Fatal Exertional Heat Stroke Trends in Secondary School Sports From 1982 Through 2022

Abstract

Background:

Exertional heat stroke (EHS) is a leading cause of secondary school sport-related death; however, a longitudinal analysis on observed trends is lacking. Our purpose was to describe EHS deaths in United States secondary school athletes since the 1982/1983 academic year.

Hypothesis:

EHS deaths will be primarily represented by football athletes and have a stable or increasing trend across a decade-by-decade analysis.

Study Design:

Descriptive epidemiology study.

Level of Evidence:

Level 4.

Methods:

EHS deaths in secondary school sports from July 1, 1982 through June 30, 2022 captured in the National Center for Catastrophic Sports Injury Research database were included (n = 67). Chi-square test of goodness of fit (alpha = 0.05), incidence rate ratios, and 95% CIs of differences in number of deaths between the 4 decades are reported.

Results:

Of 67 deaths, 66 (98.5%) were male. Ages ranged from 13 to 18 years. Football accounted for 63 (94%) of deaths, with basketball (n = 2), soccer (n = 1), and track and field (n = 1) accounting for the remainder. The southern region had the largest number of deaths, n = 50 (74.6%). Most deaths occurred in August (n = 38), followed by July (n = 15) and September (n = 9). Stratified into 4 separate 10-year periods, the proportion of EHS deaths differed significantly across time (χ²(3, n = 67) = 8.72; P = 0.03). The period 2002-2011 had the highest number of EHS deaths (n = 26), 1982-1991 had 9, while both 1992-2011 and 2012-2021 had 16 deaths.

Conclusion:

The most recent decade shows a 38% reduction from the peak decade (2002-2011, n = 26), but remains similar to 1982-1991.

Clinical Relevance:

Continued efforts are required to prevent catastrophic sport-related death due to EHS. Secondary school EHS deaths are overwhelmingly represented by football, most commonly in August, and in the south. This emphasizes the need for secondary schools to be equipped with basic tools and policies to saves lives.

Exertional heat stroke (EHS) has been a consistent top cause of sudden death in sport since tracking began around the 1980s.^6,22 EHS has largely afflicted football athletes, those participating in warm weather events, and those doing intense exercise.^14,17,19 While EHS can be multifactorial, the lifesaving medical standards and equipment have become clear. EHS is largely survivable without complications when aggressive cold water whole-body immersion is delivered and body temperature is reduced below 40°C within 30 minutes of onset.^4,9,15,16,28 While EHS survival has been documented, unfortunately, deaths have continued to occur.^6,17,19,22 A reason for this may be due to differences in access to both the equipment needed to save an EHS victim and appropriate medical professionals, specifically at the secondary school level. Currently, 34% of United States (US) secondary schools with athletics programs do not have an athletic trainer - the main person responsible for the day-to-day health and wellbeing of secondary school student-athletes. ²⁴ The athletic trainer is also the person primarily responsible for the policies and procedures in the event of a sport-related medical emergency at the school. Access to athletic training services has seemingly remained unchanged since initial evaluations of athletic training service access published in 2015 to 2019 suggested that 30% to 34% of schools had an athletic trainer employed to some degree.^18,24 This deficiency provides a greater opportunity for student-athlete deaths when catastrophic events occur.

Although in recent decades the standards and policies to treat EHS have improved in secondary school settings and the profession of athletic training,^{1,20,21,23,25,26} EHS deaths continue to occur.^6,17,19,22 The trends in these deaths have yet to be elucidated as a corresponding decade-by-decade analysis has never been performed. Available data have either focused on concise periods that are less than a decade, or a specific sport. An analysis looking at EHS football deaths between 1980 and 2014 revealed 61 American football player deaths (across all levels of sport) and was the most expansive analysis of organized sport-related EHS deaths to date. ¹⁷ However, the analysis focused on the environmental conditions surrounding these deaths, and not the incidence of EHS, nor did it include sports outside of football. In another football-centric analysis, 243 secondary school and college fatalities over the course of 20 years revealed a total of 30 secondary school EHS deaths, for an annual mean of 1.5 per year. ⁶ To examine all types of exertional heat illnesses (EHIs) across all secondary school sports, an analysis of a 6-year period from 100 schools in the National High School Sports-Related Injury Surveillance System, High School RIO found that EHI rates were highest in football (4.42 per 100,000 athlete-exposures), followed by girls field hockey (1.88 per 100,000 athlete-exposures) and girls lacrosse (0.82 per 100,000 athlete-exposures). ¹⁹ There was a similar overall EHI rate for boys’ and girls’ sports (0.35 vs 0.37 per 100,000 athlete-exposures, respectively). ¹⁹ However, these data do not provide a separate analysis of any EHS deaths or rate of deaths in secondary school athletes from EHS.

