Background There is a high incidence of medical encounters (MEs) in ultramarathon road running races but risk factors associated with MEs in events have not been well investigated.

Objective To determine the independent risk factors for all medical encounters in a 90km ultramarathon running race.

Design Retrospective clinical audit, cross-sectional analysis

Setting 2014–2018 Comrades ultramarathon (90 km, alternating annually between an ‘up’ vs. a ‘down’ run between a coastal and inland city), South Africa

Participants 70328 race starters

Interventions All participants voluntarily completed two medical-related questions (history of allergies and/or a medical condition/or use medication) upon entry for the event. Race day data, including ‘up’ vs. ‘down’ run, start time, finish time, age and sex of starters, was recorded by the race organisers. MEs were recorded by medical staff during and immediately after the event.

Main Outcome Measures Independent risk factors associated with all MEs (both injury- and illness-related) using race day factors and individual self-reported medical history (allergies and medical conditions/medication use) were investigated using a multivariate model with a Poisson distribution, reporting the prevalence ratio (PR: 95% CI).

Results Over 5 years 1 749 medical encounters were recorded. Independent risk factors associated with all MEs were: older females (males 31–40years vs females>50 years, 0.6: 0.4–0.8, p=0.0017; males 41–50 years vs females>50 years, 0.5: 0.4–0.7, p=0.0002; males >50 years vs females >50 years, 0.6: 0.4–0.8, p=0.0008), slower race pace (7-<8 min/km vs 8-<9 min/km, 0.8: 0.7–0.9; p=0.0044) and self-reported medical conditions/medication use (no history vs. medical condition/medication use, 0.7: 0.6–0.9; p=0.0082).

Conclusion A self-reported history of a medical condition/medication, older females, and slower runners were risk factors associated with MEs during/immediately after the 90km Comrades ultramarathon. These data support initiatives to introduce pre-race medical screening, which could then form the basis for the design and implementation of prevention programs to manage risk of MEs at these events.