Mild dehydration impairs cognitive performance and mood of men

Abstract

The present study assessed the effects of mild dehydration on cognitive performance and mood of young males. A total of twenty-six men (age 20·0 (SD 0·3) years) participated in three randomised, single-blind, repeated-measures trials: exercise-induced dehydration plus a diuretic (DD; 40 mg furosemide); exercise-induced dehydration plus placebo containing no diuretic (DN); exercise while maintaining euhydration plus placebo (EU; control condition). Each trial included three 40 min treadmill walks at 5·6 km/h, 5 % grade in a 27·78C environment. A comprehensive computerised six-task cognitive test battery, the profile of mood states questionnaire and the symptom questionnaire (headache, concentration and task difficulty) were administered during each trial. Paired t tests compared the DD and DN trials resulting in .1 % body mass loss (mean 1·59 (SD 0·42) %) with the volunteer's EU trial (0·01 (SD 0·03) %). Dehydration degraded specific aspects of cognitive performance: errors increased on visual vigilance (P¼0·048) and visual working memory response latency slowed (P¼ 0·021). Fatigue and tension/anxiety increased due to dehydration at rest (P¼ 0·040 and 0·029) and fatigue during exercise (P¼0·026). Plasma osmolality increased due to dehydration (P,0·001) but resting gastrointestinal temperature was not altered (P¼0·238). In conclusion, mild dehydration without hyperthermia in men induced adverse changes in vigilance and working memory, and increased tension/anxiety and fatigue.Key words: Vigilance: Reaction time: Reasoning: Memory: FurosemideThe most comprehensive studies that evaluated the effects of dehydration on cognitive performance were conducted more than 20 years ago in laboratories located in a hot climate (1,2) . These studies employed a combination of highheat and aerobic exercise to rapidly produce dehydration. Subsequently, at least six other studies have evaluated the influence of body water loss via exercise in the heat (3 -5) and suggested that mild dehydration adversely affects cognitive function at approximately 2 % or more body mass loss, but not at 1 % body mass loss (1,2,5) . However, because body water loss and hyperthermia (i.e. resulting from exercise in a hot environment) were both present in these studies, the effects of dehydration alone could not be examined. Recently, three studies have examined dehydration without inducing hyperthermia (3,6,7) , via passive water restriction or prolonged exercise in a mild environment. These studies induced a narrow range of moderate dehydration (2·6-2·8 %) and therefore did not determine whether more modest levels of dehydration affect cognitive function.The present investigation was designed to assess the effects of mild dehydration, between 1 and 2 % body water loss, on cognitive performance and mood of healthy young males. Few studies have evaluated the effects of such mild dehydration in either men or women (7,8) . To isolate mild dehydration as the sole independent variable, body water loss was induced by mild exercise in a mild environ...

The use of moderated mediated analysis to study the influence of hypo-hydration on working memory

“…2) and previous findings: using the same paradigm, drinking prevented a decline in episodic memory and focussed attention (13). Yet the present report contrasts with previous reports in that working memory was not disrupted by a loss of 1-2% of body mass (4,(8)(9)(10) and that even a loss of more than 2% has only sometimes (4-8) been found to be disruptive.…”

“…Although there are reports stating that a loss of body mass greater than 2% disrupts working memory (4,5), this finding has not always been replicated (6)(7)(8). Working memory has never been reported to be disrupted by a loss of 1-2% of body mass (4,(8)(9)(10). As such, if the use of moderated mediation can demonstrate that a small difference in hydration can be disruptive under some conditions, the value of this novel statistical approach would be demonstrated.…”

Cognitive and perceptual responses during passive heat stress in younger and older adults

“…Notably, mild dehydration (i.e., Յ2% body weight loss) is usually associated with impairments in various aspects of cognitive function, including aspects of attention (5), memory (7,15,20), and executive function (6,7,20). Although this study was not designed to evaluate hydration status as a modulator of cognitive function, it is notable that body weight decreased on average less than 2% in the younger and older subjects.…”

“…Older adults are at an increased risk of morbidity and mortality during heat waves (15,20). Impaired physiological responses to heat stress likely contribute to this increased risk (23, 29, 33-36, 63, 64).…”

Nutra-ergonomics: influence of nutrition on physical employment standards and the health of workers

“…However, we commonly associate this as only a problem in physically demanding situations and harsh environments. It is well evidenced that there is a difference in physiological stress between euhydrated and dehydrated individuals, with several reviews indicating minimal dehydration (as low as 1%-2% body mass loss) potentially affecting mood, attention, reaction time, vigilance, working memory, and increased tension/anxiety (American Dietetic Association 2009; Ganio et al 2011;Masento et al 2014;Maughan 2003;Maughan et al 2007). Moderate dehydration (ϳ2% body mass loss) has commonly been associated with detrimental physiological effects and reductions in endurance exercise performance, particularly in hot conditions (Burge et al 1993;Ebert et al 2007;Lopez et al 2011;Maughan et al 1996;McConell et al 1997;Sawka et al 2007).…”