Long-term exposure to air pollution, road traffic noise and greenness, and incidence of myocardial infarction in women

Abstract

Background: Emerging evidence shows that long-term exposure to air pollution, road traffic noise, and greenness can each be associated with cardiovascular disease, but only few studies combined these exposures. In this study, we assessed associations of multiple environmental exposures and incidence of myocardial infarction using annual time-varying predictors.

Materials and methods: In a population-based cohort of 20,407 women in Sweden, we estimated a five-year moving average of residential exposure to air pollution (PM_2.5, PM₁₀ and NO₂), road traffic noise (L_den), and greenness (normalized difference vegetation index, NDVI in 500 m buffers), from 1998 to 2017 based on annually varying exposures and address history. We used adjusted time-varying Cox proportional hazards regressions to estimate hazard ratios (HR) and 95 % confidence intervals (95 % CI) of myocardial infarction per interquartile range (IQR). Furthermore, we investigated interactions between the exposures and explored potential vulnerable subgroups.

Results: In multi-exposure models, long-term exposure to greenness was inversely associated with incidence of myocardial infarction (HR 0.89; 95 % CI 0.80, 0.99 per IQR NDVI increase). Stronger associations were observed in some subgroups, e.g. among women with low attained education and in overweight (BMI ≥ 25 kg/m²) compared to their counterparts. For air pollution, we observed a tendency of an increased risk of myocardial infarction in relation to PM_2.5 (HR 1.07; 95 % CI 0.93, 1.23) and the association appeared stronger in women with low attained education (HR 1.30; 95 % CI 1.06, 1.58). No associations were observed for PM₁₀, NO₂ or road traffic noise. Furthermore, there were no clear interaction patterns between the exposures.

Conclusion: Over a 20-year follow-up period, in multi-exposure models, we found an inverse association between residential greenness and risk of myocardial infarction among women. Furthermore, we observed an increased risk of myocardial infarction in relation to PM_2.5 among women with low attained education. Road traffic noise was not associated with myocardial infarction.

Keywords: Air pollution; Cardiovascular disease; Cohort study; Greenness; Multiple exposures; Road traffic noise.