Q: My almost 5-year-old son is very tired during the day, even though he gets 10 hours of sleep most nights. He is in school now, so he can’t take daily naps. I’ve noticed that he kicks a lot during the night. Should I look into another cause, like periodic limb movement disorder? — Via e-mail

A: By age 5, most children no longer need naps, so not napping is unlikely to explain the fatigue. Ten hours of sleep is enough for most children his age, although the necessary amount varies from child to child.

So sleep quality may indeed be the problem. A number of disorders can disturb a good night’s sleep, including narcolepsy and obstructive sleep apnea, which is commonly caused by allergies, asthma and obesity.

Periodic limb movement disorder is another cause to consider when a child (or adult) kicks or moves his legs while asleep and is tired during the day. (Certain kinds of seizures can also cause unusual movement during sleep.)

Child sleep experts Dr. Judy Owens and Dr. Jodi Mindell note that PLMD is often missed because the symptoms are not reported. Also, many doctors don’t know about this condition. PLMD is relatively common in adults, especially as they age. But not until recently has the condition been recognized in children.

Your pediatrician could refer you a pediatric sleep specialist who can conduct a sleep study, make a diagnosis and recommend treatment.

Such a study is carried out in a sleep lab (usually in a hospital), where the child spends the night — and where a parent should be encouraged to stay, too.

The lab monitors and records the child’s heart rate, blood pressure, breathing rate, movements and brain waves through the night.

A child with PLMD may also have restless legs syndrome. A child with PLMD isn’t aware he’s kicking; RLS, however, involves an uncomfortable sensation in the legs, often described as a tingling, or the need to move.

Children with RLS will resist going to bed at night because lying down brings on the distressing sensations at their worst.

Both RLS and PLMD seem more common in children with attention deficit hyperactivity disorder. Some scientists think that similar brain chemicals may be involved in the conditions.

Sleep disorders often lead to irritability and other behavioral problems at school, with related trouble in concentrating and remembering. But these problems often clear up when sleep quality improves.

PLMD’s cause is unclear, but the condition appears to run in families. It may be associated with iron and folate deficiencies. Sometimes, if the deficiencies are treated, the condition abates. PLMD is also more common in children with leukemia, but most children with the disorder do not have leukemia.

Usually, however, PLMD persists. Medication may effectively treat it. Avoid caffeine, present in many soft drinks, and be sure that the child devotes an adequate amount of time to sleep. Some doctors think that moderate exercise a few hours before bedtime may help.

For more information, see “Take Charge of Your Child’s Sleep” by Dr. Judith Owens and Dr. Jodi Mindell, published by Marlowe & Co. 

Questions or comments should be addressed to Dr. T. Berry Brazelton and Dr. Joshua Sparrow, care of The New York Times Syndicate, 620 Eighth Ave., Fifth Floor, New York, N.Y. 10018. Questions may also be sent by e-mail to:

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