Environmental triggers of acute myocardial infarction: results of a nationwide multiple-factorial population study

Objective The objective of this study was to study the independent environmental triggers of ST-elevation myocardial infarction (STEMI) in a multifactorial environmental population model. Methods and results Daily counts of all STEMI patients who underwent urgent percutaneous coronary intervention over the period 20062009 in Belgium were associated with average daily meteorological data and influenza-like illness incidence data. The following meteorological measures were investigated: particulate matter less than 10 mu M (PM10) and less than 2.5 pM (PM2.5), ozone, black smoke, temperature and relative humidity. During the study period a total of 15,964 STEMI patients (mean age 63,75% male) were admitted with a daily average admission rate of 11 +/- 4 patients. A multivariate Poisson regression analysis showed that only the temperature was significantly correlated with STEMI, with an 8% increase in the risk of STEMI for each 10 degrees C decrease in temperature (adjusted incidence risk ratio (IRR) 0.92,95% Cl 0.89-0.96). The effects of temperature were consistent among several subpopulations but the strongest effect was seen in diabetic patients (IRR 0.85, 95% Cl 0.78 -0.95). There was a trend for an incremental risk of STEMI for each 10 mu g/m(3) PM2.5 increase and during influenza epidemics with IRR of 1.02 (95% CI 1.00-1.04) and 1.07 (95% Cl 0.98-1.16), respectively. Conclusion In a global environmental model, low temperature is the most important environmental trigger for STEM!, whereas air pollution and influenza epidemics only seem to have a modest effect.