Effects of hypohydration and fluid balance in athletes' cognitive performance: a systematic review.
Level 1 - systematic review of randomized trials
Systematic review of 24 trials evaluating hydration interventions during exercise
PubMed 36032481 · doi:10.4314/ahs.v22i1.45
What was done
Systematic review searching PubMed, SPORTDiscus, and EBSCO databases for studies evaluating the effects of hypohydration, fluid balance, and heat on cognitive performance in sport (including vigilance, decision-making, mood, and perceived exertion). Eligible studies included trials where exercising participants either received fluid or were restricted from fluid intake.
What was found
Twenty-four trials from 24 publications were included, totaling 493 participants. Significant hypohydration (>2% body mass loss) was reported in 16 publications. Five articles demonstrated that hypohydration of 3% to 5% body mass loss combined with heat stress and limited fluid intake impaired cognitive performance. Cognitive deficits were consistently accompanied by mood disturbance, fatigue, and elevated ratings of perceived exertion.
Why it matters
This review clarifies that cognitive degradation in athletes primarily emerges at higher levels of fluid deficit (3–5% body mass loss) under heat stress rather than mild dehydration.
Limits
No quantitative meta-analysis was conducted. Average trial size was small (~20 participants per study). The abstract does not specify participant demographics, sex distribution, or risk of bias, and notes that sport-specific cognitive testing protocols across studies remain equivocal.
Cited by
- supports Mild dehydration can impair cognitive and physical performance.