How the Internal Clock Affects Children's Health | Natural Health Blog

Date: 01/04/2014    Written by: Beth Levine

Your Toddler’s Internal Clock

How the Internal Clock Affects Children's Health | Natural Health Blog

Most parents of toddlers set their child's bedtime at a fairly early hour, correctly reasoning that children this young need to be getting quite a bit of sleep.  Of course, it doesn't hurt that it also gives the parents a few child-free hours in the evening to get things done or just relax for a while.  But this downtime can deteriorate very quickly when your toddler won't actually go to sleep at bedtime.  And now researchers may have an answer as to why this occurs: sometimes parents choose the wrong bedtime for their child's particular internal clock, potentially jeopardizing their children's health.

The study, which took place at the University of Colorado Boulder, found that children's individual melatonin levels are what dictate when they are truly ready to fall asleep, and an arbitrary bedtime set by parents merely fights against this fact.1  Just as many adults are by nature morning larks or night owls, even little kids have some variation in when they become tired enough to start settling down for the night.  The subjects were 14 children between the ages of 30 and 36 months and their families, all of whom lived in Providence, Rhode Island.  Each child had a pattern of sleeping for a minimum of 10.5 hours per night and taking a daytime nap that lasted at least 45 minutes.

The researchers collected saliva samples from the youngsters every half hour over the course of six hours prior to their standard bedtime on one day of the six-day experiment.  They used these samples to measure melatonin levels in the participants.  By determining exactly when the melatonin began to rise in the evening, the scientists could pinpoint when the children's individual biological clocks were telling them it was nighttime.  This is important because if the parent-selected bedtime does not mesh with the child's internal clock, it can set the stage for long-term sleep issues that can damage children's health.

While this study is extremely small, these findings may nevertheless help explain why so many toddlers give their parents a hard time when bedtime rolls around.  The kids may lay in bed without falling asleep, become resistant to getting into bed, throw tantrums, call out to mom and dad from bed, or leave their rooms several times to prolong bedtime.  And when these kinds of problems develop and are not resolved, they can result in emotional difficulties, behavioral issues, and impact cognitive abilities--and they can also stay with the child for many years. A 2013 study at the University of Virginia, Charlottesville, determined that preschoolers who slept for shorter overnight durations experienced a greater likelihood of displaying impulsivity, aggression, and angry behavior than their peers who were sleeping better.2

In the current research, the scientists found that those children who were given a longer interval between when their melatonin levels began to elevate and the time they were actually tucked in for the night tended to fall asleep faster, experience less stress and anxiety, and offer less resistance at bedtime than the children with shorter intervals, according to the information provided by their parents. The average rise in melatonin occurred around 7:40 p.m., which was typically about 30 minutes prior to bedtime.  However, those youngsters who had a bedtime earlier than their melatonin increase often did not fall sleep for 40 to 60 minutes past bedtime.  That's not pleasant for the poor toddler laying in the darkness before sleepiness sets in or for the parents who often can't understand why their little one is being so difficult.

So what can you do if your toddler appears to be plagued by bedtime problems and is continually calling or getting out of bed?  Just as older kids and adults have been shown in a 2011 National Sleep Foundation study to mess up their internal clocks because of too much screen time close to bed, the same most likely holds true for very young children.  Since melatonin rises in the dark, the artificial light from a television or video game screen may be the delaying factor.3 You can spend quality time with your toddler reading books, playing a game, or taking part in some other relatively calm pursuit that does not involve starting at a brightly lit screen and everyone will get much more out of this time than you would struggling over a bedtime war.

  • 1. "Bedtime for Toddlers: Timing is Everything." Science Daily. 16 December 2013. Accessed 23 December 2013.
  • 2. Scharf, Rebecca J.; et al. "Nighttime Sleep Duration and Externalizing Behaviors of Preschool Children." Journal of Developmental Behavioral Pediatrics. July/August 2013. Accessed 24 December 2013.
  • 3. "Annual Sleep in America Poll Exploring Connections with Communications Technology Use and Sleep." National Sleep Foundation. 7 March 2011. Accessed 24 December 2013.

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