Abstract
BACKGROUND: The prevalence of cognitive impairment among older adults is rising, affecting daily living and increasing care burdens. This study explored the longitudinal relationship between education level and cognitive trajectories. And to the best of our knowledge, this study is the first to confirm the mediating role of urban-rural residence. METHODS: We analyzed data from 8,117 participants aged 45 and older in the Harmonized China Health and Retirement Longitudinal Study (CHARLS, 2011-2018). Participants were grouped by education level (illiterate, elementary/middle school, high school or above) and categorized into "persistently low" or "persistently high" cognitive trajectory groups based on their average cognitive z-scores over time. Multivariable logistic regression was used to assess the association between education, residence, and cognitive trajectories. Sensitivity analyses and E-values quantified the potential influence of unmeasured confounding factors. Mediation analysis examined the role of urban-rural residence in this relationship. RESULTS: Two cognitive trajectory patterns were identified: sustained high trajectory (57.7%) and sustained low trajectory (42.3%). Compared to illiterate participants, those with elementary or middle school education level had significantly lower risk of persistently low cognitive trajectory (Model 4: OR = 0.12, 95% CI: 0.10, 0.15). Urban residence was also independently associated with a reduced risk of persistently low cognitive trajectory (Model 4: OR = 0.60, 95% CI: 0.54, 0.66). Mediation analysis showed that urban-rural residence partially mediated the effect of education level on cognitive trajectory. Sensitivity analyses suggested the observed associations are moderately robust. CONCLUSION: Higher education level and urban residence are independently linked to persistently high cognitive trajectory in middle-aged and older Chinese adults, with urban-rural residence partially mediating the impact of education level. These findings highlight the enduring cognitive benefits of education level and suggest that improving living environments could enhance these effects, especially for those with lower education level. This study highlights the association between education level and cognitive trajectories in middle and old-aged adults in China. Urban-rural residence serves as a significant mediator, particularly for individuals with intermediate level of education.