Physical activity trajectories and cognitive decline among older adults in China: a longitudinal cohort study.

BACKGROUND: Cognitive decline is a critical public health concern among older adults. While physical activity (PA) is a recognized modifiable factor for mitigating cognitive deterioration, the specific impact of long-term PA trajectories on the rate of cognitive decline remains understudied, particularly in China. METHODS: A longitudinal cohort of 3,471 participants aged ≥ 60 years from the China Health and Retirement Longitudinal Study (CHARLS) was analyzed. PA trajectories were identified via group-based trajectory modeling (GBTM) on the basis of self-reported PA data from four waves (2011, 2013, 2015, and 2018). Global cognitive function, assessed by episodic memory and mental intactness, was measured repeatedly. Associations between PA trajectories and cognitive decline were analyzed using linear mixed models adjusted for demographic, lifestyle, and health-related factors. RESULTS: Two distinct PA trajectories were identified: a high decreasing trajectory group (43.4%) and a low increasing trajectory group (56.6%). The high decreasing trajectory group initially had higher PA levels but experienced a slight decline, whereas the low increasing trajectory group started with lower PA levels but showed gradual increases. Participants in the high decreasing trajectory group exhibited significantly slower declines in global cognition (β = 0.106, 95% CI: 0.072, 0.140, P < 0.001) and mental intactness (β = 0.116, 95% CI: 0.078, 0.154, P < 0.001) compared to the low increasing trajectory group. Subgroup analysis revealed that participants aged ≥ 75 years, females, those with higher education levels, and rural residents experienced slower cognitive decline. Sensitivity analyses confirmed the robustness of these findings. CONCLUSIONS: Sustaining higher levels of physical activity over time is associated with a slower rate of cognitive decline in older Chinese adults. This protective effect is especially pronounced in specific demographic subgroups.