Out-of-Hospital Cardiac Arrest and Airborne Fine Particulate Matter: A Case–Crossover Analysis of Emergency Medical Services Data in Indianapolis, Indiana

Abstract

BackgroundPrevious studies have found particulate matter (PM) < 2.5 μm in aerodynamic diameter (PM2.5) associated with heart disease mortality. Although rapid effects of PM2.5 exposure on the cardiovascular system have been proposed, few studies have investigated the effect of short-term exposures on out-of-hospital cardiac arrest (OHCA).ObjectivesWe aimed to determine whether short-term PM2.5 exposures increased the risk of OHCA and whether risk depended on subject characteristics or presenting heart rhythm.MethodsA case–crossover analysis determined hazard ratios (HRs) for OHCAs logged by emergency medical systems (EMS) versus hourly and daily PM2.5 exposures at the time of the OHCA and for daily and hourly periods before it.ResultsFor all OHCAs (n = 1,374), exposures on the day of the arrest or 1–3 days before arrest had no significant effect on the incidence of OHCA. For cardiac arrests witnessed by bystanders (n = 511), OHCA risk significantly increased with PM2.5 exposure during the hour of the arrest (HR for a 10-μg/m3 increase in PM2.5 exposure = 1.12; 95% confidence interval, 1.01–1.25). For the subsets of subjects who were white, 60–75 years of age, or presented with asystole, OHCA risk significantly increased with PM2.5 during the hour of the arrest (HRs for a 10-μg/m3 increase in PM2.5 = 1.18, 1.25, or 1.22, respectively; p < 0.05). HR generally decreased as the time lag between PM2.5 exposure and OHCA increased.ConclusionThe results suggest an acute effect of short-term PM2.5 exposure in precipitating OHCAs, and a need to investigate further the role of subject factors in the effects of PM on the risk of OHCA.

Effects of Fine Particulate Matter on Daily Mortality for Specific Heart Diseases in Japan

“…For sudden cardiac death, Rosenthal et al found an association between PM2.5 exposure and out-ofhospital cardiac arrests in Indiana. 21 On the other hand, Levy et al did not observe an association between PM10 and out-of-hospital primary cardiac arrest in Seattle and Washington. 22 In Japan, most of the research interest involving air pollutant epidemiology has focused on impacts on the respiratory system and we are aware of only a few reports that examined the association between air pollutants and cardiovascular disease.…”

A Case-Crossover Analysis of Out-of-Hospital Cardiac Arrest and Air Pollution

“…The case-crossover design was first introduced by Maclure 24 and is used increasingly in the literature to assess episodic events following short-term exposure to air pollution. 3,4,[7][8][9][10]25 In the case-crossover design, each individual experiencing a health event serves as his or her own reference; in other words, individuals act as their own control. Ambient air pollution is used as a proxy for personal exposure.…”

“…Epidemiological studies have found the time to trigger a cardiac event from exposure to PM 2.5 or ozone ranges from the day or previous day of onset to hours before onset. 4,7,9,10 Part of this inconsistent range of time to trigger is due to exposure time misclassification. This could be better handled by addressing the uncertainty in combining the disparate data sets such as OHCA recorded at the minute and continuous across space and air pollution data recorded hourly at fixed locations.…”

Particulate Matter Air Pollution and Cardiovascular Disease

“…129 -136 However, no clear pollution-related associations were observed in studies from a relatively clean metropolitan area, Vancouver, British Columbia, Canada, 137,138 or from a relatively large study in Atlanta, Ga. 139 Similarly, pollution-related associations have been observed with cardiac arrest in Rome, Italy, 140 and Indianapolis, Ind, 141 but not in Seattle, Wash. 142,143 The mixed results may reflect different PM compositions due to different sources or variations among the methods used.…”