Short Nighttime Sleep in Early Life Linked to Subsequent Obesity

Laurie Barclay, MD

September 7, 2010 — Short nighttime sleep duration in early life is linked to obesity later in life, according to the results of a prospective cohort study reported in the September issue of the Archives of Pediatric & Adolescent Medicine.

"Short sleep duration may increase the risk of obesity in children and adolescents," write Janice F. Bell, PhD, MPH, from the University of Washington in Seattle, and Frederick J. Zimmerman, PhD, from the University of California, Los Angeles. "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. In several studies, a strong dose-response relationship is evident with increasing odds of overweight/obesity associated with fewer hours spent sleeping."

Using the US Panel Survey of Income Dynamics Child Development Supplements (PSID-CDS) in 1997 and 2002, the investigators aimed to evaluate associations between daytime and nighttime sleep duration and subsequent obesity in 1930 children and adolescents, aged 0 to 13 years at baseline in 1997.

Short daytime and nighttime sleep durations at baseline were defined as less than the 25th percentile of age-normalized sleep scores. At follow-up in 2002, body mass index (BMI) was converted to age-specific and sex-specific z scores and characterized as normal weight, overweight, or obese with use of established cutoff points. The relationship between BMI classification and short daytime and nighttime sleep at baseline and follow-up was assessed with ordered logistic regression. Important covariates including socioeconomic status, parents' BMI, and BMI at baseline for children older than 4 years were also used.

Among children aged 0 to 4 years at baseline, short duration of nighttime sleep at baseline was strongly associated with a higher risk for subsequent overweight or obesity (odds ratio, 1.80; 95% confidence interval, 1.16 - 2.80). Among children aged 5 to 13 years, however, baseline sleep was not associated with subsequent weight status, but contemporaneous sleep was inversely associated. In both groups, daytime sleep was not significantly associated with subsequent obesity.

"In the older cohort, nighttime sleep at follow-up was associated with marginally increased odds of obesity at follow-up, while sleep duration 5 years prior had no significant effect," the study authors write. "These findings suggest that there is a critical window prior to age 5 years when nighttime sleep may be important for subsequent obesity status."

Limitations of this study include collection of sleep data for only 2 days in a year, lack of baseline BMI data for the younger children, potential confounding by physical activity and diet, and reliance on parental report for baseline weight.

"Shortened sleep duration in early life is a modifiable risk factor with important implications for obesity prevention and treatment," the study authors conclude. "Insufficient nighttime sleep among infants and preschool-aged children may be a lasting risk factor for subsequent obesity. Napping does not appear to be a substitute for nighttime sleep in terms of obesity prevention."

The Health Resources and Services Administration/Maternal and Child Health Bureau supported this study. The study authors have disclosed no relevant financial relationships.

Arch Pediatr Adolesc Med. 2010;164:840-845.