Influence of Variations in Body Hydration on Cognitive Function

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Abstract
Eight healthy men, unacclimated to heat, were submitted to variations in body hydration. The subjects were kept euhydrated, dehydrated by controlled passive hyperthermia or exercise on a treadmill up to a weight loss of 2.8%, or hyperhydrated using a solution containing glycerol, with a total ingested volume equal to 21.4 ml/kg of body weight. On completion of a 90-min recovery period, the subjects were assigned a pedaling exercise on an arm-crank ergometer. Psychological tests were administered 30 min after the phase of hydration variation and 15 min after the arm crank exercise. Both dehydration conditions impaired cognitive abilities (i.e., perceptive discrimination, psycho-motor skills, and short-term memory) as well as subjective estimates of fatigue, without any relevant differences between them. Short-term memory was significantly greater following hyperhydration when compared to euhydration (P < .05). Following arm crank exercise, further effects of dehydration were found for tracking performance only (P < .05). Moreover, long-term memory was impaired in both control and dehydration situations, whereas there was no decrement in performance in the hyperhydration condition.