Revisiting social and psychological pathways linking late-life depression and cognitive impairment

Late-life depression (LLD) and mild cognitive impairment (MCI) frequently co-occur and impose a heavy burden on older adults, yet the psychological mechanisms linking them remain poorly understood. Using six nationally or regionally representative longitudinal ageing cohorts (CHARLS, ELSA, HRS, LASI, MHAS, and SHARE), we examined the association between LLD and MCI in the global population and tested whether commonly hypothesized psychological pathways (functional impairment, social isolation, physical inactivity, and poor sleep) mediate this relationship. At the population level, LLD was significantly associated with MCI (ORs = 1.27–3.39), and Cox models indicated bidirectional risk (HRs = 1.09–1.27). However, Random Intercept Cross-Lagged Panel Models provided limited evidence for within-person effects, with no candidate factors mediating this association. Together, these findings challenge prevailing assumptions that modifiable psychological factors drive the dynamic coupling between depression and cognitive decline, instead suggesting that their co-development reflects long-term vulnerability established earlier in the life course.