It’s a fight all parents are familiar with: the nightly battle to get their children to bed. Kids will try almost any tactic to avoid being tucked in for the night, and even then have long found ways to delay sleep with under-the-cover flashlights. But the deficit of sleep for today’s children and the degree to which that could be harming their short-term and long-term health was underscored last week by a new paper from University of Chicago and University of Louisville researchers. Led by David Gozal, professor and chair of pediatrics, and Karen Spruyt, assistant professor of pediatrics, the study used wristwatch-like activity monitors to objectively measure the sleep of more than 300 children between the ages of 4 and 10 for a week. Their results found that children are sleeping nowhere near the recommended amount of time, and that reduced or irregular sleep increases the risk of childhood obesity.
Like other studies dealing with sleep and weight gain, the research received a flood of media coverage, from sources such as CNN, the New York Times, and Time Magazine. ScienceLife conducted an extended interview with Dr. Gozal to dig deeper into the issues raised by the study, including how sleep deprivation is like an overdrawn bank account, how poor childhood sleep can predispose a child to a lifetime of health problems, and what parents can do to make sure their child is getting adequate rest at night. Here is an edited transcript of that conversation.
Q: What differentiates this study from previous studies of childhood sleep and obesity?
Gozal: Other investigators have conducted studies assessing sleep objectively using an actigraph, but the usual duration of those studies was either one day or three days. There was a study out of China where they actually identified for the first time that kids who slept more during the weekend were somewhat protected from the risk of obesity. Our study set out to look at a US population, to look objectively at both the week and the weekend, and to look at blood correlates of risk. This has never been done, to really look at what impact relatively short sleep or irregular sleep would have on the risk of disease later in life.
Q: What links did the study find between this lack of sleep and obesity?
We found that kids that slept the normally recommended number of hours were actually at the least risk. The kids that slept the least and had irregular sleep schedules were not only at very high risk, over fourfold, of obesity, but also showed a similar increase in metabolic and cardiovascular risk factors. When they tried to compensate during the weekends, the risk was less, but not eliminated. These kids were still at almost a threefold increased risk in obesity, but it’s better than a fourfold increased risk.
Q: The study revealed that he kids (aged 4-10) slept on average about 8 hours a night. Was this a surprise? Is it a concern?
It was a suspected surprise, because in the process of verifying the validity of actigraph recordings in children, we already became fully appraised of the misclassification that parents will assign to the duration of their own children’s sleep. On average, parents tend to overestimate the duration of sleep that their kids get by between 60 and 90 minutes. The moment parents close the door on their children, when they’re a certain age and above, they really don’t know what’s happening. They assume that 15-30 minutes later their kids will be asleep, when in fact it’s not true at all. I remember as a kid myself telling good night to my mom and then taking a little flashlight and book and reading for a long time. Now I’m sure what kids do is pull out their gadgets: phones, computers, mini-TVs, and video games.
The other thing that actually is rather remarkable is that over 80 percent of our kids in our country don’t wake up by themselves, they actually need to be awoken by their parents, which indicates that they still need more sleep, but aren’t getting it. There’s a paper from 1913 which measured and observed that kids of this age would sleep, on average, 10 hours. So the recommendations of all the organizations that are involved in sleep coincide on the need in this age group being 9-1/2 to 10 hours.
I’ve always said you need to look at this as if you were running a bank account. Call it a sleep account. If kids on average have an overdraft every night of two hours of sleep, by the end of the week, after five days of school, they will owe themselves and owe the account about 10 hours. If they continue doing the same during the weekend because they have friends, they want to do all these activities, and sleep is not perceived by the family as important, then they will further owe themselves an additional 4 hours, which gives an overdraft of 14 hours.
Q: So is “catch-up” sleep on the weekend an advisable way to recover from a sleep deficit?
Even if kids are catching up on sleep during the weekend, and let’s say they over-sleep two hours, then they would only reduce the debt of 10 hours accumulated during the week to about 6 hours. In both cases, they’re on overdraft, and long-term their credit history is gone. Also, you must remember, like a real bank account you’re going to pay a penalty every time you are going into overdraft.
