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; 40mg furosemide); exercise-induced dehydration plus placebo containing no diuretic (DN); exercise while maintaining euhydration plus placebo (EU; control condition). Each trial included three 40min treadmill walks at 5·6km/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.