Association between solid fuel use and cognitive impairment: A cross-sectional and follow-up study in a middle-aged and older Chinese population

BACKGROUND: To date, few studies have focused on the influence of indoor air pollution on cognitive impairment. Thus, we aimed to explore the association of household fuel use, the major cause of household air pollution, with cognitive functioning among a sample of middle-aged and older Chinese individuals. METHODS: A total of 10,372 and 8,397 participants from the China Health and Retirement Longitudinal Study (CHARLS) were enrolled in the cross-sectional and follow-up analyses, respectively. Cognitive functioning was evaluated via a structured questionnaire in three dimensions: orientation and attention, episodic memory, and visuo-construction. The associations between household solid fuel use (for cooking and heating) and cognitive functioning were elucidated by generalized linear models. Furthermore, we explored the combined effect of solid fuel use in cooking and heating and examined the effects of switching cooking fuel types on a 4-year change in cognitive functioning. RESULTS: In the cross-sectional study, solid fuel use for cooking or heating, separately or simultaneously, was positively associated with cognitive impairment, after adjusting for potential confounders. Similarly, in the follow-up study, solid cooking fuel use was associated with a greater decline in cognitive score overall (β = -0.24, 95% confidence interval [CI]: -0.45, -0.04), mostly in the episodic memory (β = -0.19, 95% CI: -0.34, -0.03) and visuo-construction (β = -0.03, 95% CI: -0.05, -0.01) dimensions; solid heating fuel use was associated only with a greater decrease in the orientation and attention dimension (β = -0.13, 95% CI: -0.25, -0.01). A combined effect of household fuel use was also observed (P < 0.05). Moreover, subjects who switched from solid to cleaner cooking fuel displayed a significantly lower degree of cognitive decline for all dimensions than did persistent solid fuel users over a 4-year period (P < 0.05). CONCLUSION: Our findings show that household solid fuel use is a risk factor for the development of cognitive impairment. Improving the structure of cooking fuel may therefore have great public health value for the prevention of cognitive impairment.