Creatinine clearance, walking speed, and muscle atrophy: a cohort study.

Background: Chronic kidney disease is associated with malnutrition and inflammation. These processes may lead to loss of skeletal muscle and reduced physical performance. Associations of kidney function with muscle composition and longitudinal measures of physical performance are unknown.

Study Design: Prospective cohort study.

Setting & Participants: We evaluated 826 community-dwelling older adults enrolled in the Invecchiare in Chianti (InCHIANTI) Study who were free of baseline stroke or activities of daily living disability.

Predictor: Baseline creatinine clearance (Clcr) based on 24-hour urine collection.

Outcomes: Cross-sectional and longitudinal trajectories of physical performance measured by 7-m usual gait speed, 400-m fast gait speed, and knee extension strength using isometric dynamometry. Calf muscle composition assessed by quantitative computed tomography.

Results: Mean age of participants was 74 ± 7 (SD) years, with 183 having Clcr < 60 mL/min/1.73 m(2). After adjustment, each 10-mL/min/1.73 m(2) decrement in Clcr was associated with 0.01 (95% CI, 0.004-0.017) m/s slower 7-m usual walking speed and 0.008 (95% CI, 0.002-0.014) m/s slower 400-m walking speed. Each 10-mL/min/1.73 m(2) decrement in Clcr was associated with 28 (95% CI, 0.8-55) mm(2) lower muscle area and 0.15 (95% CI, 0.04-0.26) mg/cm(3) lower muscle density. After adjustment, lower Clcr was associated with slower mean 7-m (P=0.005) and 400-m (P=0.02) walk and knee extension strength (P=0.001) during the course of follow-up. During a mean follow-up of 7.1 ± 2.5 years, each 10-mL/min/1.73 m(2) lower baseline Clcr was associated with 0.024 (95% CI, 0.01-0.037) kg/y greater decline in knee strength.

Limitations: Single baseline measurement of Clcr and 3-year interval between follow-up visits may lead to nondifferential misclassification and attenuation of estimates.

Conclusions: Among older adults, lower Clcr is associated with muscle atrophy, reduced walking speed, and more rapid declines in lower-extremity strength over time.