"Insufficient sleep degrades performance, focus and concentration, " says Kathy Gromer, the campus director for the Minnesota Sleep Institute in Burnsville, Minn.

WSJ: When It's Worth It to Skip a Workout and Sleep

These findings may explain the link between insufficient sleep and overweight that has been shown in previous studies, says the lead researcher, Marie-Pierre St.

CNN: Sleep deprivation spurs hunger

The most common sleep problems in children are difficulty falling asleep and staying asleep and overall insufficient shut-eye.

WSJ: More Children With Sleep Problems Seek Overnight Tests