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THE QUESTION Taking a nap has long been part of the daily routine for most small children. How might napping affect their health and development?

THIS STUDY analyzed data from 26 studies that examined the effects of napping on 8,168 children up to 5 years old. Among children older than 2, napping was linked to delayed and disrupted sleep. Those children took longer to fall asleep, slept for a shorter time and had a poorer quality of sleep than children who did not nap.

Whether napping affected the children’s health and behavior was less clear. Some studies found such things as increased anxiety, more trouble adjusting to preschool, and a greater tendency to withdraw and not be social among children who napped, compared with those who did not. But other studies reported positive effects on learning and memory for those who regularly took naps.

WHO MAY BE AFFECTED? Preschool-age children. Generally, children at that age need 11 to 12 hours of sleep a day. From birth till about 5, children’s sleep patterns shift, with increasingly more sleep at night and less during the day.

CAVEATS None of the analyzed studies were randomized; most of the data came from parents’ assessments of children’s sleep.

FIND THIS STUDY Feb. 17 online issue of Archives of Disease in Childhood (www.adc.bmj.com; click on “Online First”).

LEARN MORE ABOUT naps for children at www.kidshealth.org (enter parents’ site). Learn about children’s sleep at www.sleepfoundation.org.

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.