Establishing healthy bedtime habits for your child early on is vital if at least one parent has chronic sleep difficulties, suggests new research on genetics and children's sleep disorders.
A genetic predisposition for sleep problems such as insomnia has been found repeatedly in studies of adults, leaving scientists wondering whether the same phenomenon occurs among children.
It does, say experts behind the first study providing evidence that genetic susceptibility to being a "poor sleeper" can also be found early in life.
Children genetically predisposed to insomnia had more insomnia-related sleep issues such as difficulty falling asleep or frequently waking up during the night, according to the study published Wednesday in the Journal of Child Psychology and Psychiatry.
The findings may "be surprising for most people," said senior author Dr Eus van Someren, head of the department of sleep and cognition at the Netherlands Institute for Neuroscience in Amsterdam, via email. "We tend to think that insomnia develops later in life, but here we clearly show that the earliest signs of the risk of insomnia in adulthood are present already in early childhood."
A genetic predisposition to sleep issues is only part of the puzzle, however, so maintaining your child's sleep hygiene can still make a difference, experts said.
Assessing sleeplessness in kids
The authors studied 2458 European children, about half of whom were girls, involved in the Generation R study, which recruited pregnant women with a due date between 2002 and 2006 so their children's health could be measured from fetal life through adulthood. In the Generation R study, experts collected DNA samples from blood of the umbilical cord or from the children when they were six years old.
When the children were ages one-and-a-half, three, six, and between 10 and 15, their mothers shared details on their sleep health - such as whether they had trouble falling asleep, slept less than most children or often woke up throughout the night. Some participants - 975 of them - also wore sleep-tracking watches for nine days twice between ages 10 and 15.
The authors found a genetic predisposition to the development of insomnia in kids was associated with insomnia-like symptoms reported by their mothers, but those symptoms weren't detected by the sleep trackers, which are more objective.
That could be because sometimes some people - in this case the study mothers tracking their kids' sleep - have the perception of insomnia even when they're not actually lacking sleep in terms of quantity, said Dr Amita Sehgal, director of the Chronobiology and Sleep Institute of the University of Pennsylvania Perelman School of Medicine, who wasn't involved in the study. The quality of sleep may just not be sufficiently restful.
Being genetically predisposed to sleeping longer, however, was related to sleeping three minutes more on average by the tracker's objective measurement - but three more minutes of rest for study participants went along with also waking up for less than one minute total during the night.
"It wasn't a surprise to me that there is a genetic determination of sleep in children as there is in adults," said Sehgal, who is also a professor of neuroscience at the University of Pennsylvania Perelman School of Medicine. "You would think that, sure, if it's genetically determined, why wouldn't it manifest earlier in life?"
Good sleep hygiene for kids
There is still hope for your child's sleep health.
More studies are needed to identify the processes underlying the findings, "alongside genetic predisposition for other behavioral and psychiatric traits," said the study's first author Dr Desana Kocevska, a sleep scientist in the department of child and adolescent psychiatry at Erasmus Medical Center in Rotterdam, the Netherlands, via email.
But since "the results of our study may indicate that children of parents who sleep poorly may be particularly vulnerable for sleep problems," Kocevska said, "sleep hygiene practices from an early age may be especially important for this group."
As much as you can, try to ensure they've finished eating a few hours before bedtime and darken their bedroom as much as they're comfortable with when they go to sleep, Sehgal said.
Your child's circadian rhythm
Also pay attention to what your child's personal circadian rhythm seems to be, she added, such as when they're typically most awake or ready to fall asleep.
"If your child is a natural late sleeper, then don't force them to go to sleep early," Sehgal added.
If "in the morning they're sleeping in and it's hard to wake them up, then their internal circadian rhythm is probably delayed. And rather than fight that, you try to accommodate that," she explained.
This flexibility is generally only feasible before school-age years, when school start times aren't in harmony with minors' circadian rhythms, Sehgal acknowledged.
"Something that we in the circadian field have been fighting for a long time is (that) the school timings are all wrong," she said.
When to take your child to a sleep specialist
Though elementary-age children tend to wake up early and adolescents sleep late, elementary children start school later in the day while middle and high schoolers start very early.
Policy changes would be helpful for parents and caregivers trying to manage their children's sleep health based on what their bodies need at the time.
When your child should see a specialist depends on how bad the problem is, Sehgal said.
"Is this something you can live with? Is the child functioning? Do they seem happy otherwise? Are they doing OK academically, socially?" she added. "Maybe then you don't have to do too much. But if not, then yes."