Epidemiology of Exertional
Heat Illness Among U.S. High School Athletes

Kerr ZY,
Casa DJ, Marshall SW, Comstock D. Am J Prev Med 2013 Jan 44(1)

It has been estimated that over 9000 high
school athletes are treated annually for exertional heat illness (EHI). There
is limited epidemiological data on the frequency of EHI within the high school
setting, which hinders the development and distribution of aggressive
prevention campaigns. Therefore, the purpose of this current study was to
examine epidemiological data of EHI during 2005/2006 – 2010/2011.  Data was collected using the National High
School Sports-Related Injury Surveillance System, High School RIO from 100 high
schools during the 2005/2006 – 2010/2011 seasons.  The high school RIO system included 9 sports
since the 2005/2006 season and 11 additional sports starting in the 2008/2009
season.  A certified athletic trainer entered
injuries and exposure (numbers of athletes participating in athletic practices
or competitions) into the study website on a weekly basis. The authors
extracted data in 2012 and calculated rate ratios and injury proportion ratios
in a variety of categories (e.g., geographic location; see examples below).  The authors identified that most EHI occurred
during August (60.3%), specifically during preseason (90.4%).  Football had the most EHI cases (74.4%)
resulting in an EHI incidence rate of 4.42 cases per 100,000 exposures.  The frequency of EHI in football is almost
2.5 times greater than the second highest EHI incidence rate, which was girl’s
field hockey, which had a rate of 1.88 per 100,000 exposures.  Florida and Alabama were among the states
with the highest EHI rates in football and across all sports.  EHI was more common among varsity athletes
(58.9%) and after 2 hours into practices (32%). Interestingly, when body mass
index was examined among athletes who suffered from EHI the authors found that
individuals classified as obese had the most EHI events (37%), but EHI cases in
normal weight individuals were higher than overweight individuals (33.4 and
27.4%, respectively).

This study provides clinicians with some
insight into the frequency of EHI, which can help us identify high school
athletes that may need more attention (e.g., football players, athletes having
long practices) to better protect against EHI. 
One particularly interesting finding was that EHI was fairly common
regardless of body mass index. This suggests that EHI can occur in any
population, regardless of obesity, and proper prevention strategies are needed
to decrease the frequency of these EHI cases. 
This study did not include any data on athletes who sustained EHI but
did not miss practice/games, meaning the number of true EHI exposures could be higher.  It is also interesting that EHI was common in
a plethora of states and sports, suggesting that proper heat acclimatization
guidelines are a must for all sports and geographic locations.  Recommendations from the NATA and the Korey Stringer Institute are valuable resources for clinicians
in sports medicine interested in implementing these guidelines, as the number
of states who have proper heat acclimatization guidelines in place is minimal.  With proper guideline recommendations easily
available, how can we better educate our coaches on proper acclimation during
preseason and enforces these guidelines? 
Will required courses on EHI management and treatment for coaches
(similar to requirements in concussion and AED management) overwhelm the
coaches or help strengthen the need for athletic trainers at all secondary

Written by: Neal Glaviano
Reviewed by: Jeffrey Driban

Related Posts:
of Rate and Injury Proportion Ratios
(# competition EHI per # competition athlete exposures) divided by (#
practice EHI per # practice athlete exposures)

Injury Proportion
(# EHI in football per # total injuries and adverse events in football)
divided by (# EHI in all other sports per # total injuries and adverse
events in all other sports)

Kerr ZY, Casa DJ, Marshall SW, & Comstock RD (2013). Epidemiology of exertional heat illness among u.s. High school athletes. American Journal of Preventive Medicine, 44 (1), 8-14 PMID: 23253644