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Babies’ sleep tied to childhood obesity
When the wind blows, the cradle will rock. And when babies sleep less,
they may gain too much weight. A new Harvard study finds that babies and
toddlers who sleep fewer than 12 hours daily are at greater risk for
being overweight in preschool, startling evidence that the link between
sleep and obesity may affect even very young children.
TV viewing heightened the effect. The children who slept the least and
watched the most television had the greatest chance of becoming obese.
“The two (behaviors) are acting independently. In combination, they are
particularly risky,” said the study’s lead author, Dr. Elsie Taveras of
Harvard Medical School. The findings, published in April’s Archives of
Pediatrics & Adolescent Medicine, are based on mothers’ reports of their
babies’ sleep habits and TV viewing, and direct measures of the
children’s height, weight and skinfold thickness.
Starting when the babies were 6 months old, mothers were asked how long
their children napped during the day and how long they slept at night.
Moms were asked again when the children were 1 and 2 years old. They
were asked about TV time when the children reached age 2.
The researchers combined the sleep answers to find an average pattern
for each child during the first two years of life. They found 586 of the
children slept an average of 12 or more hours a day and 329 of the
children slept less than that. Among the long sleepers, 7 percent were
obese at age 3.
The short sleepers fared worse. Twelve percent of them became obese
3-year-olds. Adding TV to the picture, 17 percent of those who slept
less than 12 hours a day and watched two or more hours of television a
day were obese by the time they were 3. Obesity was defined as having a
body mass index in the 95th percentile or above. BMI is a measure that
combines height and weight. A 3-year-old who is 3 feet, 3 inches tall
and 40 pounds would be considered obese.
The researchers took into account other risk factors for obesity,
including TV viewing, and still found the children who slept fewer than
12 hours a day had a doubled risk of being obese at age 3 than the other
children. Sleep’s impact on appetite hormones may explain the effect,
Taveras said. In prior studies, sleep-deprived adults produced more
ghrelin, a hormone that promotes hunger, and less leptin, a hormone that
signals fullness.
TV viewing is thought to increase the risk of obesity both because it
takes time away from calorie-burning play and because of food ads for
snacks and fast food. The families in the new study lived in
Massachusetts and had relatively high incomes and education levels,
making it difficult to apply the findings to everyone, Taveras
acknowledged. Sleep researchers who read the study said it adds to
growing evidence of the link between poor sleep and obesity. A study
published last year found that every additional hour per night a
third-grader spends sleeping reduces the child’s chances of being obese
in sixth grade by 40 percent.
“The main message for parents is that there has to be regularity in
sleep in children. It’s very important to maintain a schedule,” said Dr.
Michelle Cao of Stanford University’s sleep disorders clinic. She wasn’t
involved in the study but co-wrote an accompanying editorial in the
journal. Taveras recommended practices that teach infants to fall asleep
on their own, putting them to bed when they’re drowsy but not fully
asleep. Pat Prinz of the University of Washington, who wasn’t involved
in the study, said parents who rely on day care should make sure their
toddlers have plenty of time to run, jump and play.
“The more active they are in the day, the better they’ll sleep at
night,” Prinz said. But she cautioned that genetics may play a role in
sleep and a person’s genetic makeup may limit how much sleep duration
can be improved.
—Online |
