Water Consumption during a School Day and Children’s Short-Term Cognitive Performance: The CogniDROP Randomized Intervention Trial

Abstract

There is still little research examining the relationship between water consumption in school and specific cognitive performance. The aim of this cluster-randomized intervention CogniDROP trial was to investigate the short-term effects of drinking water during the morning on executive functions. The participants were from the 5th and 6th grade of a comprehensive school in Germany (14 classes, n = 250, 61.6% boys). The classes were randomly divided into an intervention group (an education on healthy drinking behavior and a promotion of water consumption) and a control group. A battery of computerized tasks (Switch Task, 2-Back Task, Corsi Block-Tapping Task and Flanker Task) was used to test executive functions. Urine color and thirst were evaluated to check the hydration level. Physical activity over the past 24 h was measured using GT3X ActiGraph. A non-linear relationship was observed between the amount of drinking water and executive performance. Consuming water up to 1000 mL (or up to 50% of Total Water Intake) had benefits during memory tasks. Urine color and number of steps on the study day correlated with water consumed. The results suggest that a water-friendly environment supports school-aged children in adequate water intake resulting in better cognitive performance, especially short-term memory.

Body Composition and a School Day Hydration State among Polish Children—A Cross-Sectional Study

“…Based on urine osmolality measurement, 84% of children were dehydrated (morning Uosm >800 mOsm/kgH 2 O) at the start of a school day. Drinking water had beneficial effects on memory, verbal reasoning, and vigor [ 37 ].The results of new study of Drozdowska et al suggest that a water friendly environment supports school-aged children in adequate water intake resulting in better cognitive performance, especially short-term memory [ 6 ]. In our study, 53% of all children featured an inadequate level of hydration during their stay at school, which turned out to be a risk factor of difficulties with concentration declared by students and could affect both current and long term learning outcomes.…”

Is there a functional relationship between hydration and memory in children and adolescents? A meta-analysis.

“…The search identified 816 articles using the reference terms proposed, of which only 10 were selected to perform a qualitative synthesis of their content (5 randomized and 5 crossover studies). From the studies evaluated using the RoB 2 (Figures 2) 6,7,10,28,29 , 4 presented some concerns on the overall critical analysis of bias 6,7,10,28 , and one had a high risk of bias 29 . Regarding the crossover studies (Figure 3), all studies showed some concerns on the risk of bias through ROBINS-I 9,24-27 .…”

“…Regarding the participants' characteristics in the selected studies, the sample was composed only of children and adolescents whose ages varied between 4 and 17. Most of the selected studies conducted their interventions within the school where they selected students at random, allocating them into two or three groups, with one being the control and the others for interventions 6,7,10,28,29 . Five studies made a single group and performed the intervention with all participants, evaluating them before and after the intervention 9,[24][25][26][27] .…”

“…One of the studies did not define the amount of water that the participants should drink; however, the individuals participated in a training session on the importance of water intake before the intervention day, and then on the intervention day, they were reminded to drink water during the day. Thus, the children drank water ad libitum, and the total amount of intake was recorded at the end of the school day 28 (Table 2). From the studies included in this research, only the amount of water ingested was measured, while the participant's hydration level was not assessed.…”

“…Concerning the water intake period, half of the studies included in this review ingested it between 30 min to 2 h 7,9,24,27 , while others throughout the school day 6,25,28 . Khan et al (2019) 26 performed two interventions of 4 days each, while low water intake (0.5 L/day) was performed in one group, and there was a high water intake (2.5 L) in the other group.…”