Exertional heat illness complications and prognosis among service members

To examine exertional heat illness (EHI) complications and their associations with post-EHI outcomes. In retrospective cohort of 24,121 service-members (SM) with first-time EHI in 2012-2022, we analyzed six EHI complications: rhabdomyolysis, acute kidney injury (AKI), neurological symptoms, acidosis, respiratory/cardiovascular distress, other organ damage. Post-EHI outcomes included medical military separation and chronic diseases. Using clustering, SM were placed into six clusters based on patterns of complications: mild (81%; no complications), AKI/no rhabdomyolysis (5%), rhabdomyolysis/no AKI (6%), rhabdomyolysis/AKI (5%) and neurological symptoms (2%). AKI and/or rhabdomyolysis clusters were associated with being male, obese, no chronic conditions, reduced medical separation risk, and increased AKI risk; the smaller neurological cluster had more females, chronic conditions, and separation risk. EHI clusters have differential associations with both pre-EHI demographics/history and post-EHI outcomes.