Original paper
The descriptive epidemiology of sports/leisure-related heat illness hospitalisations in New South Wales, Australia

https://doi.org/10.1016/j.jsams.2007.08.008Get rights and content

Summary

Sport-related heat illness has not been commonly studied from an epidemiological perspective. This study presents the descriptive epidemiology of sports/leisure-related heat illness hospitalisations in New South Wales, Australia. All in-patient separations from all acute hospitals in NSW during 2001–2004, with an International Classification of Diseases external cause of injury code indicating “exposure to excessive natural heat (X30)” or any ICD-10 diagnosis code in the range: “effects of heat and light (T67.0–T67.9)”, were analysed. The sport/leisure relatedness of cases was defined by ICD-10-AM activity codes indicating involvement in sport/leisure activities. Cases of exposure to heat while engaged in sport/leisure were described by gender, year, age, principal diagnosis, type of activity/sport and length of stay. There were 109 hospital separations for exposure to heat while engaging in sport/leisure activity, with the majority occurring during the hottest months. The number of male cases significantly increased over the 4-year period and 45+-year olds had the largest number of cases. Heat exhaustion was the leading cause of hospital separation (40% of cases). Marathon running, cricket and golf were the activities most commonly associated with heat-related hospitalisation. Ongoing development and refinement of expert position statements regarding heat illnesses need to draw on both epidemiological and physiological evidence to ensure their relevance to all levels of risk from the real world sport training and competition contexts.

Introduction

Many studies have described sports-related heat illness and its effects on athletes, including the range of characteristics that require specialist identification.1, 2 Two conditions related to heat stress in sport are of particular clinical significance: exertional heat stroke (with relative thermoregulatory failure) and heat syncope (with circulatory instability resulting in postural hypotension following prolonged high intensity exercise). Distinguishing between heat syncope, post-exercise hypotension, heat exhaustion and heat stroke in the collapsed athlete can be difficult.3

Despite accumulating physiological and clinical observations, there is a paucity of epidemiological data about the risk of sport-related heat illness. This is particularly concerning when position statements issued by various sport-related bodies (for example, 4, 5) assume a well-stated on-going problem. Current evidence is mostly from occasional reports of heat stroke and heat exhaustion during endurance events6 and football.7 Other evidence arises from laboratory studies of exercise thermoregulation and risk factors for sport-related heat illness, such as dehydration. While laboratory studies elucidate thermoregulatory mechanisms and factors impacting on them, they rarely reproduce the exercise intensities and complex thermal environments of real sport and do not consider behavioural moderation of heat stress.8 An objective evidence-base for heat stress policies needs to include epidemiological evidence, particularly when such policies include recommendations for thermal environment limits. This study therefore provides new epidemiological data on sports/leisure heat illness hospitalisations in New South Wales (NSW), Australia over a 4-year period.

Section snippets

Methods

All in-patient separations/discharges from NSW acute hospitals between January 2001 and December 2004, inclusive, were obtained from the In-Patient Statistics Collection (ISC), which covers 100% of all NSW hospitalisations. To minimize double counting of multiple admissions for the same heat incident, admissions to non-acute hospitals were excluded.

All separations of persons from NSW acute hospitals with an International Classification of Diseases (10th revision, Australian Modification)

Results

There were 109 hospital heat exposure separations due to sport/leisure activity in NSW, representing 12% of all 905 hospitalisations for exposure to heat over the 4-year period. Ninety-four cases (86%) had both an external cause and a relevant diagnosis code; 13 (12%) cases were identified by diagnosis codes alone and two cases by an external cause alone.

The annual number of cases was 12 (7Males [M]) in 2001, 26 (15M) in 2002, 32 (26M) in 2003 and 39 (27M) in 2004. This rise was statistically

Discussion

This 4-year population-based study found sport/leisure to account for 12% of all heat-related hospitalisations. As only cases positively identified with an ICD-10-AM sport/leisure activity code were included, our study is likely to be an underestimate of the number of cases. Marathon running, cricket and golf were associated with a relatively high number of hospitalisations, consistent with a 2-year Australia-wide review.10 Unfortunately, appropriate exposure data were not available for NSW to

Acknowledgements

The ISC data was accessed via the Health Outcomes Information Statistical Toolkit (HOIST) created and maintained by the Centre for Epidemiology and Research at the NSW Department of Health. Dr. Brotherhood provided valuable comments on draft versions. CF was supported by a National Health and Medical Research Council Principal Research Fellowship. SB was supported by the NSW Injury Risk Management Research Centre.

References (10)

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