How much does light exposure affect melatonin levels? A new study suggests that late-day exposure may lower levels significantly (Akacem, Wright and LeBourgeois, Physiological Reports, March 4, 2018).
Evening Light and Melatonin Levels:
Young children exposed to bright light before bedtime may not make normal levels of the sleep-associated hormone melatonin when they are tucked in. Researchers studied ten healthy preschoolers. For the first five days, the youngsters followed a normal bedtime schedule. On the sixth evening, the investigators dimmed the lights in their homes. The lights remained low throughout the following day.
The scientists took periodic saliva samples to measure melatonin levels. On the seventh evening, the youngsters played with colored tiles or crayons and paper on a bright light table for an hour.
Compared to the low-light evening, kids’ melatonin levels were 88 percent lower after light exposure. These low levels lasted at least 50 minutes after the lights were turned off.
Will Bright Lights at Night Change Children’s Sleep Patterns?
The researchers are concerned that exposure to bright evening light might disrupt young children’s circadian rhythms and sleep patterns. (A different study would be needed to determine how frequently this is the primary problem for children who don’t sleep well.) Health professionals might use these findings to make evidence-based recommendations for parents to get little kids settled for the night. The link the scientists found between evening bright light exposure and lower melatonin levels may be useful “in preventing the development of late sleep timing in the early years of life.”
