Longitudinal associations between household solid fuel use and depression in middle-aged and older Chinese population: A cohort study

Background: Previous studies found that ambient air pollution was associated with a higher prevalence of depressive symptoms. However, the longitudinal associations between household solid fuel use, which is the main source of household air pollution, and depressive symptoms remain unclear. This cohort study aimed to explore the associations between household solid fuel use and incidence of depressive symptoms in China. Methods: In total, 8637 participants were enrolled in this prospective cohort study. Depressive symptoms were assessed using the 10-item Center for Epidemiological Studies Depression Scale. The associations between baseline household solid fuel use and the incidence of depressive symptoms were examined using Cox proportional hazards regression models. Results: During the 4-year of follow-up, 2074 of 8637 participants developed depressive symptoms. Compared with participants who used clean fuel for both heating and cooking, the multivariate-adjusted hazard ratio (HR) (95% confidence intervals [95% CI]) for depressive symptoms incidence in participants who used solid fuels for two purposes (cooking and heating) was 1.15 (1.01, 1.31). In the solid fuel use subgroup analysis, use of solid fuels for cooking (HR, 1.12; 95% CI, 1.02-1.24) was associated with a higher incidence of depressive symptoms after adjustments while use for heating (HR, 1.05; 95% CI, 0.93-1.18) was not. Moreover, compared with persistent solid fuel users, switching from solid to clean fuels for cooking resulted in a lower risk of depressive symptoms before adjustments (HR, 0.82; 95% CI, 0.71-0.95) and a non-significant association (HR, 0.90; 95% CI, 0.77-1.04) afterwards. Conclusions: The results suggest that household solid fuel use for cooking was associated with a higher incidence of depressive symptoms. Preventive strategies based on improving household cooking environment for depressive symptoms should be established.