Dehydration (DEH) is believed to impair cognitive performance but which domains are affected and at what magnitude of body mass loss (BML) remains unclear.
To conduct systematic literature review and meta-analysis to determine the effect size (ES) of DEH on cognitive performance and influence of experimental design factors (e.g., DEH > 2% BML).
Thirty-three studies were identified, providing 280 ES estimates from 413 subjects with DEH ranging from 1-6% BML. Outcome variables (accuracy, reaction time), cognitive domains, and methods to induce DEH varied. ES were calculated using standardized mean differences and multivariate meta-analysis.
Impairment of cognitive performance (all domains/outcomes) with DEH was small but significant (ES = −0.21; 95% CI: [−0.31, −0.11], p < 0.0001) with significant heterogeneity (Q(279) = 696.0, p < 0.0001; I2 = 37.6%). Tasks of executive function (ES = −0.24; [−0.37, −0.12]), attention (ES = −0.52; 95% CI: [−0.66, −0.37]), and motor coordination (ES = −0.40; [−0.63, −0.17]) were significantly impaired (p ≤ 0.01) following DEH; and, attention/motor coordination was different (p < 0.001) from reaction time specific tasks (ES = −0.10; [−0.23, 0.02]). BML was associated with the ES for cognitive impairment (p = 0.04); consequently, impairment was greater (p = 0.04) for studies reporting >2% BML (ES = −0.28, 95% CI: [−0.41, −0.16] compared to ≤ 2% (ES = −0.14, 95% CI: [−0.27, −0.00]).
Despite variability among studies, DEH impairs cognitive performance, particularly for tasks involving attention, executive function, and motor coordination when water deficits exceed 2% body mass loss.
Exercise Physiology Laboratory, School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA
Corresponding Author: Mindy Millard-Stafford, firstname.lastname@example.org, 555 14th St NW, School of Biological Sciences, Georgia Tech, Atlanta, GA, 30332, Telephone: (404) 894-6274, Fax: 404 894-9982
All authors had no conflict of interest, including relevant financial interests, activities, relationships, and affiliations to declare relating to this manuscript. The results of the study are presented clearly, honestly, without fabrication, falsification, or inappropriate data manipulation. The results of the present study do not constitute endorsement by the American College of Sports Medicine.
Accepted for Publication: 24 May 2018