Infants who sleep longer through the night and with fewer interruptions may be less likely to become overweight during their first six months of life, according to a study published in the journal SLEEP. While the research only showed a link - not a cause-effect relationship - between infants' sleep and weight, the findings suggest that newborns can reap some of the same health benefits that others get from consistent, quality shut-eye.
The research emerged from the Rise and SHINE (Sleep Health in Infancy & Early Childhood) study, which analyzes ways sleep may influence a newborn's growth and development. The five-year study is being supported in part by the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health.
"What is particularly interesting about this research is that the sleep-obesity association we see across the lifespan appears in infancy and may be predictive of future health outcomes," said Marishka K. Brown, Ph.D., director of the National Center on Sleep Disorders Research, located within the NHLBI. Brown noted that multiple studies have shown links between good sleep and improved health. For children, this includes a reduced risk of developing obesity and diabetes, while supporting development, learning, and behavior.
In the current study, researchers observed 298 newborns and found that for every hourly increase in nighttime sleep, measured between 7 p.m. and 8 a.m., the infants were 26% less likely to become overweight. Likewise, for each reduction in nighttime awakening, they were 16% less likely to become overweight.
To conduct the study, researchers partnered with mothers who delivered a baby at Massachusetts General Hospital between 2016-2018. Unlike other infant sleep studies, which have relied on parent reports, the researchers used ankle actigraphy watches to objectively track nighttime movement, capturing three nights of data at the first- and six-month marks.
Parents also kept infant sleep diaries and shared insights about activities that could have impacted each infant's sleep pattern or weight, like how often they breastfed or whether the infant had eaten solid food before age four months.
To assess weight, the researchers used the World Health Organization's age and sex-specific growth charts. An infant was considered overweight if they were at or above the 95th percentile for weight and length. The researchers also took maternal health and sociodemographic considerations into account while reviewing the data.
Susan Redline, M.D., M.P.H., a study author who is also a senior physician at Brigham and Women's Hospital and a professor of sleep medicine at Harvard Medical School, said her colleagues were intrigued with the idea of studying associations between infant sleep patterns and weight. Mainly, they wanted to understand what happened as infants progressed from the sporadic sleep schedules common in early infancy to a longer overnight sleep pattern. They found infants who progressed to steady nighttime sleep - 8.8 hours a night on average by the end of the study - and who had fewer nighttime awakenings were less likely to be overweight in those first six months.
After the first month, researchers found 30 of the infants (10.3% of the study sample) were overweight, although most - 21 - reached a normal weight at six months. At the end of the six-month mark, 26 infants (8.8%) were overweight, including 15 who were not previously overweight.
The researchers suspect a few factors could explain these results. Some parents may soothe infants who have trouble sleeping by providing milk or introducing them to solid foods. Also, if an infant was not getting enough high-quality sleep at night, they could have felt hungry and tired the next day - leading to more eating and less movement, which in turn could contribute to the infant's weight. While additional data is needed to observe these potential links and any other impacting factors, the evidence so far suggests that sufficient and consolidated sleep could be powerful tools in reducing obesity risks early in life.
This study underscores the importance of sleep health not just for adults, but for people of all ages. Parents should consult with their pediatricians on the best practices to promote healthy sleep, which can include keeping consistent sleep schedules, providing a dark and quiet space for sleeping, and finding the most appropriate ways to respond to infant awakenings."
Susan Redline, Study Author
Li, X., et al. (2021) Longitudinal association of actigraphy-assessed sleep with physical growth in the first 6 months of life. Sleep. doi.org/10.1093/sleep/zsab243.