Associations of Impaired Renal Function with Declines in Muscle Strength and Muscle Function in Older Men: Findings from the CHAMP Study

Background: Advanced kidney disease is associated with reduced muscle strength and physical performance. However, associations between early stages of renal impairment and physical outcomes are unclear. Methods: The Concord Health and Ageing in Men Project is a prospective study of 1,705 community-dwelling men aged 70 years and older. Participants with estimated glomerular filtration rate (eGFR) more than 30 mL/min/1.73 m² were included and further divided into four eGFR categories. Physical parameters including grip strength, gait speed, appendicular lean mass (ALM, a sum of skeletal mass of arms and legs), ALM adjusted for body mass index (ALM_BMI), and muscle function (measured using grip strength divided by arm lean mass) were assessed at both baseline and 5-year follow-up. Associations between kidney function and changes in physical parameters were analyzed using linear and logistic regression models. Results: Our study included 789 men with a median age of 75 years and median eGFR of 72 mL/min/1.73 m² at baseline. Over 5 years, grip strength, gait speed, ALM_BMI, and muscle function all declined in the whole cohort, compared with baseline. The multivariable analyses showed that poorer renal function was associated with more rapid declines in grip strength, gait speed, and muscle function in participants with mild-to-moderate renal impairment (GFR category stage G3, eGFR < 60 mL/min/1.73 m²) (p =. 01, p <. 01, p =. 02, respectively) but less so in those with eGFR more than 60 mL/min/1.73 m², whereas eGFR category did not have a significant impact on declines in ALM_BMI. These results remained unchanged with or without adjustment for age. Conclusions: In community-dwelling older men, mild-to-moderate renal impairment at baseline was associated with declines in grip strength, gait speed, and muscle function over time despite preservation of muscle mass.