Influence of Drinking Water on Cognitive Performance of Schoolchildren - CogniDROP

Question: Water is one of the most important nutrients for physical and mental health. Especially among children, an adequate fluid supply is often insufficient. Preliminary studies indicate that about 17% of 10 to 12 year old children refrain from drinking anything before school starts. This may negatively affect their ability to concentrate. The aim of this interventional study was to investigate short-term effects of an increased water supply affecting the cognitive performance of schoolchildren in everyday conditions.

Methods: 249 5th and 6th graders (aged 11.4 ± 0.7 years) of an comprehensive school in Gelsenkirchen, Germany were included. Children were motivated to drink water before classes (8:00 am) as well as in all breaks during morning lessons (duration 4.5 hours). Water intake was documented and categorized into 4 groups: 1: 0 < 500 ml (n = 23); 2: 500 < 1000 ml (n = 82); 3: 1000 < 1500 ml (n = 73); 4: ≥ 1500 ml (n = 71). Cognition was tested once via a computer-based task-battery in classes during lunch break (12:30 pm). Four cognitive parameters were examined: working memory (2-back task), cognitive flexibility (Switch task), visual-spatial memory (Corsi block task) and inhibitory control (Flanker Task). Statistical analyses were performed using one-way ANOVA for normally distributed parameter and Kruskal-Wallis test for non-normally distributed data. Interrelations between water uptake and cognitive performance were calculated using Spearman correlation.

Results: Groups of categorized water intake showed significant differences with regard to reaction time (RT) of visual search letters (p = 0.003). Up to 1000 ml water RT decreased from 76 to 63 seconds (category 1 vs. 3 p = 0.04) and subsequently increased again to 73 seconds (category 3 vs. 4 p = 0.04). Further analyses confirmed a correlation up to 1000 ml water for Switch task (p = 0.002), for 2-back task in the ratio of missings (p = 0.02), and for Corsi block task in the longest correct path (p = 0.03)

Discussion: Single cognitive parameters are positively influenced by an increased water intake. More specifically, a quantity of 1000 ml seems to be sufficient for schoolchildren throughout the morning, at least in our study setting.

Conclusion: This study shows that children are profiting from an increased, short-term water intake with regard to their cognitive performance. Further studies should aim at long-term implementations to promote water supply in schools.

Funding: Funded by Uniscientia Foundation, Vaduz.

No conflict of interest has been declared by the author(s).