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Thermoregulation during heat exposure of young children compared to their mothers
K Tsuzuki-Hayakawa1, Y Tochihara, T Ohnaka
1Human Environment System Department, National Institute of Bioscience and Human-Technology, Tsukuba, Japan.
Insights
Young children heat up faster than adults due to smaller body size, despite a higher surface area-to-mass ratio. Their thermoregulation is less effective during heat exposure, indicating maturation-related differences.
Area of Science:
- Environmental Physiology
- Pediatric Thermoregulation
Background:
- Thermoregulation is critical for maintaining homeostasis, especially in vulnerable populations like young children.
- Understanding age-related differences in heat response is essential for public health and safety.
Purpose of the Study:
- To investigate and compare the thermoregulation of young children and adults under controlled heat exposure.
- To identify potential maturation-related differences in physiological responses to heat stress.
Main Methods:
- 19 children (9 months-4.5 years) and 16 adults were exposed to thermoneutral and hot environments.
- Measurements included rectal temperature (Tre), skin temperatures (Tsk), heart rate (HR), and sweat rates (Msw,t, Msw,l).
- Sweat sodium (Na+) concentration was also analyzed.
Main Results:
- Children exhibited significantly higher rectal temperatures (Tre) than adults during heat exposure.
- Children had higher mean skin temperatures (Tsk) and higher total sweat rates (Msw,t).
- Despite a greater body surface area-to-mass ratio, children's responses were insufficient to prevent increased body temperature.
Conclusions:
- Young children heat up more easily than adults due to smaller body size, despite physiological adaptations.
- Thermoregulation during heat exposure shows maturation-related differences between young children and adults.
- Children's thermoregulatory responses may be less efficient, highlighting a potential disadvantage in hot environments.
Abstract:
The study was conducted to investigate the thermoregulation of young children compared to that of adults. A group of 19 children (ages 9 months-4.5 years), with only 3 children aged 3 years or above, and 16 adults first rested in a thermoneutral room (air temperature 25 degrees C relative humidity 50%, air velocity 0.2 m.s(-1)). They were then exposed to a hot room (air temperature 35 degrees C, relative humidity 70%, air velocity 0.3 m.s(-1)) next door for 30 min, and then returned to the thermoneutral room where they stayed for a further 30 min. The rectal temperature (Tre), skin temperatures (Tsk) at seven sites, heart rate (HR), total sweat rate (Msw,t), local sweat rate (Msw,l) and the Na+ concentration of the sweat were measured. There was no significant difference in Tre between the children and their mothers in the rest phase. However, the Tre of the children increased as soon as they entered the hot room and was significantly higher than during the control period, and than that of the mothers during heat exposure. Mean Tsk, forehead, abdomen and instep Tsk were significantly higher in the children during both the thermoneutral and heat exposure. The Msw,t was significantly higher and Na+ concentrations in the sweat on the back and upperarm were significantly lower for the children during the heat exposure. They had a greater body surface area-to-mass ratio than the mothers by 64%, which indicated that they had advantages for thermal regulation. However, the sweating and Tsk responses of the children were not enough to prevent a rise in body temperature. These results would suggest that the young children had the disadvantage of heating up easily due to their smaller body sizes and there may be maturation-related differences in thermoregulation during the heat exposure between young children and mothers.