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•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. © 2011 The Authors.