["Geriatrics &Gerontology International, Volume 26, Issue 6, June 2026. ", "\nDecline in kidney function was associated with accelerated loss of grip strength over 6 years in community‐dwelling older adults. Monitoring eGFR trajectories may help identify individuals at risk of functional decline.\n\nABSTRACT\n\nAim\nAge‐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).\n\n\nMethods\nA 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.\n\n\nResults\nGrip strength declined significantly over 6 years (28.5 ± 8.8–24.0 ± 7.6 kg, p < 0.001), whereas SMI remained stable (6.3 ± 1.0 to 6.2 ± 1.0 kg/m2, 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).\n\n\nConclusions\nPreservation 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.\n\n"]