Nonfatal Sports and Recreation Heat Illness Treated in Hospital Emergency Departments --- United States, 2001--2009

Although heat illness is recognized as a leading cause of death and disability during participation in U.S. high school and collegiate athletics (1), the incidence of heat illness among younger children and adults participating in sports and recreational activities is unknown. To examine the incidence and characteristics of nonfatal sports and recreation heat illness among persons of all ages, CDC analyzed 2001--2009 data from the National Electronic Injury Surveillance System -- All Injury Program. This report describes the results of that analysis, which found that an estimated 5,946 persons were treated in U.S. emergency departments (EDs) each year for a heat illness sustained while participating in a sport or recreational activity, for an estimated annual rate of 2.0 ED visits per 100,000 population. Incidence was highest among males (72.5%) and among those aged 15--19 years (35.6%), and 7.1% of patients were hospitalized. These findings highlight the need for effective heat illness prevention messages to target all persons who are physically active, including those who participate in unstructured sports and recreational activities. Specific emphasis should be placed on targeting appropriate prevention messages toward those aged 15--19 years, who are at greatest risk, and their coaches and parents.

The National Electronic Injury Surveillance System (NEISS) is an ongoing surveillance system that monitors consumer product--related injuries treated in U.S. hospital EDs (2). The system is maintained and operated by the U.S. Consumer Product Safety Commission (CPSC). NEISS currently includes 100 hospital EDs, which represent a stratified probability sample of all U.S. and U.S. territory hospitals that have at least six beds and provide 24-hour emergency services. The National Electronic Injury Surveillance System -- All Injury Program (NEISS-AIP) is a subsample of 66 NEISS hospitals. NEISS-AIP tracks all injuries seen in EDs, whether or not they are associated with consumer products, and as such, is a nationally representative dataset on injuries. For each entry, data include up to two consumer product codes and a brief narrative describing the circumstances of the injury.

For this report, NEISS-AIP data were analyzed for a 9-year period from 2001 through 2009. Sports and recreation injuries were first identified and classified into one of 39 mutually exclusive sports and recreation groups by applying an algorithm that considered the consumer products involved (e.g., basketball activity, apparel, or equipment; or football activity, apparel, or equipment) and the narrative description of the incident. Cases were excluded if the incident did not meet the unintentional sports injury definition (e.g., argument or physical assault). After identifying unintentional sports injuries, the subset of cases that were classified within NEISS-AIP having a precipitating or immediate cause of "natural/environmental" or "other specified" were identified. Finally, ED visits for nonfatal heat illness were identified by electronically searching for indicators of heat illness (e.g., "heat exhaustion," "dehydration," or "overheated") in the narrative description. Heat illnesses that were work-related, including military training, were excluded.

Each case was assigned a sample weight based on the inverse probability of selection; these weights were summed to provide national estimates of nonfatal ED visits for heat illness. Rates per 100,000 population were calculated using U.S. Census Bureau population estimates (3). Subgroups with fewer than 20 visits or with a coefficient of variation >30% were considered unstable and were not reported.

During 2001--2009, a total of 983 ED visits for sports and recreation heat illnesses were reported by the 66 participating NEISS-AIP hospitals. These data correspond to an estimated average annual number of 5,946 (95% confidence interval [CI] = 4,194--7,698) ED visits for sports and recreation heat illnesses nationwide during this period, and an estimated annual rate of 2.0 heat illnesses per 100,000 population (CI = 1.4--2.6) (Table 1). Sports and recreation heat illnesses were more common among males (72.5%) and among those aged 10--14 years (18.2%) and 15--19 years (35.6%). They occurred most frequently during July--September (66.4%) (specifically, July [19.8%], August [33.2%], and September [13.5%], with a substantial number of visits also occurring in June [12.9%]). Although the majority (91.9%) of ED visits resulted in the patient being treated and released, 7.1% of patients were hospitalized or transferred to another facility for a higher level of care. Hospitalization was more common among males (8.9%) compared with females (2.4%) and among persons aged ≥55 years (18.8%) compared with persons aged <55 years (4.6%).

Sex-specific and age-specific rates of ED visits for sports and recreation heat illnesses remained consistent during the 9 study years. On the basis of unweighted NEISS-AIP data (national estimates for sex and age groups were unstable by activity), the most common activities leading to ED visits for heat illness for all ages were football (24.7%) and exercise (e.g., walking, jogging, and calisthenics) (20.4%); however, this varied by age group and sex. For males, the most common activity leading to heat illness was football for those aged ≤19 years, exercise for those aged 20--44 years, and golf for those aged ≥45 years (Table 2). Other common activities among males were baseball/softball for those aged ≤14 years and exercise for those aged ≥45 years. For females, the most common activity leading to heat illness was baseball/softball for those aged ≤14 years, track and field for those aged 15--19 years, and exercise for those aged ≥20 years.

