Sex-specific differences regarding seasonal variations of incidence and mortality in patients with myocardial infarction in Germany.

BACKGROUND: Seasonal variation regarding the incidence and the short-term mortality of acute myocardial infarction (MI) was frequently reported, but data about sex-specific differences are sparse.

METHODS: We analysed the impact of seasons and temperature on incidence and in-hospital mortality of patients with acute MI in Germany between 2005 and 2015.

RESULTS: The nationwide sample comprised 3,008,188 hospitalizations of MI patients (2005-2015). The incidence was 334.7/100,000 citizens/year. Incidence inclined from 316.3 to 341.6/100,000 citizens/year (β 0.17 [0.10 to 0.24], P < 0.001), while in-hospital mortality rate decreased from 14.1% to 11.3% (β -0.29 [-0.30 to -0.28], P < 0.001). Overall, 377,028 (12.5%) patients died in-hospital. Seasonal variation of both incidence and in-hospital mortality was of substantial magnitude. Seasonal incidence (86.1 vs. 79.0/100,000 citizens/year, P < 0.001) and in-hospital mortality (13.2% vs. 12.1%, P < 0.001) were higher in winter than in summer. Risk to die in winter was elevated (OR 1.080 (95% CI 1.069-1.091), P < 0.001) compared to summer season independently of sex, age and comorbidities. Reperfusion treatment with drug eluting stents and coronary artery bypass graft were more often used in summer. We observed sex-specific differences regarding the seasonal variation of in-hospital mortality: males showed lowest mortality in summer, while females during fall. Low temperature dependency of mortality seems more pronounced in males.

CONCLUSION: Incidence of acute MI increased 2005-2015, while in-hospital mortality rate decreased. Seasonal variation of incidence and in-hospital mortality were of substantial magnitude with lowest incidence and lowest mortality in the summer season. Additionally, we observed sex-specific differences regarding the seasonal variation of the in-hospital mortality.