Individual risk factors associated with exertional heat illness: A systematic review

Abstract

Despite the widespread knowledge of exertional heat illness (EHI) and clear guidance for its prevention, the incidence of EHI remains high. We carried out a systematic review of available literature evaluating the scientific evidence underpinning the risk factors associated with EHI. Medline, PsycINFO, SportDiscus and Embase were searched from inception to January 2019 with no date limitation, with supplementary searches also being performed. Search terms included permutations of risk and heat illness, with only studies in English included. Study selection, data extraction and quality assessment, using the QUALSYST tool, were performed by two independent reviewers. Of 8898 articles identified by the searches, 42 were included in the systematic review as primary evidence demonstrating a link between a risk factor and EHI. The quality scores ranged from 57.50 to 100%, and studies were generally considered to be of strong quality. The majority of risks attributable to EHI were categorized as those associated with lifestyle factors. The findings from the systematic review suggest complex manifestation of EHI through multiple risk factors rather than any one factor in isolation. Further research is needed to explore the accumulation of risk factors to help in development of effective preventative measures.

Epidemiology of Exertional Heat Illness in the Military: A Systematic Review of Observational Studies

“…Although the evidence was either limited or conflicting, other intrinsic risk factors that were found to have some form of association with EHI were age, marital status, acclimatisation, pre-existing illness, race and genetics. These intrinsic factors are in consonance with a recently published review that identified a variety of intrinsic/individual factors associated with EHI in the general population [ 65 ].…”

“…However, in this review, heat acclimatisation was not significantly associated with EHI. It is important to apply caution when interpreting the association between physical fitness and EHI among military personnel, given that these findings were as a result of failing occupational fitness tests among recruits or new enlistees [ 65 ]. Furthermore, the choice of tests used to assess fitness may not provide true reflections of the aerobic fitness levels of the military personnel.…”

“…Interestingly, pre-existing and concurrent illnesses such as common cold, gastrointestinal and febrile illness which have been documented in the literature to be associated with EHI were found to be a non-significant risk factor in this review [ 65 ]. However, this evidence is limited given that the predictive relationship was investigated by one study [ 57 ].…”

In pursuit of the unicorn

“…Although the pathology of some of the conditions that constitute HI are better understood than NFCI, they can still vary in terms of the organs affected in different individuals and the sensitivity of different individuals to the same conditions and responses. As with NFCI, lists of factors that predispose to HI have been produced (Westwood et al., 2020), but none of these applies in all conditions.…”

Experimental Physiology special issue: Extreme environmental physiology

“…From the pathophysiological/clinical perspective, Trotter and colleagues report that high‐intensity interval exercise reduces tolerance to a simulated haemorrhagic challenge in heat‐stressed individuals (Trotter et al., 2021). There is a systematic review of individual risk factors associated with exertional heat illness (Westwood et al., 2021). Two papers examine the medical emergency of heat stroke: one describes the acute phase response to exertional heat stroke (Iwaniec et al., 2021), the other the impact of prior viral illness on heat stroke severity (Dineen, Ward, & Leon, 2021).…”