Suggested novel risk factors for Swimming-Induced Pulmonary Edema - asthma and limited open water swimming experience.

Abstract

Swimming-induced pulmonary edema (SIPE) has gained increasing attention in recent years. However, risk factors for SIPE remain incompletely understood, and existing data are primarily based on small-scale studies. Which individual risk factors are associated with SIPE? We conducted a case-control study based on Sweden's largest open water swimming event, Vansbrosimningen. Data were obtained through interviews with individuals diagnosed with SIPE in 2017-2024 and through a web-based survey administered to controls without SIPE. Individual factors associated with SIPE were identified by multiple logistic regression. A total of 258 cases diagnosed with SIPE and 2117 controls were included. A first logistic regression model identified female sex (OR 5.3, 95% CI: 3.6-7.7), higher age (OR for ≥61 years 7.3, 95% CI: 3.8-14.2), hypertension (OR 1.9, 95% CI: 1.2-3.2), heart disease (OR 6.0, 95% CI: 2.5-14.2), asthma (OR 1.7, 95% CI: 1.2-2.6) and low frequency of open water swimming during the present season (OR for never: 3.6, 95% CI: 2.4-5.4) as independently associated with SIPE. A second model found that previous respiratory symptoms during open water swimming (OR: 3.5, 95% CI: 2.3-5.2) and acute respiratory tract infection (OR: 10.2, 95% CI: 5.2-20.2) were also strongly associated with SIPE, however the association with asthma failed statistical significance in this model. This study confirms previously reported individual risk factors for SIPE and immersion pulmonary edema - such as female sex, higher age, hypertension, heart disease, respiratory tract infection and prior SIPE episodes. In addition, our data suggests that asthma and limited experience of open water swimming are associated with an increased risk of SIPE. A comprehensive understanding of risk factors for SIPE will improve safety during open water swimming and contribute to the development of medical guidelines for SIPE.