Seasonality and territorial gradient of pulmonary embolism in France: an 8-year retrospective nationwide analysis

Introduction

Seasonality of Pulmonary Embolism (PE) is increasingly described, suggesting the negative impact of cold meteorological conditions. Yet, little is known about geographical and climatic impact. With various climates, and large regional temperature ranges, France provides a model for highlighting climate-related differences in PE prevalence. We thus made a whole country, 8-year retrospective analysis of PE prevalence, per season and geographical area, using standardized sex and age strata.

Methods

The French Hospital Discharge Database provided data on in-hospital-managed PE, with sex, age and geographical codes to calculate the standardized prevalence of PE (PE-SP) and map its geographical distribution. Climatic conditions were estimated taking average regional temperatures. Results: From 2012 to 2019, we identified 341,365 cases of PE (median age, 71y; 53.04 % female). PE-SP shows constant seasonality, with a higher incidence during the coldest months (globally +28.4 %), a peak in February and a trough in June (0.272 and 0.218 cases per 100,000 inhabitants respectively).

PE-SP also exhibits a marked territorial gradient, increasing from West to East and South to North, with a median magnitude of 86.9 %, (IQR 73.3 %–98.4 %, extreme values 50.1 %–133 %). This gradient remains whatever the sex or age, and over seasons and years. Finally, linear regression analysis, expressing PE-SP according to climatic conditions, found a significant association with TXQ10 (10th percentile of daily temperatures), highlighting higher PE-SP in geographical areas traditionally exposed to colder weather.

Conclusions

In France, PE occurrence is heterogeneously distributed, over seasons and also over territories. Geographical (seasonal and territorial) patient biotope should be considered regarding the thrombotic risk.