Long-Term Effects of Drinking Water and Sweetened Beverages on Cognition of Schoolchildren – CogniDROP-II Study

OBJECTIVES: Adequate fluid intake is essential for cognition. Our previous short-term motivational intervention study (CogniDROP I) showed that a water intake of 0.5–1.5 l in the morning had positive effects on selected parameters of cognition in schoolchildren. The aim of this CogniDROP II study was to determine whether long-term motivation also leads to more water consumption and how this affects cognition. METHODS: 270 children (grades 5 & 6) from a comprehensive school in Germany participated in the randomized intervention trial. Children from 7 intervention classes were motivated by teaching staff to drink water during class breaks for 12 weeks; children from control classes were not. Drinking habits (drinking amount at school, type of drink) were recorded at the beginning and end of the study. At these time points, computer-based cognitive testing was performed for selective attention (switch task), working memory (2-back), visuospatial memory (corsi block), and inhibitory control (flanker). Analysis was performed using a general linear model (GLM) with repeated measures. RESULTS: The intervention did not increase water consumption in intervention classes (0.88 ± 0.55 l vs. 1.0 ± 0.67 l) compared to control classes (1.09 ± 0.9 l vs. 1.12 ± 0.77 l). Accordingly, apart from a shorter reaction time for task switching in the intervention group (83.9 ± 23.0 s vs. 88.7 ± 25.4 s; p = 0.04), no differences in cognition were observed. However, children who did not exclusively drink water at school but also sweetened beverages made more errors in the flanker (p = 0.03) and 2-back (p = 0.004) and showed poorer visuospatial memory. CONCLUSIONS: Long-term motivation of children to drink water is a major challenge, as is the assessment of their drinking habits at school. Therefore, no firm conclusions can be drawn from this study as to whether water consumption affects the cognition of schoolchildren in the long term. However, the type of beverage might play a role. FUNDING SOURCES: Uniscientia Foundation, Vaduz, Liechtenstein