Influence of light at night on melatonin suppression in children
Shigekazu Higuchi1, Yuki Nagafuchi, Sang-il Lee
1Department of Human Science (S.H., Y.N., S.L.), Faculty of Design, Kyushu University, Fukuoka 815-8540, Japan; and Laboratory of Environmental Physiology (T.H.), Faculty of Education, Kochi University, Kochi 780-8520, Japan.
Insights
Children exhibit nearly double the melatonin suppression in response to light compared to adults, indicating heightened light sensitivity in pediatric melatonin regulation. This suggests children
Area of Science:
- Chronobiology
- Pediatric Endocrinology
- Ophthalmology
Background:
- Children's larger pupils and clearer lenses suggest higher melatonin sensitivity to light.
- However, empirical data on light-induced melatonin suppression in children is limited.
Purpose of the Study:
- To compare light-induced melatonin suppression between healthy children and adults.
- To determine if children exhibit greater sensitivity to light's effect on melatonin.
Main Methods:
- Two experiments involving 33 children (mean age 9.2 years) and 29 adults (mean age 41.6 years).
- Salivary melatonin levels and pupil diameter measured under varying light conditions (dim, moderate, room light).
Main Results:
- Moderately bright light significantly suppressed melatonin in both groups.
- Melatonin suppression was significantly greater in children (88.2%) than adults (46.3%).
- Room light at home suppressed melatonin in children but not in adults.
Conclusions:
- Children's melatonin is nearly twice as suppressed by light compared to adults.
- This suggests melatonin is more sensitive to light exposure in children at night.
Context:
The sensitivity of melatonin to light suppression is expected to be higher in children because children have large pupils and pure crystal lenses. However, melatonin suppression by light in children remains unclear.
Objective:
We investigated whether light-induced melatonin suppression in children is larger than that in adults.
Methods:
Thirty-three healthy primary school children (mean age, 9.2 ± 1.5 y) and 29 healthy adults (mean age, 41.6 ± 4.7 y) participated in two experiments. In the first experiment, salivary melatonin concentrations in 13 children and 13 adults were measured at night under a dim light (<30 lux) and a moderately bright light (580 lux) in an experimental facility. Pupil diameters were also measured under dim light and bright light. In the second experiment, melatonin concentrations in 20 children and 16 adults were measured under dim light in the experimental facility and under room light at home (illuminance, 140.0 ± 82.7 lux).
Results:
In experiment 1, the melatonin concentration was significantly decreased by exposure to moderately bright light in both adults and children. Melatonin suppression was significantly larger in children (88.2%; n = 5) than in adults (46.3%; n = 6; P < .01), although the data for some participants were excluded because melatonin concentrations had not yet risen. In experiment 2, melatonin secretion was significantly suppressed by room light at home in children (n = 15; P < .05) but not in adults (n = 11).
Conclusion:
We found that the percentage of melatonin suppression by light in children was almost twice that in adults, suggesting that melatonin is more sensitive to light in children than in adults at night.
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