Currently, the number of secondary school athlete deaths due to EHS has never been evaluated across sports or over a period of decades. Whereas it may be above the reach of such analysis to determine the cause or interaction of any factors on the occurrence of these deaths, the directionality and volume of EHS deaths since tracking started in the 1980s remains unknown. Understanding the trends in EHS deaths and how these trends occur across various sports would greatly improve our understanding of the evolving risk of EHS in secondary sport, with the hope that it may help to direct efforts to reduce preventable deaths. The only dataset available to perform such an analysis is the National Center for Catastrophic Sports Injury Research (NCCSIR). Therefore, the purpose of this study was to describe EHS deaths in US secondary school athletes since the 1982/1983 academic year that are available through the NCCSIR database.

Methods

This study was conducted in collaboration with the NCCSIR. The study was approved by the institutional review board at the University of North Carolina.

Case Collection and Inclusion Criteria

Catastrophic sport-related EHS deaths in secondary school sports in the last 40 years (from July 1, 1982 through June 30, 2022) captured in the NCCSIR database were included in this descriptive epidemiological study (n = 67). Any nonsport-related deaths or cases of EHS survival were excluded. Event details were captured through systematic media searches of publicly available news reports and reports submitted directly to the NCCSIR.

Athlete Details

Characteristics of the sex, age, sport, geographic region, month, and event type (competition/game, conditioning, practice, scrimmage, strength/weight session, or other) were collected. Geographic region was classified based on the 4 major regions of the United States as described by the US Census: Northeast, Midwest, South, and West (including Hawaii and Alaska).

Incidence Calculations

Athlete population statistics retrieved from the NFHS participation data is provided per sport. Sports included baseball, football, field hockey, softball, and both boys and girls teams for the following sports: basketball, cheerleading, cross country, equestrian, golf, gymnastics, ice hockey, lacrosse, rowing, skiing, soccer, swimming, tennis, track and field, volleyball, water polo, and wrestling. All incidence rates and 95% CIs are reported per athlete-season (AS) of participation.

Statistical Analysis

Descriptive statistics were performed for athlete characteristics. A 5-year rolling mean was provided over the 40-year period. A chi-square test of goodness of fit examined differences in the number of deaths between each 10-year period (alpha = 0.05). Incidence rate ratio (IRRs) and 95% CIs were used to examine differences between the 10-year periods.

Results

A total of 67 deaths due to EHS in secondary school sports were identified. Of the 67 deaths, 66 (98.5%) were male. Ages ranged from 13 to 18 years, with 16 (n = 20) and 17 (n = 19) years old making up 58.3% of all deaths (Table 1). Football accounted for 63 (94%) of the deaths, while basketball (n = 2), soccer (n = 1), and track and field (n = 1) accounted for the remaining deaths (Table 1). The month of August accounted for the greatest deaths (n = 38), followed by July (n = 15) and September (n = 9) (Figures 1 and 2). Of the 63 football deaths, only 4 occurred between May and June. The southern region had the largest number of deaths, n = 50 (74.6%) (Table 1 and Figure 3). Official school practice represented most deaths, n = 56 (83.6%; Table 1). Of the 4 nonfootball deaths, 3 occurred in the months of July to August (1 from September to October), 3 were in the south (1 in the west), and all occurred during practice or conditioning sessions.

Table 1.

Descriptive data for US secondary school athlete EHS deaths from academic years 1982/1983 to 2021/2022

	Total (n)	Percent
Sport
Football	63	94
Basketball	2	3
Soccer	1	2
Track and field	1	1
Event type
Practice	56	84
Conditioning	4	6
Other	3	4
Competition/game	1	2
Scrimmage	1	1
Not identified	2	3
Geographical region
South	50	75
Midwest	9	13
West	6	9
Northeast	2	3
Sex
Female	1	1.5
Male	66	98.5
Age, y
13	3	4.5
14	8	11.9
15	12	17.9
16	20	29.9
17	19	28.4
18	3	4.5
Unknown	2	3.0

EHS, exertional heat stroke; US, United States.

Figure 1.

