Jesse N.L. Sims1, Hannah R. Koch1, Mitchell E. Zaplatosch1, Travis Anderson2, Laurie Wideman, FACSM1, William M. Adams, FACSM2, Jessica McNeil1. 1University of North Carolina Greensboro, Greensboro, NC. 2United States Olympic and Paralympic Committee, Colorado Springs, CO.

BACKGROUND: Elevated morning concentrations of cortisol and copeptin are associated with poor executive function, but the influence of these hormones on cognitive function (cognitive inhibition domain, i.e., response inhibition and interference control) following sleep in hot environmental conditions is not known. This study examined the influence of sleep environment on cortisol and copeptin and their interaction with cognitive inhibition (CI). METHODS: Ten healthy adults (female, n=1; age, 25±4 y; height, 177.9±7.4 cm; body mass, 75.8±13.8 kg; body fat, 13.5±7.1%) completed two nights of in-laboratory assessments while sleeping in temperate (TTEMP, 25°C, 30% RH) and hot (THOT, 30°C, 30% RH) environmental conditions. Upon awakening, blood was collected to examine serum copeptin, and salivary samples were collected 0, 30, and 45 minutes post-awakening, and the greatest morning cortisol concentration (CPEAK) was determined. CI was assessed via the Stroop Color Word Interference task with inhibitory control (measured by inverse incongruency and inverse congruency) reflecting the participants’ ability to resist distractions and respond faster to stimuli, indicating better cognitive performance. Paired samples t-tests evaluated between-condition differences in hormones and CI between sleep environments. Linear mixed models assessed the effect of hormones and environmental conditions on CI. RESULTS: Hormone concentrations did not differ between conditions (mean±SD, [collapsed across conditions], Copeptin, 8.77±3.13pmol/L; CPEAK, 21.83±5.62 ng/mL (p>0.05). There were no differences in CI across conditions when measured by inverse incongruency (MD [95% CI], -27.73 ms [-107.88, 52.42], p=0.45) or inverse congruency (8.29 ms [-38.18, 54.78], p=0.69). When controlling for environmental conditions, higher CPEAK was associated with lower CI (β = -8.68 [95%CI, -14.71, -2.54], p=0.02) however, there was no significant effect of serum copeptin concentrations on CI (p>0.05). CONCLUSIONS: Higher awakening cortisol levels following a bout of sleep in a hot environment were associated with reduced incongruency, or an ability to display interference control and resist distractions during a computer-based cognitive inhibition task. Changes in environmental sleeping conditions may not affect CI the next morning, however, the effect of morning cortisol concentrations on this response requires further exploration.

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