14 DAY TRIAL // Insufficient nighttime sleep among infants and young children can be associated with a risk of obesity later in life, suggests a new study published in the September issue of Archives of Pediatrics & Adolescent Medicine, adding that napping does not compensate.
Janice F. Bell, PhD, MPH, of the University of Washington, Seattle and Frederick J. Zimmerman, PhD, of the University of California, Los Angeles, gathered all existing national data on children and teenagers and carried out a survey on 1,930 children ages 0 to 13 years.
The children were separated into two groups, one from 0 to 59 months and the other from 60 to 154 months of age, and all information was collected in two steps, once in 1997 and then in 2002, as follow-up.
What the study's authors found at follow-up was that “33 percent of the younger cohort and 36 percent of the older cohort were overweight or obese.”
In the younger group, short nighttime sleep was the cause of overweight or obesity, as for the older group, there was no significant evidence that baseline sleep was linked to consequent weight status, but contemporaneous sleep was associated with high risk of passing from normal weight to overweight and from overweight to obese at follow-up.
Also, in the older group, nighttime sleep at follow-up was related to slightly increased odds of obesity at follow-up, while five years later sleep duration had absolutely no effect.
This is why the authors concluded that “there is a critical window prior to age 5 years when nighttime sleep may be important for subsequent obesity status.”
The researchers write that “obesity – defined as having age- and sex-specific body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) at or above the 95th percentile of national growth standards – has doubled among children aged 2 to 5 years and adolescents aged 12 to 19 years and has tripled among those aged 6 to 11 years” during the last three decades.
“Evidence is accumulating from cross-sectional population studies to support a robust contemporaneous relationship between shortened sleep duration and unhealthy weight status in children and adolescents.”
As a conclusion they say that “sleep duration is a modifiable risk factor with potentially important implications for obesity prevention and treatment.”
They add that “insufficient nighttime sleep among infants and preschool-aged children appears to be a lasting risk factor for subsequent obesity, while contemporaneous sleep appears to be important to weight status in adolescents,” [as for] napping, it “had no effects on the development of obesity and is not a substitute for sufficient nighttime sleep.”