The association between physical activity and cardiovascular disease under indoor air pollution among middle-aged-to-elderly people: a sex-specific analysis from CHARLS

The associations between physical activity (PA) and outdoor air pollution with cardiovascular disease (CVD) are well established, but evidence regarding indoor air pollution remains scarce. This study examined sex-specific associations between PA and CVD in the context of indoor air pollution resulting from solid fuel use. This nationwide cross-sectional study analyzed data from 18,640 middle-aged and older adults from the 2018 wave of the China Health and Retirement Longitudinal Study. PA was measured using the International Physical Activity Questionnaire. Information on solid fuel use was obtained through self-reported primary sources of cooking and heating fuels. CVD was defined based on self-reported physician diagnoses of heart diseases or stroke. Participants with higher PA levels exhibited a lower CVD prevalence, whereas all types of solid fuel use were associated with higher prevalence, with the highest prevalence observed among mixed solid fuel users. Physically inactive individuals generally exhibited the highest prevalence across all fuel-use groups. Exposure-response analyses revealed that PA was inversely associated with CVD prevalence among male users of clean energy, coal, and crop residue/wood burning, and among female users of clean energy and crop residue/wood burning (all P for overall < 0.05). Among males, PA significantly mediated the relationship between solid fuel use and CVD, with opposing statistical mediation directions observed for coal (5.07%) and crop/wood (–18.99%). In females, significant statistical mediation was observed only for crop/wood use (-16.89%). This cross-sectional study suggests that the inverse association between PA and CVD prevalence may vary by sex and solid fuel type. PA was associated with lower CVD prevalence across all fuel types in males, but only among females using clean energy and crop residue/wood burning. These findings highlight the need for targeted health policies for older adults undergoing energy transition.