A study of 7-year-olds has found that sleeping less than nine hours a night was associated with being overweight or obese, even after accounting for amounts of television watching and physical exercise.
The study, being published Tuesday in the journal Sleep, also found that short sleep duration was associated with mood swings. The researchers had followed the subjects — 519 children in New Zealand — since birth, making periodic health and developmental assessments and interviewing their parents.
Sleep time did not affect I.Q. scores or measures of attention-deficit/hyperactivity disorder, but children who averaged less than nine hours’ sleep were significantly more likely than the others to be overweight.
The Parable of Parabola: What the U-Shaped Curve Can and Cannot Tell Us about Sleep