Role of muscle mass and muscle quality in the association between diabetes and gait speed

Abstract

Objective: Older people with type 2 diabetes are at high risk of mobility disability. We investigated the association of diabetes with lower-limb muscle mass and muscle quality to verify whether diabetes-related muscle impairments mediate the association between diabetes and low walking speed.

Research design and methods: We performed a cross-sectional analysis of 835 participants (65 years old and older) enrolled in the InCHIANTI (Invecchiare in Chianti, aging in the Chianti area) population-based study. Total, muscular, and fat cross-sectional areas of the calf and relative muscle density were measured using peripheral quantitative computerized tomography. Indicators of muscle performance included knee-extension torque, ankle plantar flexion and dorsiflexion strength, lower-extremity muscle power, and ankle muscle quality (ratio of ankle strength to the muscle area [kilograms per centimeters squared]). Gait performance was assessed by 4- and 400-m walking speed. Diabetes was ascertained by standard American Diabetes Association criteria.

Results: Prevalence of diabetes was 11.4%. After adjustment for age and sex, participants with diabetes had lower muscle density, knee and ankle strength, and muscle power and worse muscle quality (all P < 0.05). Diabetic participants were also slower on both 4-m (β: -0.115 ± 0.024 m/s, P < 0.001) and 400-m (β:-0.053 ± 0.023 m/s, P < 0.05) walking tests. In multivariable linear regression models, lower-limb muscle characteristics accounted for 24.3 and 15.1% of walking speed difference comparing diabetic and nondiabetic subjects in the 4- and 400-m walks, respectively.

Conclusions: In older persons, diabetes is associated with reduced muscle strength and worse muscle quality. These impairments are important contributors of walking limitations related to diabetes.

Figure 1

Percent reduction in the association between diabetes and gait speed after adjustment for all potential mediators of the association (fully adjusted), for all muscular mediators, and for individual covariates. Bars show the reduction in β coefficient (from linear regression models) for diabetes compared with basic model (age and sex): [1 − (β adjusted/β basic)]. Gray bars, 4-m gait speed; black bars, 400-m gait speed.