Association between ambient and household air pollution with carotid intima-media thickness in peri-urban South India: CHAI-Project

BACKGROUND: Evidence linking ambient air pollution with atherosclerosis is lacking from low- and middle-income countries. Additionally, evidence regarding the association between household air pollution and atherosclerosis is limited. We evaluated the association between ambient fine particulate matter [particulate matter with an aerodynamic diameter of ≤2.5 µm (PM(2.5))] and biomass fuel use on carotid intima-media thickness (CIMT), a surrogate of atherosclerosis, in India. METHODS: We analysed the third follow-up of the Andhra Pradesh Children and Parent Study cohort (2010–2012), which recruited participants from 28 peri-urban villages. Our primary outcome was mean CIMT, measured using a standardized protocol. We estimated annual average PM(2.5) outdoors at residence using land-use regression. Biomass cooking fuel was self-reported. We fitted a within-between linear-mixed model adjusting for potential confounders. RESULTS: Among 3278 participants (48% women, mean age 38 years), mean PM(2.5) was 32.7 [range 24.4–38.2] µg/m(3), and 60% used biomass. After confounder adjustment, we observed positive associations between within-village variation in PM(2.5) and CIMT in all participants [1.79%, 95% confidence interval (CI), −0.31 to 3.90 per 1 µg/m(3) of PM(2.5)] and in men (2.98%, 95% CI, 0.23–5.72, per 1 µg/m(3) of PM(2.5)). Use of biomass cooking fuel was associated with CIMT in all participants (1.60%, 95% CI, −0.46 to 3.65), especially in women with an unvented stove (6.14%, 95% CI, 1.40–10.89). The point-estimate for the PM(2.5) association was larger in sub-groups with higher cardiometabolic risk profile. CONCLUSIONS: Ambient and household air pollution were positively associated with CIMT in a peri-urban population of India, although with limited precision for some estimates. We observed differences in the association between ambient and household air pollution and CIMT by gender.