Putting toddlers to bed at a specified time may put them out of sync with their internal body clocks, making it difficult for them to fall asleep, according to a new University of Colorado Boulder study.
In a group of 14 toddlers, researchers pinpointed the time when the hormone melatonin spiked in the evening, indicating the start of the biological night. The findings showed that toddlers with later melatonin rise times took longer to fall asleep after being put to bed, said CU-Boulder Assistant Professor Monique LeBourgeois, Ph,D.
“There is relatively little research out there on how the physiology of toddlers may contribute to the emergence of sleep problems,” said study leader LeBourgeois.
“Sleeping at the wrong ‘biological clock’ time leads to sleep difficulties, like insomnia, in adults.”
Although adults can choose when they go to sleep, toddlers rarely have this option, said LeBourgeois.
“This study is the first to show that a poor fit between bedtimes selected by the parents of toddlers and the rise in their evening melatonin production increases their likelihood of nighttime settling difficulties,” said LeBourgeois.
About 25 percent of young children have difficulty settling down after bedtime, said LeBourgeois. Problems may include having trouble falling asleep, bedtime resistance, tantrums, and episodes known as “curtain calls,” such as calling out from bed or coming out of the bedroom, often repeatedly, for another story, glass of water or bathroom trip, she said.
Toddlers with longer intervals between the onset of nightly melatonin release and their bedtimes were shown to fall asleep more quickly and had decreased bedtime resistance as reported by their parents, according to the study.
Sleep difficulties in early childhood are predictive of later emotional and behavioral problems, as well as poor cognitive function, that can persist into later childhood and adolescence. And parents of young children with sleep problems often report increased difficulties in their own sleep patterns, which can cause chronic fatigue and even marital discord, she said.
“A natural next step is to optimize our knowledge of the interactions between physiology and the environment to further understand how problems like bedtime resistance first develop and how they are maintained,” LeBourgeois said.
Prior research in adolescents and adults has shown that exposure to light in the evening can delay the onset of melatonin. Whether the later rise of melatonin in some toddlers can be pushed to an earlier time by restricting evening light or by increasing morning light exposure is a question still to be answered, she said.
“We believe that arming parents with knowledge about the biological clock can help them make optimal choices about their child’s activities before bedtime, at bedtime, and his or her sleeping environment,” LeBourgeois said.
The typical melatonin onset for the toddlers occurred at roughly 7:40 p.m., about 30 minutes before parent-selected bedtimes, said LeBourgeois. On average, the toddlers fell asleep about 30 minutes after bedtime.
“It’s not practical to assess melatonin levels in every child,” LeBourgeois said. “But if your child is resisting bedtime or having problems falling asleep, it is likely he or she is not physiologically ready for sleep at that time.”
During the study, toddlers who were put to bed before their rise in melatonin took 40-60 minutes to fall asleep.
“For these toddlers, laying in bed awake for such a long time can lead to the association of bed with arousal, not sleep,” she said. “This type of response may increase children’s lifelong risk for insomnia over time.”
Source: University of Colorado Boulder