Extreme weather conditions as a gender-specific risk factor for acute myocardial infarction.

Background: Acute coronary syndrome is a disease with high prevalence and high mortality. Exposure to heat or cold increases the risks of myocardial infarction significantly. Gender-specific effects of this have not yet been examined. Our goal was to determine whether extreme weather conditions, which become more and more frequent, are gender-specific risk factors for myocardial infarction, in order to help provide faster diagnosis and revascularization therapy for patients.

Methods: We analysed the incidence of ST-elevation myocardial infarction (STEMI) in a large urban area over a 65-months period in a cohort study. A day was the unit of analysis. Incidence rate ratios (IRR) with Poisson regression models were calculated. All patients with STEMI on Saturdays and Sundays were included. Gender, high or low perceived temperatures (PT), a function of temperature, wind speed and humidity, and meteorological cold and heat warnings by the Austrian Central Institute for Meteorology and Geodynamics (ZAMG) were considered as risk factors.

Results: During the 562 days of the study period, a total of 1109 patients with STEMI (803; 72% men, mean age 61;14 years) were included. The gender difference between men and women was much more pronounced on cold (0 °C) days (85% of patients male; 1.8 per day) than on hot (20 °C) days (71% male; 1.4 per day) or days without extreme temperatures (72% male; 1.4 per day). We found significant interaction between gender and cold days (IRR of the interaction term 2.3 (95% CI 1.2-4.6), p = 0.02). No gender-specific effect was observed on warm days (IRR for interaction 0.9 (95% CI 0.6-1.3), p = 0.3).

Conclusion: Low perceived temperature pronouncedly increases the already elevated risk for STEMI in males. Whether this effect is based on gender alone, or on one of the cardiovascular risk factors which are more common in men, is up to further study.