Short-term air pollution exposure is a risk factor for acute coronary syndromes in an urban area with low annual pollution rates: Results from a retrospective observational study (2011–2015)

Abstract

Epidemiological data suggest that air pollutants are risk factors for cardiovascular disease. Recent studies have questioned the adequacy of current legal pollutant limits, because concentrations lower than those recommended still affect cardiovascular morbidity and mortality. To investigate the association between short-term exposure to air pollutants and the daily diagnosis of acute coronary syndrome (ACS) at the emergency department (ED) of S. Croce Hospital (Cuneo, Italy), between 2011 and 2015. We evaluated the effect of particulate matter (PM2.5-10), nitrogen dioxide and ozone as primary exposure, together with temperature and relative humidity as climatological control variables, on ED admissions for ACS (response variables). We studied residents aged ≥35 years, classified into three age groups (35-64, 65-74 and ≥75 years). Environmental data were analysed according to Poisson's regression, and conventional cardiovascular risk factors (CRFs; hypertension, diabetes, coronary artery disease, smoking and dyslipidaemia) were included as control variables. ED admissions for ACS were 1625/391,689, with 298 in 2011 (0.183%), 305 in 2012 (0.188%), 347 in 2013 (0.214%), 341 in 2014 (0.21%) and 334 in 2015 (0.206%), with a general growth rate of 2.08% (from 2011 to 2015). The CRFs examined were confirmed to be highly associated with occurrence of ACS. Our study identified PM2.5 and temperature in all age groups to be additional risk factors, with PM2.5 exposure (P<0.01) being a particular risk for those aged ≥75 years. Dose-response models confirmed only PM2.5 as the main environmental risk factor in elderly patients (relative risk 1.06, 95% confidence interval 1.02-1.11; lag time 0-3 days). We also found a consistent relative risk for temperature in all age groups. This study confirms the importance of PM2.5 as a risk factor for ACS, mostly in elderly patients, even in a city with low annual pollution rates.