US secondary school athlete EHS deaths from academic years 1982/1983 to 2021/2022 by month. Number above each bar represents the total number of deaths for that month. EHS, exertional heat stroke; US, United States.

Figure 2.

US secondary school athlete EHS deaths by 5-year block and month from academic years 1982/1983 to 2021/2022. EHS, exertional heat stroke; US, United States.

Figure 3.

US secondary school athlete EHS deaths from academic years 1982/1983 to 2021/2022 by deidentified state and geographic region (n=67). EHS, exertional heat stroke; US, United States.

When stratified into four 10-year periods, the proportion of EHS deaths was significantly different across time (χ²(3, n = 67) = 8.72; P = 0.03). The period 2002-2011 had the highest number of EHS deaths (n = 26), while both 1992-2011 and 2012-2021 had 16 deaths, and 1982-1991 had 9 deaths (Figure 4). These outcomes were similar when examined as incidence rates. To assess decade-based trends, the first decade was utilized as the reference category for the IRR. This revealed that the incidence rate in the third decade (2002-2011) was 2.09 times higher than the first decade (1982-1991) (Table 2). The overall male football incidence rate revealed 1.57 male football deaths for every 1,000,000 AS. Due to low number of events outside of male athletes or the sport of football, incidence rates per 1,000,000 AS are reported only for these 2 characteristics.

Figure 4.

US secondary school athlete EHS deaths from academic years 1982/1983 to 2021/2022. Gray blocks distinguish separate decades; 5-year rolling mean represents the mean yearly deaths based on previous 5-year numbers. *Chi-square goodness of fit was significant for 2002-2011 block (P = 0.03). EHS, exertional heat stroke; US, United States.

Table 2.

US secondary school athlete EHS death rates by characteristic

	Events, N	AS, N	Rate per 1,000,000 AS (95% CI)	IRR (95% CI)
Overall	67	258,369,358	0.26 (0.2, 0.32)
Athlete sex
Female	1	103,543,589	NR a
Male	66	154,825,769	0.43 (0.32, 0.53)
Unknown	2	-	-
Decade
1982-1991	9	51,460,875	0.17 (0.06, 0.29)	1.00 (reference)
1992-2001	16	60,723,260	0.26 (0.13, 0.39)	1.51 (0.67, 3.41)
2002-2011	26	71,197,295	0.37 (0.22, 0.51)	2.09 (0.98, 4.46)
2012-2021	16	74,987,928	0.21 (0.11, 0.32)	1.22 (0.54, 2.76)
Sport
Female basketball	1	16,911,215	NR
Male basketball	1	21,360,026	NR
Male football	63	40,149,119	1.57 (1.18, 1.96)
Male soccer	1	13,167,786	NR
Male track and field	1	22473848	NR

AS, athlete-season; EHS, exertional heat stroke; IRR, incidence rate ratio; NR, not reliable; US, United States.

^aInjury rates based on cell sizes <5 may not be reliable and therefore are reported here as “NR.”

Finally, states were deidentified and grouped by US region and state to report individual EHS deaths (Figure 3 and Table 1). The overwhelming majority of cases (75%) were in the south, with the northeast representing the smallest number reported (3%).

Discussion

With 40 years of data, this is the largest spanning EHS dataset outside of the military population to date. The main finding from this study is that secondary school EHS deaths have remained steady since the 1980s, with a spike in the number of deaths during the 2002-2011 decade. This spike represented a 100% increase in deaths (2.6 per year) compared with the mean of the previous 2 decades (1.3 per year) (Figure 4). The most recent 10-year decade shows a 38% reduction from the peak decade (2002-2011, n = 26), but is consistent with the years before the 2002-2011 spike. Together, over this 40-year period there was a mean of 1 to 2 deaths per year at the secondary school level from EHS. Other predominant characteristics of these EHS cases included those that were males (98.5%), those between the ages of 16 and 17 years (58.3%), the southern US region (74.6%, Figure 3), and the month of August (52.2%, Figures 1 and 2).

Sex as a factor for EHS deaths should be interpreted with caution. Given that 94% of the cases were in football athletes, this may also explain why the dataset was predominantly male (99%, Table 1). It is likely the inherent sport dynamics, sport timing within the year and safety equipment that may heighten the risk for this population.^3,6,7,11,12 Research in other populations with equal participation in male and female athletes has not resulted in significant differences in EHS risk based on sex. ⁵ Data also suggest that preseason football, when not modified due to increases in wet bulb globe temperature, has similar EHI incidence rates compared with data for men’s and women’s road races (2.10 per 1000 athlete-exposures vs 2.13 per 1000 athlete–exposures, respectively).^13,14 This may suggest that factors aside from sex increase EHS risk, and football may contain many of those risk factors.

