Land of nod critical for under 5s

Children under the age of 5 who don't get enough sleep at night are more likely than kids who do to become obese at a young age, a news study shows.
"We found a robust longitudinal association between duration of night-time sleep in early life and subsequent obesity measured at 5 to 9 years," wrote the authors of the study.
Researchers, led by Janice Bell of the University of Washington, Seattle, and Frederick Zimmerman of the University of California, Los Angeles, studied two lots of data - at baseline and five years later - for 1930 children in the United States.
The kids were separated into two groups: ages 0 to 59 months, and 5 to 13 years. The data analysed included information known to influence whether a child develops obesity, including parents' weight and the child's physical activity level, plus how long the children slept at night, including naps.
On average, younger children in the study slept 10 hours a night, and older children slept about 9.5 hours, but some children in both age cohorts got as little as five hours' sleep a night.
The data collected five years after baseline showed 33 per cent of the younger cohort and 36 per cent of the older cohort of kids were overweight or obese.
"For the younger children, low night-time sleep at baseline was significantly associated with increased odds of overweight versus normal weight and increased odds of obesity versus overweight at follow-up," the study says. It states almost one in five US children is obese and more than a third are overweight, and ensuring very young children get enough sleep at night could play a key role in preventing obesity.
Daytime napping appeared to have no effect on the children's weight, and getting little sleep at night also did not affect the weight of the older children.
"These findings suggest that there is a critical window prior to age 5 when night-time sleep may be important for subsequent obesity status."
Why sleep affects weight is not precisely known, but the authors said getting less sleep could lead to "decreased physical activity due to tiredness and increased energy intake" because the waking child has more chances to eat.
The study found that another possible reason why lack of sleep leads to weight gain is that the number of hours of shut-eye influences hormones that affect appetite, hunger and metabolism.