Stroke and cognitive decline: associations of social support and family connections in CHARLS and ELSA cohorts

Background Stroke is associated with accelerated cognitive decline in older adults, but whether social support and family connections statistically moderate this association has rarely been tested formally in longitudinal, cross-national data. Methods We analyzed the China Health and Retirement Longitudinal Study (CHARLS; N = 11,569; Wave 1 [2011] baseline to Wave 4 [2018], up to 7.2 years) and the English Longitudinal Study of Ageing (ELSA; N = 5,713; Wave 3 [2006–2007] baseline to Wave 9 [2019], up to 13.0 years). Cognitive function was assessed with a harmonized composite (orientation, immediate and delayed word recall, plus pentagon drawing in CHARLS). Linear mixed-effects models with random intercepts and slopes estimated the incident-stroke × time interaction (annual cognitive decline, points/year), adjusting for age, sex, BMI, education, marital status, smoking, drinking, comorbidity count, and residence (CHARLS only). A three-way interaction (stroke × social support/family connection × time) formally tested moderation. Propensity-score matching (1:2 nearest-neighbor) and subgroup analyses (age, sex, education) served as sensitivity analyses. Results Incident stroke occurred in 770 CHARLS (6.6%) and 347 ELSA (6.1%) participants. In fully adjusted models, stroke was associated with significantly faster cognitive decline in both cohorts (CHARLS: β = −0.068 points/year, 95% CI − 0.123 to − 0.013, p = 0.016; ELSA: β = −0.190, 95% CI − 0.229 to − 0.152, p < 0.001); after propensity-score matching, the ELSA association remained robust (β = −0.150, p < 0.001) while the CHARLS estimate was attenuated and no longer significant (β = −0.029, p = 0.386). The formal three-way interaction showed that higher family connection significantly attenuated stroke-related decline in ELSA ; the corresponding interaction for social support in CHARLS was directionally consistent but not significant (β = +0.082, 95% CI − 0.037 to 0.202, p = 0.177). Subgroup analyses showed a significant stroke-decline association across all age, sex, and education strata in ELSA, and only among male and less-educated participants in CHARLS. Conclusion Incident stroke was associated with faster cognitive decline in both a Chinese and an English cohort of middle-aged and older adults. A formal statistical test indicated that family connections significantly moderated this association in ELSA, whereas a similar but non-significant pattern was observed for social support in CHARLS. These associations warrant further investigation of social relationships as a potentially modifiable factor in post-stroke cognitive health; the observational design precludes causal conclusions.