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Seasonal changes in hydration in free-living Japanese children and adolescents
Tatsuro Amano1, Kotaro Sato1, Junto Otsuka1
1Laboratory for Exercise and Environmental Physiology, Faculty of Education, Niigata University, Niigata, Japan.
Insights
Many Japanese children experience underhydration, particularly in spring. Self-assessed urine color (UC) is unreliable for monitoring hydration status in children, as they cannot detect seasonal changes. Urine osmolality (Uosm) is a more accurate measure.
Area of Science:
- Pediatric Health
- Human Physiology
- Nutritional Science
Background:
- Hydration status fluctuates daily, impacting physiological and behavioral functions.
- Limited data exists on the hydration status of free-living Japanese children and its seasonal variations.
- Understanding children's hydration is crucial for their overall health and well-being.
Purpose of the Study:
- To evaluate the hydration status of Japanese children using urine osmolality (Uosm).
- To investigate the seasonal differences in hydration status among Japanese children.
- To assess the effectiveness of self-assessed urine color (UC) as a hydration monitoring tool for children.
Main Methods:
- Studied 349 Japanese children (ages 6-15) in spring and summer.
- Measured hydration status via urine osmolality (Uosm) upon waking and during the school day.
- Assessed children's self-reported urine color (UC) using an 8-point scale.
Main Results:
- Higher Uosm (indicating underhydration) was observed in spring compared to summer upon waking.
- No significant Uosm differences were found during the school day between seasons.
- A substantial percentage of children were underhydrated upon waking (66% in spring, 50% in summer), with a smaller percentage (approx. 12%) underhydrated during the school day.
- Self-assessed urine color (UC) did not reflect seasonal hydration changes, unlike Uosm.
Conclusions:
- A significant number of Japanese children are likely underhydrated, especially during spring.
- Self-assessed urine color is not a reliable indicator for monitoring hydration status in children due to their inability to perceive seasonal changes.
- Urine osmolality is a more accurate method for assessing hydration status in pediatric populations.
Abstract:
Changes in hydration status occur throughout the day affecting physiological and behavioural functions. However, little is known about the hydration status of free-living Japanese children and the seasonality of this response. We evaluated hydration status estimated by urine osmolality (Uosm) in 349 children (189 boys and 160 girls, 9.5 ± 2.6 years, range: 6-15 years) upon waking at home and during a single school day in spring (April) and summer (July). Further, we assessed the efficacy of employing self-assessment of urine colour (UC; based on an 8-point scale) by children to monitor their hydration status. Early morning Uosm was greater in the spring (903 ± 220 mOsm L-1; n = 326) as compared to summer (800 ± 244 mOsm L-1; n = 125) (P = 0.003, paired t test, n = 104). No differences, however, were observed in Uosm during the school day (P = 0.417, paired t test, n = 32). While 66% and 50% of children were considered underhydrated (Uosm ≥ 800 mOsm L-1) upon waking in the spring and summer periods, respectively, more children were underhydrated (∼12%) during the school day. Self-reported UC was similar between seasons as assessed in the morning and school day (P ≥ 0.101, paired t test), which differed from the pattern of responses observed with Uosm. We showed that a significant number of Japanese children are likely underhydrated especially in the spring period. Children do not detect seasonal changes in hydration from self-assessed UC, limiting its utility to manage hydration status in children.
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