The association between upper limb function, physical exercise, and cognitive ability among empty-nest elderly in China: A cross-sectional study based on CLHLS

Background: The rapid aging of China’s population poses serious challenges to the cognitive health of older adults living without co-resident children (empty-nest older adults). Currently, the role of upper limb function on the cognitive function of this group and its potential pathway of effect through physical exercise remain unclear. Objective: This study aimed to explore the associations among upper limb function, physical exercise, and cognitive ability in the Chinese empty-nest elderly population, and to explore the potential mediating role of physical exercise in the relationship between upper limb function and cognition. Due to the cross-sectional design, no causal relationships can be established; all reported associations are statistical in nature. Methods: This study employed a cross-sectional design using data from the 2018 Chinese Longitudinal Healthy Longevity Survey (CLHLS). Based on household structure information, older adults aged 60 and above who did not live with their children were defined as “empty-nest elderly”. A total of 5,060 empty-nest elderly were included in the final analysis. Upper limb function (normal/restricted), physical exercise (yes/no), and cognitive ability (normal/impaired) were assessed via questionnaire. Analyses included multivariable logistic regression, restricted cubic spline curves, Bootstrap-based mediation effect analysis, and subgroup analysis. Results: Among the 5,060 participants (mean age 78.60 ± 10.31 years), 755 (14.92%) had cognitive impairment. Multivariable-adjusted analysis showed that restricted upper limb function was significantly positively associated with the risk of cognitive impairment (OR=2.55, 95% CI: 1.95–3.29), while regular physical exercise was significantly negatively associated with this risk (OR=0.77, 95% CI: 0.62–0.95). Mediation analysis indicated that physical exercise accounted for 5.95% of the total effect (ACME = 0.0121, 95% CI: 0.0074–0.0172). Given the small effect size, this pathway should be interpreted as a minor statistical contributor rather than a dominant mechanism. Subgroup analysis showed that the association of upper limb function and physical exercise with cognitive impairment was significantly modified by drinking status (both P for interaction