To Örebro University

BACKGROUND: Swimming-induced pulmonary edema (SIPE) has been reported to subside within 24-48 hours, but comprehensive follow-up studies on symptom duration and long-term effects are missing.

RESEARCH QUESTION: What is the symptom duration, recurrence, and long-term effects of SIPE?

STUDY DESIGN AND METHODS: A follow-up study was conducted based on 165 cases of SIPE from Sweden's largest open water swimming event with 26,125 individuals participating during 2017-2019. Data on patient characteristics, clinical findings and symptoms were collected upon admission. Telephone interviews at 10 days and 30 months were performed to explore symptom duration, recurrence of SIPE symptoms, need of medical evaluation and long-term effects of self-assessed general health and physical activity level.

RESULTS: Follow-up at 10 days was performed for 132 cases and at 30 months for 152 cases. Most of the cases were women and mean age was 48 years. At the 10-day follow-up, symptom duration >2 days after the swimming race were reported by 38%. The most common symptoms were dyspnea and cough. In patients followed for 30 months, recurrence of respiratory symptoms during open water swimming was reported by 28%. In multivariable logistic regression, asthma was independently associated with both symptom duration >2 days and recurrence of SIPE symptoms (p =0.045 and p =0.022 respectively). Most participants reported equal or improved general health (93%) and physical activity level (85%) after experiencing SIPE, but 58% had not swum in open water since the event.

INTERPRETATION: The present large cohort study challenges the established hallmark of SIPE symptom duration of <48 hours, while SIPE recurrence was in the previously reported range. At 30 months, most patients reported unchanged self-assessed general health and physical activity level. These findings add to our understanding of the course of SIPE and can provide evidence-based information to swimmers and health care professionals.