Hydration, mood, and cognition in primary school aged children in the United Kingdom

Effective cognition is fundamental to academic attainment and has been linked to multiple dietary behaviours, including adequate hydration. This study aimed to evaluate whether the hydration status of primary school children (9-10y) across the school day was associated with cognition and mood. Food and fluid intake were tracked using photographic dietary records. Urine/serum osmolality (Uosm/Sosm), urine specific gravity (USG) and self-reported urine colour (Ucol) were assessed at first void (Uosm only) or the start (09:00) and end (16:00-16:30) of the school day. Children’s self-reported mood and appetite were obtained via Visual Analogue Scales (VAS at 09:00, 10:30, 13:30 and 16:00). Children completed cognitive assessments using the Computerised Mental Performance Assessment System (15:30-16:00). T-tests indicated that (a) children consumed most fluid at mealtimes (P < 0.001), and (b) Sosm, USG and Ucol increased (P < 0.01) throughout the school day, indicating a shift towards dehydration. Additionally, from the start to the end of the day, feelings of boredom, hunger, tiredness, and thirst increased, whereas focus and happiness decreased (P < 0.05). Hydration measures were significantly associated with long-term (P = 0.042) and working memory (P = 0.033). Despite access to ad-libitum water, this study indicates primary age school children do not maintain hydration status during the school day. This suggests interventions to improve hydration status in the primary school setting should focus on increasing water intake and/or retention of ingested water throughout the day.