A Case-Crossover Analysis of Out-of-Hospital Cardiac Arrest and Air Pollution
Background—Evidence of association between exposure to air pollution and overall cardiovascular morbidity and mortality is increasingly found in the literature. However, results from studies of the association between acute air pollution exposure and risk of out-of-hospital cardiac arrest (OHCA) are inconsistent for fine particulate matter (PM2.5), and while pathophysiological evidence indicates a plausible link between OHCA and ozone, none has been reported. Approximately 300,000 persons in the U.S. experience an OHCA each year of which over 90% die. Understanding the association provides important information to protect public health.
Methods and Results—The association between OHCA and air pollution concentrations hours/days before onset was assessed using time-stratified case-crossover design using 11,677 emergency medical service logged OHCA events between 2004-2011 in Houston, Texas. Air pollution concentrations were obtained from an extensive area monitor network. An average increase of 6 µg/m3 in PM2.5 2 days before onset was associated with an increased risk of OHCA (1.046; 95% CI 1.012 to 1.082). A 20 ppb ozone increase for the eight-hour average daily maximum was associated with an increased risk of OHCA on the day of the event (1.039; 95% CI 1.005 to 1.073). Each 20 ppb increase in ozone in the previous 1 to 3 hours was associated with an increased risk of OHCA (1.044; 95% CI 1.004 to 1.085). Relative risk estimates were higher for men, African Americans or those aged over 65.
Conclusions—The findings confirm the link between OHCA and PM2.5 and introduce evidence of a similar link with ozone.
- Received August 8, 2012.
- Accepted January 30, 2013.
- Copyright © 2013, Circulation