LINDA WERTHEIMER, HOST:
A good night's sleep is important for everybody but a regular bedtime is especially important for kids. Michelle Trudeau reports on a new study which confirms everything your mother ever told you about going to bed on time.
KAREN RABIN: Come on, Phee. Let's get to bed. Put your toys away.
MICHELLE TRUDEAU, BYLINE: A typical scene: Karen Rabin getting her 7-year old to bed. Its 7:30, a school night. The bedtime rituals are underway.
RABIN: Did you go to the bathroom?
PHEE: Yeah.
RABIN: Did you drink water?
PHEE: Yeah.
TRUDEAU: Researcher Yvonne Kelly, from University College, London, has been studying all the tiny details surrounding bedtime in thousands of homes in the U.K.
DR. YVONNE KELLY: We looked at over 10,000 children from a large population-based survey.
TRUDEAU: Each child was studied at age 3 then at age 5, and again at 7.
KELLY: We took information about their bedtimes and their behaviors throughout their early childhood period.
TRUDEAU: And what Kelly uncovered reinforces what many parents know intuitively.
KELLY: Children with late bedtimes and non-regular bedtimes were more likely to have behavioral difficulties.
TRUDEAU: What kind of difficulties?
KELLY: You know, things to do with hyperactivity and conduct problems. So hitting people and acting out, and not getting on with peers, and being emotionally withdrawn.
TRUDEAU: Even after taking into account a whole slew of differences between families - income, number of children, amount of TV-watching, whether the child ate breakfast, etcetera, etcetera. In spite of family differences, having an irregular bedtime affected behavior most strongly. Even having more of an impact on behavior than a late bedtime.
Kelly thinks young children probably experience an inconsistent bedtime like having jet-lag.
KELLY: If you change their bedtimes, say, 7 o'clock one night, 9 o'clock, the next, 8 o'clock the next, 10 o'clock the next, if we do too much of that switching, we end up inducing this kind of jet-lag effect, which makes it really, really difficult to regulate behavior.
TRUDEAU: This because of the power of that master biological clock deep inside the brain, the suprachiasmatic nucleus. This tiny cluster of nerve cells, no bigger than a grain of rice, is super-sensitive to sunlight and other light coming in through our eyes. At the end of the day, when the ambient light starts to fade, a brain hormone called melatonin starts to rise, causing drowsiness.
Sleep researcher Russell Rosenberg says that children have this rise in melatonin much earlier in the evening than say, teenagers or adults. And that the natural time for young children to fall asleep is somewhere between 7 and 8 p.m. So, advises Rosenberg, it's really important to start turning off light sources, such as all those electronics, a half hour or so before the desired bedtime.
RUSSELL ROSENBERG: The light exposure from either a television screen or a computer screen can have an impact on suppressing melatonin. You know, you don't want melatonin suppression as the child is getting ready for bed.
TRUDEAU: Every parent knows getting kids to bed on time isn't easy - what, with busy, complicated lives. But there's also some encouragement coming from Dr. Kelly's study: the behavior problems were reversible. Children who switched from having an irregular bedtime to a regular bedtime, their behaviors improved.
So, whenever possible, the researchers suggest, try to get your child into a bedtime routine: all electronics off, bath-time, brushing teeth time, book time.
RABIN: Do you want to read or do you want me to read?
PHEE: I can read one chapter, and then...
RABIN: OK. We're just going to read one chapter. But you start and then I'll finish-up.
PHEE: OK. (Reading) One summer day in Frog Creek, Pennsylvania...
TRUDEAU: Young children need eight to nine hours of sleep every night. Not always possible, but that's the goal.
RABIN: Good job, Phee.
(SOUNDBITE OF KISS)
RABIN: I'll see you in the morning.
PHEE: OK.
TRUDEAU: For NPR News, I'm Michelle Trudeau.
(SOUNDBITE OF MUSIC)
WERTHEIMER: It's MORNING EDITION from NPR News. Transcript provided by NPR, Copyright NPR.