Abstract
<title>Abstract</title> <p>As population aging accelerates alongside rapid digital transformation, whether digital engagement can delay the onset of cognitive impairment has become a question of growing public health and policy relevance. Using longitudinal data from the China Health and Retirement Longitudinal Study (CHARLS, 2011–2018), this study emulates a target trial to estimate the causal effect of sustained digital engagement on time-to-cognitive-impairment. We implement weighted discrete-time marginal structural models with stabilized inverse probability of treatment and censoring weights to address time-varying confounding, selective attrition, and reverse causation. Regular (≥weekly) digital engagement is associated with a significantly lower hazard of incident cognitive impairment and a clinically meaningful delay in onset. Counterfactual survival curves indicate a 7.4-month gain in restricted mean survival time over seven years under sustained engagement compared with non-engagement. Heterogeneity analyses reveal a compensatory pattern: the time-shift is largest among individuals with low education, rural residence, high social isolation, and lower baseline cognition. Pathway tests suggest that digital engagement operates through dual psychosocial mechanisms—psychological relief (reduced depressive symptoms) and enhanced social connectedness—with the psychological pathway exerting a relatively stronger influence. These findings move beyond static associations by demonstrating that digital engagement reshapes the temporal trajectory of cognitive aging. In aging societies, digital inclusion may therefore function not only as a technology policy but also as a scalable strategy for promoting cognitive health equity.</p>