There has been considerable debate as to whether dehydration – even moderately severe dehydration – has any meaningful effect on aspects of cognitive function. Much of the uncertainty has resulted from poorly designed studies where there are either confounding factors as a result of the methods used to induce dehydration or poorly-chosen and insensitive measures of cognitive function. This new study assessed the effects of mild dehydration on cognitive performance and mood of young males. Twenty-six young men 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 warm (28°C) environment.
Measurements included a comprehensive computerised cognitive test battery, the profile of mood states (POMS) questionnaire and a subjective symptom questionnaire (headache, concentration and task difficulty) that were administered during each trial. Paired t tests compared the DD and DN trials that resulted in a mean body mass loss of 1.6% with the volunteer’s EU trial where body mass was maintained. Dehydration resulted in a reduction in specific aspects of cognitive performance: errors increased on the visual vigilance task, and visual working memory response latency slowed. Fatigue and tension/anxiety increased due to dehydration at rest and fatigue during exercise. Plasma osmolality increased due to dehydration, but resting core (gastrointestinal) temperature was not altered. In conclusion, mild dehydration without hyperthermia in men induced adverse changes in vigilance and working memory, and increased tension/anxiety and fatigue. Although the effects on cognitive performance and mood states are generally small, they may well be sufficient to have important functional consequences during periods of stress.
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Abstract [button text=”View at PubMed” url=”http://www.ncbi.nlm.nih.gov/pubmed/21736786″ target=”_blank” color=”blue”][/button]
[blockquote]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 27·7°C 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 (P = 0·048) and visual working memory response latency slowed (P = 0·021). Fatigue and tension/anxiety increased due to dehydration at rest (P = 0·040 and 0·029) and fatigue during exercise (P = 0·026). Plasma osmolality increased due to dehydration (P < 0·001) but resting gastrointestinal temperature was not altered (P = 0·238). In conclusion, mild dehydration without hyperthermia in men induced adverse changes in vigilance and working memory, and increased tension/anxiety and fatigue.[/blockquote]