WebMD News Archive
Can an early bedtime help children stay slim?
’Early to bed and early to rise’ - this may not make us healthy, wealthy, and wise as promised, but it might help children be leaner and more active, say researchers.
BMJ Group News
What do we know already?
Roughly 1 in 7 children in the UK are obese, and their numbers are rising, making this a pressing health concern for parents, doctors, and public health officials.
Many factors can influence a child’s risk of being overweight, including what they eat, how much TV they watch, and how much exercise they take. Studies also suggest their sleep habits might play a role, showing that children and adolescents who sleep fewer hours have a higher risk of being obese.
However, more recent studies have cast doubt on this connection, finding a weaker link between sleep duration and weight than previously suggested.
In the new study, researchers wondered whether earlier trials might have missed the mark by focusing on how long children sleep rather than the timing of their sleep. In theory, children who go to bed earlier and wake earlier would have more daylight hours for being physically active, while night owls would have more of their waking time after dark, leaving less time for active pursuits.
To test this theory, researchers recorded the bedtimes and rising times of 2,220 Australian children, aged 9 to 16 years, and compared their weight and their use of free time over four days. The children also wore a device for several days that recorded how many steps they took (a pedometer).
What does the new study say?
Children who went to bed late and got up late were 1.5 times more likely to be obese than those who went to bed early and got up early, despite getting the same amount of sleep (around 9 hours and 40 minutes).
Night owls were also nearly three times more likely to sit in front of a TV, computer, or video game for two or more hours a day. They averaged 48 minutes longer in front of a screen daily than their early-bird peers, primarily between 7 p.m. and midnight.
On average, the early group went to bed at 9:20 p.m. and rose at 7:03 a.m. The late group retired at 10:46 p.m. and rose at 8:22 a.m.
How reliable is the research?
This study provides a plausible link between children’s bedtimes and their weight, showing that early sleepers and risers - who have more daylight waking hours - are indeed more active and less likely to be obese.
However, we still can’t be certain that the participants’ sleep schedules are what led to the differences in their physical activity and weight. Many things can influence these factors. The researchers accounted for some of these, including the children’s ages, average hours of sleep, where they lived (urban, regional, or more remote areas), and household income. But they didn’t look at other things that might have played an important role, such as the children’s diets and whether they had any health problems, such as asthma, that might have limited their activity.
Also, it’s worth noting that the researchers assessed the children’s bedtimes and daily activities by having them answer questionnaires. This isn’t the most reliable way to gather information, although the researchers did use pedometers to help confirm the children’s activity levels.