title: Two nights of sleep deprivation with or without energy restriction does not impair the thermal response to cold.
abstract: OBJECTIVE
  In persons completing exhaustive daily exercise, sleep and energy restriction have been highlighted as risk factors for hypothermia in cold environments. The present study therefore sought to determine the effect of sleep deprivation (SDEP), with and without energy restriction, on the thermal response to cold.
  
  
  METHODS
  In a random order, ten recreationally active men (mean ± SD: age 25 ± 6 years, body fat 17 ± 5 %) completed three 53 h trials: a control (CON: 436 min/night sleep), SDEP (0 min sleep), and sleep deprivation and energy restriction (SDEP + ER: 0 min sleep and 10% daily energy requirements). Exhaustive exercise was completed after 5 and 29 h. After 53 h participants completed a semi-nude seated cold air test (CAT, 0 °C), for 4 h or until rectal core temperature (T re) reached 36 °C.
  
  
  RESULTS
  Two nights of sleep and energy restriction did not impair the thermal response to cold (T re, CON 36.15 ± 0.20 °C, SDEP 36.30 ± 0.15 °C, SDEP + ER 36.25 ± 0.20 °C, P = 0.25). Rewarming was also similar as indicated by 1 h post-CAT T re (P = 0.78). In contrast, perceived thermal discomfort during the initial hour of the CAT tended to be greater after SDEP and SDEP + ER (P ≤ 0.1).
  
  
  CONCLUSIONS
  Sleep and energy restriction, at least as evaluated within this experiment, should be considered minimal risk factors for hypothermia. The greater perception of cold discomfort at the same body temperature suggests that sleep and energy restriction may actually reduce cold injury risk, as people are likely to engage earlier in normal behavioral cold adaptation.
authors.affiliation: Extremes Research Group, Bangor University, Bangor, LL57 2PZ, UK. s.j.oliver@bangor.ac.uk.
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Oliver
authors.affiliation: Extremes Research Group, Bangor University, Bangor, LL57 2PZ, UK.
authors.forename: Adam D
authors.initials: AD
authors.lastname: Harper Smith
authors.affiliation: Extremes Research Group, Bangor University, Bangor, LL57 2PZ, UK.|Department of Nutrition and Dietetics, Monash University, Melbourne, Australia.
authors.forename: Ricardo J S
authors.initials: RJ
authors.lastname: Costa
authors.affiliation: Institute of Sports Science, Leibniz Universität Hannover, Hannover, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Maassen
authors.affiliation: Department for Health, University of Bath, Bath, UK.
authors.forename: James L J
authors.initials: JL
authors.lastname: Bilzon
authors.affiliation: Extremes Research Group, Bangor University, Bangor, LL57 2PZ, UK.
authors.forename: Neil P
authors.initials: NP
authors.lastname: Walsh
mesh_terms: D000328:Adult; D031204:Caloric Restriction; D003080:Cold Temperature; D004734:Energy Metabolism; D006801:Humans; D008297:Male; D012892:Sleep Deprivation / Q000503:physiopathology*; D022722:Thermogenesis
keywords: Cold injury; Hypothermia; Sleep loss; Thermogenesis; Thermoregulation