It is possible to catch up but it often takes much longer than a weekend. If you take a mouse and you deprive them of a single night of sleep, their recovery takes about 3-5 days. Humans are about the same. If you’re a doctor and you’re on call overnight, the day post-call is actually terrible. The night after you are on call you sleep a little bit more, because obviously you come home and go right to sleep. But the day after that night, you still feel terrible. For 2-3 days, you’re still tired.
Q: How could insufficient or irregular sleep cause obesity?
There are many factors for obesity, so to take sleep alone as the only culprit is narrow minded, and we can’t do that. Sleep is not the driver for obesity, it is a driver. You have genetics, psychosocial settings, feeding patterns, habit, access to specific types of food, physical activity, and of course sleep.
We know from the work of Eve Van Cauter that people who sleep less have higher levels of ghrelin [a hormone related to hunger], and that their feeding patterns are clearly towards more junk food than healthy food. In mice, we know that if you restrict sleep or disrupt sleep you are going to have increased appetite and excessive food intake. Second, reduced sleep or altered sleep alone without any other disease will change your metabolism to an energy-saving mode, which makes you essentially less able to lose a calorie. Third, you have reduced physical activity, because if you’re tired you’re not going to engage in vitally important exercise. Fourth, there have been wonderful papers in recent years showing that the circadian clock is a metabolic regulator. If you are misaligned in relation to your circadian clock because of irregular sleep patterns, you may induce a pattern that is again conservation of energy, which in turn results in weight accretion.
Q: What did measuring the risk factors for obesity and other health problems tell you?
If you sleep less or you sleep more irregularly, you are creating a disruption of the normal homeostasis of your body, particularly as it relates to inducing an inflammatory state. We know that obesity is a systemic inflammatory disease and I am sure there are little things that get started and amplified the longer you go with inappropriate amounts of sleep. That’s how we look at this – it’s not a disease now. These kids are not going to have diabetes, or not going to have a myocardial infarction, as young children. But if you keep doing this for 25 years, then you’ll have your fatal heart attack at age 30 when you’ve become very obese and you’ve been mistreating your body and vessels for all this time.
Q: Why do you think kids are not getting adequate sleep in today’s world?
Families don’t have a good bedtime routine. Parents tend to work later, they come home later, they have dinner later; everything gets pushed back. Their last priority at the end of all this is that sleep needs to happen. It is very likely that in the context of real life, the most important sacrificial lamb is actually bedtime, and that’s the one that shows.
When parents have very good established, regular, predictable bedtime routines, kids learn it. They adjust, they align their circadian clock to the routine, and by aligning then they will be sleepy at the right time, because they’re used to it. However, if you go to sleep one night at 11, the next night you go to bed at 7, the next night 9, then you’re confused, and your body is confused. Even if you are trying to sleep one night at 7 to catch up, you’re not aligned with the clock and it’s difficult to fall asleep.
Now, I have the easy task, I just have to tell them, the parents, what to do. As a parent you need then to implement that routine, and it’s very difficult in the modern life where both parents work.
Q: So what do you recommend parents do to make sure their children are getting appropriate amounts of sleep?
First of all, parents can’t think that just by putting kids to bed that sleep is going to happen. We recommend to take away all the electronics from the room. Identify a contract with the kid: this is when you need to go to sleep, this is when you need to wake up to go to school. Let’s first of all make a regular bedtime, and we’ll give you the opportunity to engage for 30 minutes in some kind of soothing activity that is predictable: read, tell a story, talk about your plans for the next day, or what you did today. And then lights off, and you try to sleep. You assume that all that will take about an hour. This approach will not only have beneficial effects on children’s health, but also enable more communication between parents and children.
In general, what we find is that kids who essentially go back to a well established and predictable routine where their sleep is preserved are happier, learn better, have much more ability to pay attention in school, are more inclined to exercise and engage in physical activities, and of course they have reduced appetite and all these other things we have talked about that promote obesity and long-term risks. It’s a win-win for everybody.
Spruyt K, Molfese DL, & Gozal D (2011). Sleep Duration, Sleep Regularity, Body Weight, and Metabolic Homeostasis in School-aged Children. Pediatrics PMID: 21262888