The effect of active hypohydration on cognitive function: A systematic review and meta-analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis
PubMed 30876770 · doi:10.1016/j.physbeh.2019.03.008
What was done
The authors conducted a systematic review and meta-analysis to evaluate the effect of active hypohydration on cognitive performance. They assessed overall cognitive function and underlying domains (complex attention, executive function, learning, and memory), specifically examining whether fluid deficits of ≥2% body mass loss impaired performance compared to euhydration.
What was found
Active hypohydration did not significantly impair overall cognitive performance (g = -0.177; 95% CI: -0.532 to 0.179; P = .331). Individual cognitive domains (complex attention, executive function, learning and memory) were also not impaired (all P > .236), regardless of whether body mass loss was less than or greater than 2%. Statistical heterogeneity varied widely across domains (I² ranging from 0% to 93%).
Why it matters
These findings challenge standard recommendations that advise athletes to avoid moderate dehydration (≥2% body mass loss) on the premise that it degrades cognitive performance.
Limits
The abstract does not disclose the number of included studies or the total sample size. Statistical heterogeneity was high for certain outcomes (I² up to 93%), and participant demographics or specific exercise protocols are not specified.
Cited by
- partial Mild dehydration can impair cognitive and physical performance.
- contradicts Even mild dehydration causes measurable reductions in cognitive and physical performance.
- contradicts Even a slight degree of dehydration diminishes cognitive and physical performance.
- contradicts Even a slight degree of dehydration can impair cognitive and physical performance.
- contradicts Even mild dehydration diminishes cognitive and physical performance.
- contradicts Even slight dehydration impairs cognitive and physical performance.