To analyze the mediating role of activities of daily living ability in older adults and the long-term relationship between cognitive trajectories and the risk of all-cause mortality.

Based on the CLHLS data from 2002 to 2008, the Group-based Trajectory model (GBTM) was used to identify the heterogeneous trajectories of cognitive function in older adults, using CLHLS data from 2008 to 2018 as the follow-up time for all-cause mortality risk. The connection between the cognitive trajectories and the risk of all-cause mortality was analyzed using Kaplan-Meier survival curves, Log-Rank tests and Cox regression analysis. Marginal structure model was used to analyze the mediating effect of ADL in their relationship, with subgroup analysis and sensitivity analysis conducted.

A total of 4 177 older adults aged 65-105 years who participated in follow-up for three consecutive years were enrolled, and two cognitive trajectory groups were identified: the low-decline group (n=691, 16.61%) and the high-stable group (n=3 186, 83.39%). By Log-Rank test, there was a statistically significant difference in survival rate between the different cognitive trajectory groups (χ²=323.69, P<0.01). After adjusting for other covariates, the risk of all-cause death was still lower in the high-stable group (HR=0.64, 95%CI: 0.57-0.71) compared to the low-declining group. ADL had a mediating effect in the relationship between cognitive trajectories and the risk of all-cause mortality, and the indirect hazard ratio was 0.93 (95%CI: 0.87-0.98). The results of subgroup analysis and sensitivity analysis were consistent with the trend of the main research results.

There are different cognitive trajectories in the elderly, and cognitive trajectories can affect the risk of all-cause mortality, ADL plays a mediating role in this relationship. Therefore, it is necessary to dynamically monitor cognition, detect problems in time, and take targeted measures to reduce the risk of death in the elderly.