Independent and Combined Associations of Handgrip and Knee Extension Strength With Cognitive Function in Community-Dwelling Older Adults

OBJECTIVES: To examine the independent and combined associations of handgrip strength (HGS) and knee extension strength (KES) with global cognition in community-dwelling older adults. DESIGN: Cross-sectional analysis of baseline data from a prospective cohort. SETTING AND PARTICIPANTS: A total of 279 community-dwelling adults aged 65 years or older living independently (mean age 76.8 ± 5.9; 26.5% men). METHODS: Low strength was defined as the sex-specific lowest quartile (Q1). Multiple linear regression estimated differences in Mini-Mental State Examination (MMSE) scores adjusting for age, sex, education, and depressive symptoms (GDS-15). We examined (1) HGS and KES together, (2) 4 exclusive groups (low KES only, low HGS only, both low, neither), and (3) sensitivity analyses including skeletal muscle index and sex-stratified analyses using weight-normalized KES. RESULTS: Low KES related to lower MMSE (Model 1 B, -0.882; 95% CI, -1.542 to -0.223, P = .009; Model 2 B, -0.892; 95% CI, -1.564 to -0.219; P = .010). Low HGS was not significant (P ≥ .27). When both were included, low KES remained significant (B, -0.814; 95% CI, -1.509 to -0.119; P = .022) but low HGS did not. In 4-group analysis, both low KES and HGS vs neither showed lower MMSE (B, -1.054; 95% CI, -1.984 to -0.112; P = .027). Associations for KES persisted after adjusting for skeletal muscle index (B, -0.842; 95% CI, -1.522 to -0.161; P = .016). In sex-stratified models, weight-normalized KES was associated with MMSE in men (B, 6.598; 95% CI, 2.258 to 10.939; P = .004) but not in women. CONCLUSIONS AND IMPLICATIONS: Lower KES shows a consistent and independent association with global cognition; combined weakness in upper and lower limbs signals greater cognitive deficit. Adding KES to community screening may improve early detection of cognitive vulnerability.