Body clock may be to blame when tots fight sleep

Body clock may be to blame when tots fight sleep

December 31st, 2013 in Local - Breaking News


AP Medical Writer

WASHINGTON - "Just one more story, please?" ''I need a glass of water." ''Mom, I can't sleep!"


That doesn't mean tots should be up at all hours.

"Just like nutrition and exercise, sleep is critical for good health," said sleep scientist Monique LeBourgeois of the University of Colorado, Boulder, who is leading the research.


We all have what's called a circadian rhythm, a master biological clock, that regulates when we become sleepy, and when we're more alert. Those patterns vary with age: It's the reason teenagers are notorious for late nights and difficult-to-wake mornings.



Then on the last afternoon, researchers visited each home, dimming lights and covering windows. Then every 30 minutes for six hours leading up to the child's appointed bedtime, they also coaxed each tot to chew on some dental cotton to provide a sample of saliva.

The reason: To test for levels of a hormone named melatonin that is key to the sleep cycle and also sensitive to light. At some point every evening, people's melatonin levels surge and a while later, they begin to feel sleepy. Among adults who sleep well, that melatonin rise tends to happen about two hours before whatever is their chosen bedtime.




"We don't know what that sweet spot is yet," LeBourgeois said, but the data suggest bedtime is easiest if the melatonin surge occurred at least 30 minutes earlier.

The study reinforces what doctors have long suspected is one bedtime barrier, said Dr. Jyoti Krishna, a pediatric sleep expert at the Cleveland Clinic. Other factors can disrupt a child's sleep, too, such as noise, stress or anxiety, or disrupted home routines, he cautioned.

"But this paper reminds us that, hey, there is a time that the body is more ready to sleep than at other times," Krishna said.


Parents don't have melatonin tests as a guide, so Krishna advises looking for cues when setting a bedtime -- yawning, rubbing eyes -- and then to adjust that bedtime as the child gets older.

"The melatonin onset and our body rhythms change," Krishna said. "You can't stick to what worked two years ago with this child, because this child is now a different child."

About 25 percent of young children experience some type of sleep difficulty, including trouble settling down at bedtime, LeBourgeois said. Harried parents aside, there's concern that early-in-life bedtime frustration might lead to more persistent sleep trouble.

"Listen to your child's physiology," she advised. Some steps that might help:

--Research shows that in adults, too much light in the evening delays the melatonin surge and subsequent sleepiness. While there's no data in young children yet, LeBourgeois says dimming the lights about an hour before bedtime makes sense.


--And make sure blackout shades aren't keeping your children from getting enough morning sunlight, she said. Light in the morning also is key to keeping the biological sleep clock on schedule.

Stay tuned: With funding from the National Institute of Mental Health, LeBourgeois has begun a larger study that will track sleep patterns of 40 2-year-olds until they're 5. She'll also measure their light exposure, and periodically record their brain waves during sleep, in a bid to better understand the influence of sleep patterns on children's development.