Household fuel use, social engagement, and cognitive decline in older Chinese adults: a prospective cohort study...

Solid fuel use remains a major source of indoor air pollution worldwide, and limited social engagement is increasingly recognized as a behavioral determinant of cognitive aging. However, evidence regarding their independent and combined effects on cognitive decline among older adults is scarce. This study aimed to evaluate the associations of household fuel use and social engagement with cognitive decline and to assess whether social engagement modifies the fuel-cognition relationship.

Data were drawn from 4,298 adults aged ≥ 60 years participating in the 2011-2020 waves of the China Health and Retirement Longitudinal Study (CHARLS). Household fuel use was measured at baseline and categorized into three types: clean fuels, coal, and biomass fuels. Social engagement was assessed at baseline based on participation in 11 types of social activities. Cognitive decline was defined as a ≥ 3-point reduction in global cognitive score from baseline at any follow-up wave. Cox proportional hazards models were fitted to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). Multiplicative interaction between fuel type and social engagement was tested by including cross-product terms.

During follow-up, 1,821 participants experienced cognitive decline. Compared with clean fuel use, coal use was associated with a significantly higher risk of cognitive decline (HR = 1.249, 95% CI: 1.061-1.470), whereas biomass fuel use was not (HR = 1.062, 95% CI: 0.944-1.194). Higher social engagement was consistently protective, with each additional activity associated with an 8.4% reduction in risk (HR = 0.916, 95% CI: 0.867-0.968). None of the interaction terms reached significance (coal × social engagement: HR = 0.977, 95% CI: 0.815-1.171), indicating no evidence that social engagement modifies the fuel-cognition association. Additional analyses showed that fuel use was not associated with follow-up cognitive scores (all p > 0.05), whereas social engagement remained positively associated with global cognition (β = 0.114, p = 0.006).

Coal use increases the risk of cognitive decline, whereas higher social engagement is protective; these influences operate independently without evidence of interaction. Reducing household reliance on coal while promoting meaningful social participation may represent complementary strategies to preserve cognitive health in aging populations.