Associations between physical activity trajectories and cognitive function in women 50 years and older: A nationally representative cohort study from the China Health and Retirement Longitudinal Study

OBJECTIVE: To examine the longitudinal association between physical activity trajectory changes and cognitive function in women aged 50 years and older. METHODS: Data were obtained from the China Health and Retirement Longitudinal Study, collected between 2011 and 2020, involving 2,760 women aged 50 years and older. Group-based trajectory modeling was used to identify four physical activity trajectory groups: Low-Fluctuation Group, Moderate-Increasing Group, Moderate-Stability Group, and High-Fluctuation Group. Cognitive function was assessed based on episodic memory and mental intactness. Linear mixed-effects models were employed to examine the association between physical activity trajectories and cognitive function, including interaction effects and age-stratified analyses. RESULTS: The Moderate-Increasing group was significantly associated with higher levels of global cognitive function (β = 0.45, 95% CI: 0.05-0.85) and episodic memory (β = 0.21, 95% CI: 0.05-0.37), particularly among women aged 50-59 years. In contrast, High-Fluctuation and Low-Fluctuation groups exhibited declining trends across cognitive outcomes. Age-stratified analysis suggested that the association between Moderate-Increasing group and cognitive function was not significant among women aged 60 years and older. CONCLUSION: In women aged 50-59 years, the Moderate-Increasing group was significantly associated with better global cognitive function and episodic memory; however, this association was attenuated or not observed in older age groups.