Exertional Heat Illness Recovery and Recurrence

Introduction Exertional heat illness (EHI) is a threat to force health and readiness. EHI recovery can entail lengthy periods of lost duty time as providers ensure that patients have completely recovered and that the risk for recurrent EHI is low. Although EHI recurrence is a common concern, there is little research to inform or predict EHI recurrence. Here we describe characteristics associated with EHI duty restrictions and use them to predict EHI recurrence and prognosis. Materials and Methods We studied a retrospective cohort of 1,742 US Army soldiers who received EHI duty restrictions because of a recent EHI diagnosis between July 2014 and April 2017. We used EHI complications, medical history, and demographics to predict EHI recurrence. The study protocol was approved by the Naval Medical Center Portsmouth Institutional Review Board. Results 4.4% of soldiers had recurrent EHI. Among soldiers receiving an EHI profile, a history of another prior EHI was rare (5.6%) but was strongly associated with recurrent EHI (HRadj: 7.37, 95% CI: 4.24-12.81). These associations were consistent across heat exhaustion (HE), heat injury (HI), and heat stroke (HS) cases. Shorter profile durations were associated with reduced risk for recurrence, but this association was mostly attributable to milder EHI events. Based on total duty restriction days, HI represented a greater disease burden than HS or HE. Recurrent EHI was more common among soldiers who had been on an HI (4.6%) or HS (6.1%) profile than an HE profile (3.7%), although these differences were not statistically significant. Clinical complications (e.g., kidney injury, rhabdomyolysis, respiratory/cardiovascular distress, inpatient/ICU admission) were not associated with EHI recurrence. Conclusions Among soldiers on EHI duty restrictions, prior EHI is rare but strongly associated with risk for yet another EHI. The clinical characteristics (e.g., profile duration, complications) of a prior EHI were not associated with risk for recurrent EHI. Further research should characterize the role of EHI severity in return to duty and validate HI as a diagnostic category.