Core Temperature Lability during Heat Exposure Predicts Cognitive Performance in Persons with Spinal Cord Injury
1Kumar N, 2Graham M, 2Leung P, 1Tittley T, 1Tascione O, 3Bang C, 1Bauman W, 1Handrakis J
1VA RR&D National Center for the Medical Consequences of Spinal Cord Injury, James J. Peters VAMC, Bronx, NY, USA; 2New York Institute of Technology, Department of Physical Therapy, School of Health Professions, Old Westbury, NY, USA; 3Medical Service, James J. Peters VAMC, Bronx, NY, USA
Objective: Previous work from our lab has demonstrated that persons with tetraplegia generally present with lower core body temperature (Tcore). Of note, a limited exposure to cool temperature led to a decline in Tcore and cognitive performance, but a similar cool exposure in able-bodied (AB) individuals did not alter Tcore or cognitive performance. Because of the prior observed effects of cool exposure in those with tetraplegia, the effect of heat exposure on Tcore and cognitive performance in persons with high-level spinal cord injuries (≥T4; Hi-SCI) was determined.
Design/Methods: Eighteen persons with Hi-SCI (C5-T3, AIS A-B) and 17 age and body mass index-matched AB controls, were acclimated to 27°C at baseline (BL) before being exposed to 35°C for up to 120 minutes (Heat Challenge). Tcore (rectal temperature) was continuously measured. Cognitive performance was assessed at BL and at the end of the Heat Challenge using Stroop Color and Word (attention and visual processing speed) and Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) Digit Span tests (working memory). Persons with Hi-SCI were divided into two groups based on the magnitude of change in Tcore to Heat Challenge, High Responder (HR: ≥0.5°C) and Low Responder (LR: <0.5°C).
Results: At BL, average Tcore was 36.60±0.45°C in HR (n=11, C4-T2), 37.11±0.32°C in LR (n=7, C4-T4), and 37.30±0.35°C in AB controls (n=17). At BL, Tcore was different between the HR and AB groups (p<0.001) and between the HR and LR groups (p<0.05). After Heat Challenge, Tcore was not significantly different among the three groups, with Tcore increasing 0.77±0.28°C in HR, 0.28±0.19°C in LR, and -0.06±0.24°C in AB groups. The changes in Tcore post-challenge were significant only in the HR (p<0.0001) and LR (p<0.01) groups. On measures of cognitive performance, the HR group had a significantly greater change in WAIS-IV Sequence scaled-scores compared to the AB group (2.00±1.90 vs. -0.12±1.83; p<0.05, respectively). The changes of the HR compared to AB group in Stroop Word T-scores (7.64±4.63 vs. 2.24±5.66; p=0.057, respectively), and WAIS Forward scaled-scores (1.36±1.21 vs. -0.24±1.82; p=0.067, respectively) approached significance. No differences in change in cognitive performance were found within or between the LR and AB groups. Only the HR group demonstrated significant increases in cognitive performance.
Conclusion: Persons with Hi-SCI who displayed a greater rise in Tcore after heat exposure demonstrated improved cognitive performance vs. AB controls. HR persons generally had a lower Tcore at BL, demonstrating thermodysregulation by (1) an inability to maintain Tcore within the expected range of normothermia at BL and (2) a significant upward drift in Tcore upon heat exposure. Thus, Tcore in the HR group under “normal” ambient conditions impaired cognitive performance. As such, to optimize cognitive performance and quality of life, patient education and interventions that are designed to enhance Tcore should be considered in individuals with Hi-SCI who are identified as HR.
Support: VA Rehabilitation Research and Development Service, Small Projects in Rehabilitation Research (SPiRE): Federal Award Identification Number: I21RX001734 and C2020C)
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