Longitudinal association of type 2 diabetes and insulin therapy with muscle parameters in the KORA-Age study

The aim of the current study was to investigate the association of type 2 diabetes (T2D) and insulin treatment with changes in muscle mass, muscle strength, and physical performance in older adults.

In 731 participants of the population-based KORA-Age study aged 74.6 ± 6.2 years (T2D: n = 118; insulin treatment: n = 20), skeletal muscle index (SMI [kg/m²]), hand grip strength (GS [kg]), and a timed up and go test (TUG [s]) were performed at baseline and after a follow-up time of 3 years. The association of T2D and insulin therapy with changes in muscle parameters was analyzed using linear regression models.

After adjustment for sex, age, BMI, physical activity, smoking, and multimorbidity, T2D was associated with the change in SMI during follow-up (β - 0.1 (95% CI - 0.3 to - 0.02) kg/m²; p = 0.02), but not with a change in GS (β - 0.9 (95% CI - 1.9 to 0.04) kg) or TUG (β - 0.1 (95% CI - 0.7 to 0.5) s). Insulin therapy was positively associated with change in SMI (β 0.6 (95% CI 0.3-0.9) kg/m²; p = 0.001), but not in GS (β - 1.6 (95% CI - 4.1 to 0.8) kg) or TUG (β 1.6 (95% CI - 0.2-3.4) s) in comparison with treatment with oral anti-diabetic medication alone.

Participants with T2D showed an accelerated decline in muscle mass compared to non-diabetic participants. Insulin therapy was associated with preserved muscle mass, but not muscle function parameters, indicating a discrepancy between muscle mass and function in this high-risk population.