Nap time: Research looks at toddlers' sleep patterns

Anyone who has cared for toddlers knows many mysteries lurk in the 2- and 3-year-old brain. One of the biggest mysteries concerns their sleep.

Missouri State law requires day cares give toddlers a two-hour nap time each day.

"At this age -- 4 to 4 1/2 -- they start to outgrow it," said Niki Siebert, a teacher at Cape Girardeau Montessori School. She said as long as the children lay down and are quiet, the staff does not always make them sleep, though the nap is beneficial.

"You can tell that they're really tired, that they do need their nap," Siebert said.

Lloyd Diamond, a registered sleep technician with Sleep Analysts Inc. in Cape Girardeau, said toddlers need 12 to 14 hours of sleep in a 24-hour period.

"When you sleep, that's when your body restores itself," Diamond said.

More blood supply reaches parts of the body than when you're awake. Diamond said that restoration is important. "Especially with somebody who's young and developing."

The biological processes that determine when and how much a preschooler sleeps, or what happens when she doesn't sleep enough are largely undocumented.

A research professor at Brown University, Monique K. LeBourgeois and two assistants have been visiting families in their homes trying to gather more information. They use games and toys to keep the toddler awake and measure the results. Their laboratory consists of portable file boxes and computer-stuffed backpacks; their skills include clay sculpture and cuddling.

With grants from the National Institute of Mental Health and drug-maker Sepracor, LeBourgeois is studying how skipping or delaying a nap -- they call it "nap deprivation" -- changes youngsters' behavior and emotions.

From 2 to 5 years old, children's sleep patterns reorganize, making the transition from napping to staying awake all day. Preschools and kindergartens are questioning whether to replace naptime with more learning. But does skipping a nap affect a child's ability to learn?

"[LeBourgeois[']s] research will give us the first peek into what's going on at this development stage with how the brain is trying to organize sleep," says Mary A. Carskadon, director of the Bradley Hospital Sleep and Chronobiology Research Lab. "That will help us understand more about how parents should be viewing sleep and helping their children manage sleep at this young age."

The researchers gather a spit sample from the participating toddler by having them chew a flavored cotton roll.

The saliva, collected on many occasions throughout the study, is analyzed for levels of the hormone melatonin. An increase in melatonin makes it easier to fall asleep and indicates that the brain's "clock" -- the internal system that regulates sleeping and waking -- is moving its hands toward nighttime. At other times, the saliva will be tested for levels of cortisol, a hormone released at times of stress.

Early results showed as much as two hour variations in the time of day when melatonin levels started to rise. All tended to have melatonin boosts at least two hours earlier than adults or adolescents.

On five days during the study, the researchers manipulate sleep times by keeping the children stimulated with activities through naptime or past the usual bedtime. Then they put the children to sleep with electrodes attached to the scalp, face, shoulder and side.

They measure brain waves, eye movements, muscle activity and heartbeat while the child sleeps -- patterns that reveal the intensity of the body's "hunger" for sleep. The study also measures emotional reactions after they've stayed awake through their naptime.

LeBourgeois has observed a surprising phenomenon with the first few children in the study. Instead of the "tired and wired" meltdowns familiar to parents of napless toddlers, the children look quiet and sad, with blunted emotions.

"They're not engaged; they're withdrawn," LeBourgeois said.

LeBourgeois has not yet analyzed her data, but she hopes the results will shed light on the role of sleep in emotional development. An estimated 7 to 23 percent of preschool children have emotional or behavioral problems.

Staff writer Chris Harris contributed to this article, which originally appeared in the Providence Journal.