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European Journal of Applied Physiology

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01-05-2017 | Original Article

The independent influences of heat strain and dehydration upon cognition

Authors: Anne M. J. van den Heuvel, Benjamin J. Haberley, David J. R. Hoyle, Nigel A. S. Taylor, Rodney J. Croft

Published in: European Journal of Applied Physiology | Issue 5/2017

Abstract

Purpose

Many researchers have addressed the potential effects of hyperthermia and dehydration on cognition, often revealing contradictory outcomes. A possible reason for this inconsistency is that experiments may have been inadequately designed for such effects. In this study, the impact of hyperthermia, dehydration and their combination on cognition were evaluated in eight young males, after accounting for a range of experimental limitations.

Methods

Passive heating and thermal clamping at two mean body temperatures (36.5, 38.5 °C) were performed under three hydration states (euhydrated, 3 and 5% dehydrated) to assess their effects on difficulty-matched working memory and visual perception tasks, and on a difficulty manipulated perceptual task. Data were analysed according to signal detection theory to isolate changes in response sensitivity, bias and speed.

Results

Neither moderate hyperthermia (P = 0.141) nor dehydration (P > 0.604) modified response sensitivity, nor did they significantly interact (P > 0.698). Therefore, the ability to distinguish correct from incorrect responses was unaffected. Nevertheless, hyperthermia, but not dehydration (P = 0.301), reduced the response bias (−0.08 versus 2.2 [normothermia]; P = 0.010) and reaction time (mean reduction 49 ms; P < 0.001), eliciting more liberal and faster responses (P = 0.010). Response bias was reduced for the memory relative to the perceptual task (P = 0.037), and this effect was enhanced during hyperthermia (P = 0.031).

Conclusions

These observations imply that, once potentially confounding influences were controlled, moderate hyperthermia, significant dehydration and their combined effects had insufficient impact to impair cognition within the memory and perceptual domains tested. Nonetheless, moderate hyperthermia elicited more liberal and rapid responses.

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Title: The independent influences of heat strain and dehydration upon cognition
Authors: Anne M. J. van den Heuvel
Benjamin J. Haberley
David J. R. Hoyle
Nigel A. S. Taylor
Rodney J. Croft
Publication date: 01-05-2017
Publisher: Springer Berlin Heidelberg
Published in: European Journal of Applied Physiology / Issue 5/2017
Print ISSN: 1439-6319
Electronic ISSN: 1439-6327
DOI: https://doi.org/10.1007/s00421-017-3592-2

At a glance: The ONWARDS insulin icodec trials

Springer Medicine

The independent influences of heat strain and dehydration upon cognition

Abstract

Purpose

Methods

Results

Conclusions

At a glance: The ONWARDS insulin icodec trials

Springer Medicine

Abstract

Purpose

Methods

Results

Conclusions

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