Keywords: heat stroke, marathon (PubMed Search)
Exertional Heat Stroke at the Boston Marathon
Study goal: To assess for possible associations between exertional heat stroke (EHS) and sex, age, prior performance and environmental conditions
Data sourced from 2015-2019 Boston Marathon races.
Why Boston: The Boston marathon is one of the only marathons that require qualifying times for entry for a majority of runners which yields a high proportion of faster than average runners. The race is frequently characterized by extreme weather conditions, including warm and humid days.
Results: 136,161 race starters. Incidence of EHS was 3.7 cases per 10,000 starters.
Note: Twin Cities Marathon found 3 cases per 10,000 runners.
Mean age of runners was 43.3. Female 45%, male 55%.
Significant associations between sex and age, sex and start wave and age group and start wave.
Sex not associated with increased EHS incidence.
Age < 30 and assignment to the first 2 waves (faster runners) was significantly associated with increased EHS.
All cases of EHS occurred with average wet bulb globe temperatures (WBGT) were 17° – 20° C.
Linear correlation between EHS and incidence in addition to increases in WBGT from start to peak.
72.5% of cases were race finishers. Non finishers presented after mile 18.
Almost 30% developed post treatment hypothermia.
Almost 2/3rds were discharged directly, the remainder required hospital transport.
Authors estimate needing at least 4 ice water immersion tubs per 10,000 runners with potential of needing 8-10 if race day is humid.
Conclusions: Overall, EHS represented a small percentage of medical encounters but required significant resources.
Younger and faster runners are at high risk of EHS.
Greater increases in heat stress from start to peak worsens risk.
Definitions: WGBT - The Wet Bulb Globe Temperature (WBGT) is a measure of the heat stress in direct sunlight, which takes into account: ambient temperature, relative humidity, wind speed, sun angle and cloud cover (solar radiation). This differs from the heat index, which takes into consideration temperature and humidity and is calculated for shady areas.
Breslow RG, Collins JE, Troyanos C, Cohen MC, D'Hemecourt P, Dyer KS, Baggish A. Exertional Heat Stroke at the Boston Marathon: Demographics and the Environment. Med Sci Sports Exerc. 2021 Sep 1;53(9):1818-1825.