Out-of-Synch Body Clocks and Bedtime-Resistant Children

Putting a child to bed for the night only to see them reappear from the bedroom minutes later asking for a glass or water, a bathroom trip or just one more story may be a common experience for countless parents and babysitters around the world. But a new study published in the journal Mind, Brain and Education suggests that when this happens it may be a result of the child's bedtime being out of synch with his or her internal body clock.

The research is noteworthy, as about 25 percent of toddlers and preschoolers have problems settling down after going to bed, said Monique LeBourgeois, an assistant professor at University of Colorado Boulder who contributed to the research.

The study pinpointed the time when the hormone melatonin increases during the evening, which is the biological indicator that the night has begun and it's time for bed.

LeBourgeois and her colleagues learned that toddlers with a longer interval between the nightly onset of melatonin release and their subsequent bedtimes fell asleep more quickly and had less "bedtime resistance."

The research followed a group of 14 toddlers whose sleep was studied for six days.

In addition to being an annoyance for caregivers looking for a few hours of quiet time in the evening, sleep problems in early childhood are predictive of later emotional and behavioral problems and poor cognitive function than can persist into adolescence, the researchers said in a statement.

Furthermore, caregivers of children with sleep problems often reported increased difficulties in their own sleep patterns, which can cause chronic fatigue or even marital discord, LeBourgeois 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.

The average melatonin onset for the toddlers in the study was 7:30 p.m., about 30 minutes prior to the child's normal, parent-selected bedtime. After being put to bed, it took the toddlers about 30 minutes to fall asleep.

Toddlers who were put to bed before their natural melatonin rise 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," LeBourgeois said. "This type of response may increase children's lifelong risk for insomnia over time."

"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."