Longitudinal Association Between Kidney Function Decline and Grip Strength Loss in Community‐Dwelling Older Adults: A 6‐Year Prospective Cohort Study

AIM: Age-related functional decline in muscle strength is a major determinant of disability in older adults. Although kidney dysfunction has been implicated in sarcopenia, longitudinal evidence linking changes in kidney function with muscle strength decline in community-dwelling older adults remains limited. This study, part of the Kusatsu Cohort Study, aimed to examine whether 6-year changes in estimated glomerular filtration rate (eGFR) were associated with changes in handgrip strength and skeletal muscle mass index (SMI). METHODS: A total of 279 residents in Kusatsu Town, Gunma Prefecture, aged ≥ 65 years participated in municipal checkups in 2019, 2021, 2023, and 2025. Handgrip strength, SMI, and eGFR (uncorrected for body surface area) were assessed. Six-year changes (Δgrip, ΔSMI, ΔeGFR) were calculated. Associations were examined using Pearson correlation and multivariable linear regression. ROC analysis evaluated the discriminatory ability of ΔeGFR for grip-strength decline. RESULTS: , p = 0.10). Δgrip correlated positively with ΔeGFR (r = 0.30, p < 0.001). In multivariable analysis, ΔeGFR independently predicted Δgrip (β = 0.14, p = 0.03), along with sex and baseline grip strength. ROC analysis showed moderate discrimination (AUC 0.664), with an optimal ΔeGFR cutoff of -0.263 over 6 years (-4.4%/year). CONCLUSIONS: Preservation of kidney function was independently associated with a smaller decline in handgrip strength among community-dwelling older adults. These findings highlight kidney-muscle crosstalk as a key mechanism of functional aging and support the use of eGFR decline as a biomarker for early detection of strength deterioration.