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 (PM2.5)] 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 PM2.5 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 PM2.5 was 32.7 [range 24.4–38.2] µg/m3, and 60% used biomass. After confounder adjustment, we observed positive associations between within-village variation in PM2.5 and CIMT in all participants [1.79%, 95% confidence interval (CI), −0.31 to 3.90 per 1 µg/m3 of PM2.5] and in men (2.98%, 95% CI, 0.23–5.72, per 1 µg/m3 of PM2.5). 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 PM2.5 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.This work was supported by the European Research Council (Grant Agreement 336167 for the CHAI Project) and the Wellcome Trust (Grant: 084674/Z for the third follow-up of the APCAPS). C.T. was funded through a Ramón y Cajal fellowship (RYC-2015–17402) awarded by the Spanish Ministry of Economy and Competitiveness