The effect of active hypohydration on cognitive function: A systematic review and meta-analysis

Area of Science:

• Sports Science
• Human Physiology
• Cognitive Neuroscience

Background:

• Hypohydration is commonly believed to impair cognitive function, especially in athletes.
• Athletes are often advised to avoid dehydration (≥2% body mass loss) to maintain cognitive performance.
• Existing research presents conflicting findings on the effects of hydration status on cognition.

Purpose of the Study:

• To systematically evaluate the impact of hypohydration on cognitive function.
• To determine if a critical water deficit (≥2% body mass loss) impairs cognitive performance.
• To investigate the effects of hypohydration on specific cognitive domains.

Main Methods:

• Systematic literature search for relevant studies.
• Meta-analysis of selected studies examining cognitive performance under different hydration states.
• Analysis of cognitive domains including attention, executive function, and memory.

Main Results:

• Overall cognitive performance was not significantly impaired by hypohydration (p=0.331).
• No significant impairment was observed in complex attention, executive function, or learning and memory (all p>0.236).
• These findings held true regardless of the extent of fluid loss (less than or greater than 2% body mass loss).

Conclusions:

• Hypohydration does not appear to compromise overall cognitive function or its subdomains.
• Current recommendations advising athletes to avoid moderate hypohydration for cognitive performance are not supported by this meta-analysis.
• Further research may be needed to understand the nuances of hydration and cognitive performance in diverse athletic populations.