LAUSR

Supplemental Digital Content is Available in the Text. Objective: To determine the incidence and nature of illness-related medical encounters (MEs) at a 90-km, ultramarathon, mass, community-based, endurance running event. Design: Retrospective, descriptive epidemiological study. Setting: Comrades Marathon (90 km), South Africa. Participants: One lakh three thousand one hundred thirty-one race starters over 6 years (2014-2019). Independent Variables: Incidence of moderate and serious/life-threatening MEs. Main Outcome Measures: All MEs were recorded by race medical doctors on race day each year. Medical encounters were recorded by severity, organ system, and final specific diagnosis (2019 consensus statement definition on mass community–based events). Incidences (I: per 1000 starters; 95% confidence intervals) were calculated for MEs. Results: There were 1971 illness-related MEs, with an overall incidence of 19.1 (range, 18.3-20.0). The incidence for serious/life-threatening MEs was 1.8 (range, 1.6-2.1). Incidences of MEs by organ systems affected were as follows: fluid/electrolyte (8.8; 8.3-9.4), central nervous system (4.0; 3.7-4.5), and gastrointestinal system (2.9; 2.6-3.2). Dehydration (I = 7.5: 7.0-8.1) and exercise-associated muscle cramping (I = 3.2: 2.9-3.6) were the 2 most common specific diagnoses. Conclusion: The incidence of MEs in the 90-km Comrades Marathon was one of the highest incidences of MEs reported in an endurance running event (1 in 52 starters and 1 in 556 starters for serious/life-threatening MEs). Preventative measures to reduce MEs are needed, and further investigations into the risk factors associated with MEs could assist in managing the risk and better prepare athletes, race organizers, and medical directors.