Reported by

Julie Gilchrist, MD, Tadesse Haileyesus, MS, National Center for Injury Prevention and Control, Matthew W. Murphy, PhD, National Center for Environmental Health, Office of Noncommunicable Diseases, Injury, and Environmental Health; Ellen E. Yard, PhD, EIS Officer, CDC. Corresponding contributor: Ellen E. Yard, [email protected], 770-488-3406.

Editorial Note

Approximately 250 million U.S. residents report occasional participation in sports or recreational activities (4). This report, the first to provide national estimates of heat illness among all sports and recreation participants, found that an estimated 5,946 ED visits are made annually for heat illness that occurs during sports and recreational activities. A 5-year age group, consisting of those aged 15--19 years, represents 35.6% of these ED visits. Heat illness was most frequent during the summer months, a finding consistent with previous reports (5,6).

In the absence of prompt intervention, heat illness can result in permanent morbidity (e.g., organ failure and brain damage) and mortality. Thus, increased emphasis on appropriate primary and secondary prevention strategies is critical.

All heat illnesses are preventable. Everyone engaging in sports or recreational activities is at risk for heat illness and thus can benefit from following established recommendations, the most important of which is primary prevention. Coaches of organized sports teams should schedule frequent rest breaks and encourage fluid consumption (7), particularly on days that are very hot or humid. Practices that begin during summer months should increase frequency, duration, and intensity gradually to allow athletes to acclimate to the heat (8). Participants in recreational activities should be aware of the risk for heat illness and potential prevention strategies. In addition to recommendations for sports teams, recommendations for individual participants include wearing lightweight, light-colored, and loose-fitting clothing; exercising early or late in the day when it is cooler; and having an exercise partner (9).

The findings in this report are subject to at least four limitations. First, only nonfatal heat illnesses treated in EDs were included; thus, this report is an underestimate of all heat illnesses. Second, because no comprehensive data source on national participation in sports and recreational activities exists, rates were based on population estimates and therefore are not as representative as participation-based rates. Third, limited data are available on the circumstances of the event, such as temperature and relative humidity. Finally, although the spatial distribution of heat illness might differ across the United States, NEISS-AIP is designed to provide national estimates only and does not provide state or local estimates.

Untreated heat illness can progress quickly to serious, potentially fatal illness. Thus, everyone should recognize symptoms of heat illness, which include dehydration, nausea, vomiting, headache, dizziness, or a change in mental status (10). When symptoms of heat illness do occur, medical attention should be sought immediately. Information on preventing and responding to heat illness is available at http://emergency.cdc.gov/disasters/extremeheat/heat_guide.asp. In addition, information on preventing heat illness in organized sports is available at http://www.nata.org/health-issues/heat-illness.

Acknowledgments

Thomas J. Schroeder, MS, Arthur K. McDonald, MA, and other staff members of the Div of Hazard and Injury Data Systems, US Consumer Product Safety Commission. Joseph L. Annest, PhD, National Center for Injury Prevention and Control, Office of Noncommunicable Diseases, Injury, and Environmental Health, CDC.

References

1. Mueller FO. Catastrophic sports injury research: twenty-sixth annual report. Chapel Hill, NC: National Center for Catastrophic Sport Injury Research; 2008. Available at http://www.unc.edu/depts/nccsi/AllSport.pdf. Accessed July 19, 2011.
2. US Consumer Product Safety Commission. NEISS All Injury Program: sample design and implementation. Washington, DC: US Consumer Product Safety Commission; 2001.
3. US Census Bureau. Population estimates. Washington, DC: US Census Bureau; 2009. Available at http://www.census.gov/popest/national/asrh/NC-EST2009-sa.html. Accessed July 19, 2011.
4. US Census Bureau. Participation in selected sports activities: 2008. Washington, DC: US Census Bureau; 2011. Available at http://www.census.gov/compendia/statab/2011/tables/11s1248.pdf. Accessed July 19, 2011.
5. Sanchez CA, Thomas KE, Malilay J, Annest JL. Nonfatal natural and environmental injuries treated in emergency departments, United States, 2001--2004. Fam Community Health 2010;33:3--10.
6. CDC. Heat illness among high school athletes---United States, 2005--2009. MMWR 2010;59:1009--13.
7. Von Duvillard SP, Braun WA, Markofski M, Beneke R, Leithäuser R. Fluids and hydration in prolonged endurance performance. Nutrition 2004;20:651--6.
8. Casa DJ, Csillan D. Preseason heat-acclimatization guidelines for secondary school athletics. J Athl Train 2009;44:332--3.
9. CDC. Extreme heat: a prevention guide to promote your personal health and safety. Atlanta, GA: US Department of Health and Human Services, CDC; 2011. Available at http://www.bt.cdc.gov/disasters/extremeheat/heat_guide.asp. Accessed July 19, 2011.
10. Howe AS, Boden BP. Heat-related illness in athletes. Am J Sports Med 2007;35:1384--95.