess the association between muscle quantity and strength and incident diabetes and to explore whether this association differs by body mass index (BMI) category.
Design and setting: Participants were 2166 older adults in the Health, Aging, and Body Composition Study who were free of diabetes at baseline (1997–1998). Computed tomography and dual-energy x-ray absorptiometry were used to measure abdominal and thigh muscle area and total body lean mass, respectively. Strength was quantified by grip and knee extensions.
Main outcome measure: Incident diabetes, defined as fasting glucose of 126 mg/dL or greater, a physician's diagnosis, and/or the use of hypoglycemic medication were measured.
Results: After a median 11.3 years of follow-up, there were 265 incident diabetes cases (12.2%). In fully adjusted models, no association was found between muscle or strength measures and incident diabetes (for all, P > .05). For women, there was a significant interaction with BMI category for both abdominal and thigh muscle, such that greater muscle predicted lower risk of incident diabetes for normal-weight women (hazard ratio 0.37 [0.17–0.83] and 0.58 [0.27–1.27] per SD, respectively) and a greater risk for overweight and obese women (hazard ratio 1.23 [0.98–1.54] and 1.28 [1.00–1.64], respectively). No significant interactions by BMI category existed for strength measures or any measures for men (for all, P > .05).
Conclusions: Greater muscle area is associated with a lower risk of incident diabetes for older normal-weight women but not for men or overweight women.