A recent study out of New Zealand suggests that educating parents about sleep prior to the birth of their child, and supporting sleep training during early childhood, can reduce the risk of obesity in childhood. This adds to the literature relating sleep and childhood obesity. Although this is music to my ears, do these results make sense? Let’s dig into it.
My friend Sumathi Reddy sent me a link to a Medscape article entitled, “Amazing’ Reduction in Obesity at Age 5 From Early Sleep Training”. As always, the journal article has a less sexy title: “Sleep, nutrition, and physical activity interventions to prevent obesity in infancy: follow-up of the Prevention of Overweight in Infancy (POI) randomized controlled trial at ages 3.5 and 5 y” (sadly behind a paywall)1.
This was a large trial which enrolled 802 women in New Zealand who were pregnant with the goal of examining two educational and support programs to see if they would reduce the risk of obesity in children at age five. There were two interventions in the trial which are described in an earlier publication:2
- An intervention teaching the mothers about food, activity, and breastfeeding (FAB). Parents in this group received eight extra education and support visits over the first 18 months of life, starting with education prior to birth and including lactation support and physical activity sessions, as well as education about the importance of limiting screen time and maximizing exercise in early childhood.
- An intervention focused on developing good sleep habits from birth on. This is comprised of a group session prior to birth, and home visits at three weeks, four months, and six months of age. Anytime between six months and three years of age, the parents could request more intensive sleep health from the research team which included developing a behavioral plan (e.g. sleep training plan) for the family.
When the children in the study were 3.5 years of age, there was no difference in sleep duration or timing, but there was a decrease in resistance to bedtime.
Here’s where it gets interesting. The researchers found that the children in the Sleep intervention group were significantly less likely to be obese at age 5 when compared with the FAB group or the controls (the children who did not receive any intervention), even though there was no difference in sleep duration at age 3.5. This was a major result, with the risk of obesity halved in the children who had received the sleep intervention, compared with other groups. Even more interesting, the children in the FAB intervention were morelikely to be obese than the control children.
What does sleep have to do with obesity in children?
There is a growing body of evidence which suggests that insufficient sleep at night is associated with increased appetite and weight gain in both children and adults. The reasons for this are not entirely clear, but studies of volunteers who are sleep deprived showed lower levels of leptin (a hormone which make you feel less hungry) and higher levels of ghrelin (a hormone associated with increased appetite, often for sugary or fatty foods). Here’s a video I did a few years ago on this topic:
How believable are these results?
This study has some significant strengths. It was a large study that followed children from before birth— such studies that go forward in time (called prospective studies) are generally considered superior to studies that look back in time (called retrospective studies).
Some children and family dropped out of the study, which is fairly typical— about 30% in this case. The authors did some complicated statistical work to show that the children that dropped out are unlikely to affect the results. But it would be better if more the children were followed until the end of the study.
The main issue I have with the study is that I would like to know more about the results of the sleep intervention. (I am, after all, a sleep doctor). A prior article written about this study showed that there was no apparent difference in sleep quality based on parent observation3. However, actigraphy (measurements by a small device which tracks sleep and wake in the home) showed that there was an 8% reduction in the frequency of night time awakenings and an average of 6 minutes more sleep at night. These numbers were statistically significant (meaning that the data in the study suggested that these findings were not random) but probably did not make a huge difference to the parents.
What do these results mean?
Although the media tends to trumpet striking findings such as these, it’s important to recognize the limitations of this study. New Zealand (where this study was performed) is a long way from where I live in the United States, and has a much more robust social safety net. Thus the FAB intervention could be useful here although it was not for the families in this study. As to why the children in this group were more likely to be obese, I don’t feel qualified to venture a guess.
One thing I don’t understand is why the children in the Sleep intervention were less likely to be obese. Study results at 6 months and two years of age did not demonstrate any clinically significant difference in sleep between the Sleep group and the other groups, although there was a small difference in sleep duration and nocturnal awakenings at 6 months of age . If I would hazard a guess, this suggests to me that even small improvements in sleep quality or duration may help “program” a child’s metabolism towards a healthier weight, although that is at best supposition.
What’s the take home of this study?
For unclear reasons, children whose parents had intensive education and support around sleep prior to and after birth were less likely to be obese at five years of age. It’s not clear why as they did not sleep appreciably more than the other children in the study. However, this adds to the growing body of evidence that healthy sleep in early childhood is one factor which determines healthy weight. Also, that sleep interventions such as sleep training may have benefits as children get older outside of the proven benefits of improved sleep for children and parents.
What do you think? Please leave your comments below and, as always, share this article with your friends if you find it interesting.
- Taylor, R. W. et al. Sleep, nutrition, and physical activity interventions to prevent obesity in infancy: follow-up of the Prevention of Overweight in Infancy (POI) randomized controlled trial at ages 3.5 and 5 y. The American Journal of Clinical Nutrition 108, 228–236 (2018). ↩︎
- Taylor, B. J. et al. Prevention of Overweight in Infancy (POI.nz) study: a randomised controlled trial of sleep, food and activity interventions for preventing overweight from birth. BMC Public Health 11, (2011). ↩︎
- 1.Galland, B. C. et al. Anticipatory guidance to prevent infant sleep problems within a randomised controlled trial: infant, maternal and partner outcomes at 6 months of age. BMJ Open 7, e014908 (2017). ↩︎