Long‐Term Exposure to Ambient PM _2.5 and Hospitalizations for Myocardial Infarction Among US Residents: A Difference‐in‐Differences Analysis

Abstract

Background Air pollution has been recognized as an untraditional risk factor for myocardial infarction (MI). However, the MI risk attributable to long‐term exposure to fine particulate matter ≤2.5 μm in aerodynamic diameter (PM 2.5 ) is unclear, especially in younger populations, and few studies have represented the general population or had power to examine comorbidities. Methods and Results We applied the difference‐in‐differences approach to estimate the relationship between annual PM 2.5 exposure and hospitalizations for MI among US residents and further identified potential susceptible subpopulations. All hospital admissions for MI in 10 US states over the period 2002 to 2016 were obtained from the Healthcare Cost and Utilization Project State Inpatient Database. In total, 1 914 684 MI hospital admissions from 8106 zip codes were included in this study. We observed a 1.35% (95% CI, 1.11–1.59) increase in MI hospitalization rate for 1‐μg/m 3 increase in annual PM 2.5 exposure. The estimate was robust to adjustment for surface pressure, relative humidity, and copollutants. In the population exposed to ≤12 μg/m 3 , there was a larger increment of 2.17% (95% CI, 1.79–2.56) in hospitalization rate associated with 1‐μg/m 3 increase in PM 2.5 . Young people (0–34 years of age) and elderly people (≥75 years of age) were the 2 most susceptible age groups. Residents living in more densely populated or poorer areas and individuals with comorbidities were observed to be at a greater risk. Conclusions This study indicates long‐term residential exposure to PM 2.5 could increase risk of MI among the general US population, people with comorbidities, and poorer individuals. The association persists below current standards.

Long-Term Exposure to Air Pollution Below Regulatory Standards and Cardiovascular Diseases Among US Medicare Beneficiaries: A Double Negative Control Approach

“…Similarly, Brunekreef et al 15 observed steeper slopes at low exposures to PM 2.5 below 15 µg/m 3 and NO 2 below 40 µg/m 3 in the supralinear associations for stroke incidence, based on data from 22 European cohorts in the European Study of Cohorts for Air Pollution Effects Project. Several previous studies of the Medicare population have found a greater risk of a range of cardiovascular outcomes when restricted to lower exposures 9,13,14,27 . Our main nding adds to epidemiologic evidence of potential population-level health concerns at pollution levels conventionally considered safe and provides some assurance that the associations are not biased by unmeasured confounding.…”

“…Previous studies found the shape of the exposure-response curves for long-term PM 2.5 and all-cause and cardiovascular mortality to be curvilinear with no evidence of a threshold 11,12 . According to several studies of large cohorts in the US 9,13,14 and Europe 15,16 , the risk of cardiovascular diseases could persist and even become stronger at lower exposure levels below the annual limit values set by the US Environmental Protection Agency (EPA) and European Union (EU). The suggested higher incremental risk in relation to a lower air pollutant level raises the question of whether the national and international air quality guidelines are protective enough.…”

Long-Term Exposure to PM10 Air Pollution Exaggerates Progression of Coronary Artery Disease

“…Air pollutants are composed of particulate matter (PM), including coarse particles, characterized by being 10 micrometers or less to 2.5 micrones in size (PM10); fine particles, defined as being 2.5 micrones or less in diameter (PM2.5); and ultrafine particles and gaseous pollutants, such as nitrogen dioxide and ozone. The inhalation of PM2.5 generated by the combustion of fossil fuels is considered as one of the non-traditional risk factors for coronary artery disease [1].…”