Sex-specific and age-related seasonal variations regarding incidence and in-hospital mortality of pulmonary embolism in Germany

Background: Studies have reported seasonal variations regarding the incidence and the short-term mortality of pulmonary embolism (PE). The aim of this study was to identify sex-specific and age-related differences in seasonal patterns regarding hospitalisations and mortality of PE patients. Methods: We analysed the impact of seasons on incidence and in-hospital mortality of male and female hospitalised PE patients in Germany (2005-2015) based on the German nationwide inpatient sample. Results: The German nationwide inpatient sample comprised 885806 hospitalisations due to PE (2005-2015). Seasonal variations of both incidence (p=0.021) and in-hospital mortality (p<0.001) were of significant magnitude. Quarterly annual incidence (25.5 versus 23.7 of 100000 citizens per year, p=0.021) and in-hospital mortality (17.0% versus 16.7%, p=0.008) were higher in winter than in summer. Risk of in-hospital mortality in winter was slightly higher (OR 1.03 (95% CI 1.01-1.06), p=0.015) compared to summer, independently of sex, age and comorbidities. Additionally, we observed sex-specific differences during seasons: the highest number of hospitalisations of PE patients of both sexes was during winter, whereas the nadir of male patients was in spring and that of female patients was in summer. Both sexes showed a maximum of in-hospital mortality in spring. Seasonal variation regarding incidence and mortality was pronounced in older patients. Conclusion: Incidence and the in-hospital mortality of PE patients showed a significant seasonal variation with sex-specific differences. Although it has to be hypothesised that the seasonal variation of PE is multifactorially dependent, variation in each season was not explained by seasonal differences regarding age, sex and the prevalence of important comorbidities.