Exertional-related Heat Illness: Effects On Neurocognitive Performance, Mental Health, And Cerebellar Function

There are limited data on the neurocognitive effects of exertional heat illness (EHI). PURPOSE: The purpose of this study was to quantify the effects of exertional heat illnesses (heat exhaustion [HE], heat injury [HI], and exertional heat stroke [EHS]) on neurocognitive performance, cerebellar motor function, and mental health with emphasis on depression symptoms in the acute post-injury period. METHODS: Active-duty servicemembers aged 19-40 who sustained an EHI were enrolled prospectively 1-week after hospital discharge. Subjects were assigned to one of two groups: 1) EHS or 2) HE/HI. The Automated Neuropsychological Assessment Metrics (ANAM) was administered 1-week post-injury and compared to baseline, pre-injury neurocognitive performance scores. The Scale for the Assessment and Rating of Ataxia (SARA) and the Beck’s Depression Inventory II (BDI-II) were also administered at 1-week post injury. RESULTS: Six subjects were enrolled in the EHS group, and 29 subjects were enrolled in the HE/HI group. Mean BDI-II scores for the EHS group (14.33 ± 16.42; range = 1-46) were greater than the HE/HI group (7.86 ± 6.70; range = 0-23) with 1/6 (16.7%) EHS versus 0/29 (0%) HE/HI subjects reporting severe depression symptoms in the 1-week post-injury period. Baseline pre-injury ANAM performance reports were available for comparison in 3/6 EHS subjects and 7/29 HE/HI subjects. There were no clinically meaningful group mean reductions in any ANAM subtests between baseline pre-injury and 1-week post-injury ANAM performance scores within either group according to the reliable change index for EHS (0.11 ± 1.16) and HE/HI (0.06 ± 0.88). Mean SARA scores for the 6 subjects in the EHS group (1.17 ± 1.57; range = 0-4) and 29 subjects in the HE/HI group (0.34 ± 0.64; range = 0-2.5) were within normal limits at 1-week post-injury. CONCLUSION: Regardless of diagnosis, there were no observed negative effects on cerebellar motor function or neurocognitive performance. The mean BDI-II score for the HE/HI group was within the range of 0-13 which is often classified as ‘no depression,’ whereas the EHS group had a mean score within the range of 14-19, classified as ‘mild depression.’ Severe depression symptoms were only present in the EHS group, which warrants additional screening in the clinical setting following EHS.