Cognition and arthritis in adults over 50: Evidence from CHARLS, HRS, and ELSA.

INTRODUCTION: Arthritis and cognitive decline are significant health challenges in ageing populations, yet their association across diverse socioeconomic and cultural contexts remains insufficiently understood. This study examines the relationship between cognitive function and arthritis prevalence among adults aged 50 years and older, utilising data from 3 longitudinal ageing cohorts: the China Health and Retirement Longitudinal Study (CHARLS), the Health and Retirement Study (HRS), and the English Longitudinal Study of Ageing (ELSA).

METHOD: The analysis included 18,562 participants from CHARLS, 23,238 from HRS, and 9848 from ELSA, all aged =50 years with physician-diagnosed arthritis and cognitive assessments. Cognitive function was evaluated across memory, orientation, and executive function domains, standardised as z-scores within each cohort. Generalised Estimating Equations (GEE) and Generalised Linear Mixed Models assessed the longitudinal association between cognition and arthritis, adjusting for sociodemographic factors, lifestyle variables, and comorbidities. Sensitivity analyses validated the findings- robustness.

RESULTS: In fully adjusted GEE models, executive function was significantly associated with arthritis. Each 1-standard deviation (SD) lower executive score was associated with higher arthritis odds: CHARLS odds ratio (OR) 1.000 (95% confidence interval [CI] 1.000-1.001, P=0.016), HRS OR 1.13 (95% CI 1.01-1.28, P=0.037), and ELSA OR 1.07 (95% CI 1.02-1.12, P=0.009). Neither episodic memory nor orientation showed significant associations (all P>0.10), and total cognition in HRS was significant. Mixed-model estimates were concordant, and alternative correlation structures yielded consistent executive- arthritis links.

CONCLUSION: Across 3 major ageing cohorts, impaired executive function is independently associated with higher odds of arthritis in adults aged =50 years. Targeting executive deficits may enhance early identification and integrated management of arthritis and cognitive health in ageing populations.