EHS risk could be heightened specifically for football due to the protective equipment,^3,29 the hot weather that coincides with the start of the season,^13,17,29 proximity to the beginning of the academic and sports season, and the inherent nature of the training sessions.^6,7,29 Previous publications have also pointed out that strength and conditioning sessions as well as linemen positions are important risk factors.^2,7,8,10,29 Indeed, our data also support that practices or conditioning make up 90% of the activity being done when the EHS occurs and seems to present a greater EHS risk than games. Boden et al ⁷ recently described similar results in their examination of high school and collegiate football deaths (all cause) and found that 87% of deaths occurred during a practice or conditioning session. Deaths were also highest in the month of August (34%), and 97% of all EHS deaths were in linemen. Further data and research are needed to describe and understand the unique risks and prevention strategies for football players given the dominant incidence of EHS cases compared with other sports.

Our state and geographic-based analyses revealed that the southern states represented those with the majority of EHS deaths, which is similar to many previous examinations of secondary school EHS deaths (Figure 3).^6,17,19 Recent data also suggest that it is possible to curb EHS rates with policies directed at heat acclimation and weather-based practice modifications. These findings demonstrate that secondary schools that fall under a state-level requirement (ie, state high school association policy or state law) have greater adoption of heat mitigation and treatment strategies than those that do not. These schools appear to adopt more EHS prevention strategies and be more prepared to manage an EHS if one does occur.^21,26,27 Together, these data suggest that there are opportunities to prevent EHS cases from occurring when state-level requirements exist.

Continued efforts are required to prevent catastrophic sport-related death due to EHS. These data can help provide a foundation to indirectly understand whether EHS fatalities are being impacted by surrounding influences related to EHS risk and treatment. Due to the nature of catastrophic injury reporting, these data should be interpreted as the most conservative estimate, as there are likely deaths that we may not be aware of. Finally, previous data have demonstrated that EHS can have a survival rate as high as 100%.^15,16,28 When proper policies, medical professionals, and lifesaving equipment are implemented, we can save athletes’ lives. Identifying how to provide lifesaving policies and care to all athletes is a necessary gap to close given the low cost and high success of preventing unnecessary EHS deaths.

These data suggest that there are targeted periods, scenarios, conditions, and athletes that make up a large portion of the EHS deaths reported. Secondary school EHS deaths are overwhelmingly represented by football (94%), and are most common in August (52%) and in the southern region (75%). Medical professionals should be highly suspicious of EHS during these common scenarios and conditions for athletes who have been exercising intensely. Knowing how successful aggressive, quick, on-site cooling can be for the survival of EHS patients, it is imperative to ensure that secondary schools are equipped with the basic tools to save a life.

Limitations

The first limitation of our study is that we did not seek to determine any associations or factors related to the trends in these data. We also did not assess access to medical care for these deaths, or any required state level policies that may have impacted survival outcomes. In addition, catastrophic reporting is not mandatory for secondary school athletes or their governing institutions. Therefore, reporting to this database is limited to deaths identified through media searches or by submission from a witness, athlete, or other person connected to the death. We acknowledge that reliance on media reports in retrospective study designs has led to underestimates of the true incidence of catastrophic injuries in athletes due to a lack of case identification. Without a mandatory reporting system and complete athlete database, a precise incidence rate may not be fully realized. Therefore, the incidence rate in this manuscript is a conservative reflection of the true incidence rate.

Conclusion

Secondary school EHS deaths are overwhelmingly represented by football (94%), most common in August (52%; however, 94% of all cases occurred between July and September), and in the southern region (75%). The most recent decade demonstrates a 38% reduction from the previous (peak) decade that had 26 EHS deaths; however, it remains consistent with the rate at which we have seen EHS deaths since the 1980s. When considering our data collectively with recent findings highlighting player position-specific susceptibility in American football, we can hopefully start reshaping coaching education and sport training to address targeted medical issues for specific sports and player positions. Mandated sport-related death reporting for secondary school athletes would improve our understanding and confidence in these trends. It would also allow a clearer understanding of factors associated with those who live and die from EHS. Future research should consider additional factors associated with deaths and survival.