The Longitudinal Relationship Between Physical Functions and Cognitive Functions Among Middle-Aged and Older Adults in Primary Care

(1) Background: Gait speed (GS) and handgrip strength (HGS) have been identified as factors in cognitive impairment, depression, sleep problems, and quality of life. This study aims to comprehensively investigate the longitudinal relationship between physical functions (gait speed and handgrip strength) and cognitive functions, as well as cognitive decline, in middle-aged and older adults in China. (2) Methods: Using longitudinal data from the China Health and Retirement Longitudinal Study (CHARLS), we analyzed 1903 subjects aged 60 and above with repeated measurements of GS, and 4218 subjects aged 45 and above with repeated measurements of HGS. The cognitive functions we considered included drawing ability, word recall, TICS-10, and an overall cognitive score (OCS). Mixed-effect logistic and linear regression were used to analyze the association between GS/HGS and cognitive functions in middle-aged and older adults with repeated measurements. (3) Results: A faster GS is associated with better drawing ability (OR = 1.33, <i>p</i> = 0.045) and TICS-10 (OR = 1.60, <i>p</i> = 0.024). A stronger HGS is associated with higher odds of drawing ability (OR = 1.36, <i>p</i> = 0.012) and better TICS-10 (OR = 1.41, <i>p</i> = 0.018). Both weak HGS and slow GS are significantly associated with a higher decline in cognitive function, while HGS is more predictive of the decline for women and GS is more predictive for men. (4) Conclusions: Both GS and HG are positively associated with cognitive functions cross-sectionally and longitudinally in middle-aged and older adults. Health interventions targeting HGS and GS may help improve cognitive functions. Future research is warranted to establish the causal relationship between these interventions and improvements in cognitive functions.