[Association of air-pollution with acute myocardial infarction: A case-crossover study]

A large number of studies have demonstrated an association between ambient air pollutant exposures and acute myocardial infarctions (AMI). Case-crossover methods are frequently used for analyzing the acute health effects of air pollution. Nevertheless, only a few studies controlled for potential confounders like other air pollutants and temperature.

The defined geographic entity for the collection of acute myocardial infarctions was composed of 15 municipalities in Charleroi. Charleroi is a relatively highly polluted region in Wallonia, the South of Belgium. The analyses presented hereafter concern patients in the 25-74 years age range over time from 1999 to 2009. Ambient concentrations of PM10, O3, NO2, CO and temperature were available from stationary monitors during this time period. A time-stratified case-crossover approach was applied. Season stratified analysis and analysis matching for environmental confounders were also performed.

A total of 3303 AMIs were analyzed during the study period. For the entire year, O3 was significantly associated with AMI, OR=1.028 (CI95%: 1.003-1.054). The highest associations (for a 10 μg.m(-3) rise in pollutant levels) between air pollution and myocardial infarction were observed for PM10 and O3 during the warm period, OR=1.086 (CI95%: 1.020-1.151) and 1.064 (CI95%: 1.024-1.105), respectively. Matching cases and controls for temperature produced weaker association between O3 and AMI (OR=1.003, CI95%: 0.974-1.032). In contrast, this matching had no effect on the association between PM10 and AMI. The adjustment for NO2 concentration decreased the association between PM10 and AMI.

The results of this study reinforce the evidence of the short-term effects of air pollution on acute myocardial infarction, especially during the warm season. This also suggests that the case-crossover method is a suitable tool in studying the association between acute events and air pollution. Controlling for potential environmental confounding effects is also feasible with this method.