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 2006-2009 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 µM (PM10) and less than 2.5 µM (PM(2.5)), 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°C decrease in temperature (adjusted incidence risk ratio (IRR) 0.92, 95% CI 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% CI 0.78 -0.95). There was a trend for an incremental risk of STEMI for each 10 µg/m³ PM(2.5) increase and during influenza epidemics with IRR of 1.02 (95% CI 1.00-1.04) and 1.07 (95% CI 0.98-1.16), respectively. CONCLUSION: In a global environmental model, low temperature is the most important environmental trigger for STEMI, whereas air pollution and influenza epidemics only seem to have a modest effect.