Long-term air pollution exposure and the incidence of cardiovascular diseases among American elderly population

Background & Aim: Numerous studies have linked PM2.5, NO2, and ozone with cardiovascular diseases. Fewer studies have examined the multi-pollutant effects and effects at low pollutant levels, as well as potential effect modifications. Methods: Our study population included all Medicare enrollees continuously enrolled in the fee-for-service (FFS) program and both Medicare part A and part B in the contiguous U.S. from 2000 to 2016. We looked at the association between population-weighted ZIP code level annual average PM2.5, NO2, and warm-season ozone (May-October) and the first diagnosis of atrial fibrillation (AF), congestive heart failure (CHF), and stroke using Cox proportional hazards models. We adjusted for individual demographic characteristics and area-level covariates. We further examined these associations at low pollutant levels (PM2.5: <10 μg/m3¬, <8 μg/m3; NO2: <25 ppb, <18 ppb; warm-season ozone: <50 ppb, <40 ppb) and potential modifications by race and comorbidities (diabetes, hypertension, hyperlipidemia). Results: In the full cohorts, elevated PM2.5 and NO2 levels were associated with increased incidence of AF, CHF, and stroke. For each μg/m3 increase in annual PM2.5, HRs were 1.0059 (95%CI: 1.0054, 1.0064), 1.0260 (95%CI: 1.0256, 1.0264), and 1.0279 (95%CI: 1.0274, 1.0284), respectively. For each ppb increase in annual NO2, HRs were 1.0057 (95%CI: 1.0056, 1.0059), 1.0112 (95%CI: 1.0110, 1.0113), and 1.0095 (95%CI: 1.0093, 1.0096), respectively. Each one ppb increase in warm-season ozone was associated with an increased risk of CHF (HR=1.0035, 95%CI: 1.0033-1.0037) and stroke (HR=1.0026, 95%CI: 1.0023-1.0028). The effect estimates were stronger when we restricted the analyses to low pollutant levels. We also found generally higher risks for enrollees who are black or have diabetes. Conclusions: Long-term exposure to PM2.5, NO2, and warm-season ozone were associated with risks of cardiovascular diseases, even at low pollutant levels. These associations were modified by race and several comorbidities. Keywords: Air Pollution, PM2.5, NO2, Ozone, Cardiovascular Diseases