Mild Dehydration Affects Mood in Healthy Young Women,

Abstract

Limited information is available regarding the effects of mild dehydration on cognitive function. Therefore, mild dehydration was produced by intermittent moderate exercise without hyperthermia and its effects on cognitive function of women were investigated. Twenty-five females (age 23.0 ± 0.6 y) participated in three 8-h, placebo-controlled experiments involving a different hydration state each day: exercise-induced dehydration with no diuretic (DN), exercise-induced dehydration plus diuretic (DD; furosemide, 40 mg), and euhydration (EU). Cognitive performance, mood, and symptoms of dehydration were assessed during each experiment, 3 times at rest and during each of 3 exercise sessions. The DN and DD trials in which a volunteer attained a ≥1% level of dehydration were pooled and compared to that volunteer's equivalent EU trials. Mean dehydration achieved during these DN and DD trials was -1.36 ± 0.16% of body mass. Significant adverse effects of dehydration were present at rest and during exercise for vigor-activity, fatigue-inertia, and total mood disturbance scores of the Profile of Mood States and for task difficulty, concentration, and headache as assessed by questionnaire. Most aspects of cognitive performance were not affected by dehydration. Serum osmolality, a marker of hydration, was greater in the mean of the dehydrated trials in which a ≥1% level of dehydration was achieved (P = 0.006) compared to EU. In conclusion, degraded mood, increased perception of task difficulty, lower concentration, and headache symptoms resulted from 1.36% dehydration in females. Increased emphasis on optimal hydration is warranted, especially during and after moderate exercise.

The use of moderated mediated analysis to study the influence of hypo-hydration on working memory

“…2) and previous findings: using the same paradigm, drinking prevented a decline in episodic memory and focussed attention (13). Yet the present report contrasts with previous reports in that working memory was not disrupted by a loss of 1-2% of body mass (4,(8)(9)(10) and that even a loss of more than 2% has only sometimes (4-8) been found to be disruptive.…”

“…Although there are reports stating that a loss of body mass greater than 2% disrupts working memory (4,5), this finding has not always been replicated (6)(7)(8). Working memory has never been reported to be disrupted by a loss of 1-2% of body mass (4,(8)(9)(10). As such, if the use of moderated mediation can demonstrate that a small difference in hydration can be disruptive under some conditions, the value of this novel statistical approach would be demonstrated.…”

Water consumption, not expectancies about water consumption, affects cognitive performance in adults

“…In adults, dehydration to a loss of more than 2% body weight, induced by heat exposure or exercise, results in poor performance on tasks assessing memory and psychomotor performance (Gopinathan, Pichan, & Sharma, 1988;Sharma, Sridharan, Pichan, & Panwar, 1986); although see Secher and Ritz (2012) for a discussion of methodological limitations. Subjective feelings of concentration and alertness are also negatively affected (Armstrong et al, 2012;Shirrefs, Merson, Fraser, & Archer, 2004;Szinnai, Schachinger, Arnaud, Linder, & Keller, 2005). Similarly, in children, dehydration negatively affects performance on memory tasks (Bar-David, Urkin, & Kozminsky, 2005;Fadda et al, 2012;Fadda et al, 2008).…”

The Effect of Mild Dehydration Induced by Heat and Exercise on Cognitive Function

“…[2][3][4] Regarding cognitive function, many researchers contend that dehydration leads to reduced cognitive function, [5][6][7][8][9][10] though the evidence is equivocal. [11][12][13][14] One possible reason for the mixed results in the literature is that the methods for testing cognitive function are inconsistent among studies. Because there are many cognitive domains that contribute to cognitive function, some studies focused on specific domains.…”

“…Common interventions include: Water deprivation, 10,19 passive heat stress, 7,11,16 exercise, 11,14,20 combined exercise and heat, 5,6,12 and comparison of dehydration methods. 7,8 Since dehydration can result from various and multiple insults, various dehydration methods must be tested and should reflect the population being studied.…”