Sleep study finds pros and cons to afternoon nap for teenage brain health


A fascinating study from a team of researchers in Singapore has revealed that a short night sleep with an afternoon nap is better for a teenage school student’s mood, memory and cognition than a longer, continuous night’s sleep. It wasn’t all good news though, as the researchers discovered these so-called split sleep students reported higher glucose levels, a marker that points to increased diabetes risk.

Teenagers need more sleep than healthy adults. Not only is it recommended that teenagers aim for between eight and ten hours of sleep per day, but puberty has been found to disrupt an adolescent’s circadian cycle, keeping them up at night and pushing them to sleep later in the morning. Add in early school start times and the result is a virtual epidemic of teen sleep deprivation, with one study finding as little as 15 percent of teenagers get the recommended amount of sleep.

Carried out at Duke-NUS (National University of Singapore), the new study set out to investigate whether there were marked differences in neurobehavioral function and metabolic markers between teenagers sleeping a single continuous stretch overnight, and those supplementing a shorter overnight sleep with an afternoon nap. The continuous sleeping group were limited to 6.5 hours per night, just under the general seven hour average reported by most teenagers. The split sleep group, on the other hand, were limited to five hours of sleep overnight, with a 90-minute afternoon nap.

Compared to a control group of teenagers sleeping the recommended nine hours a night, both sleep deprived groups displayed decreases in mood and cognitive performance. Unexpectedly, however, the split sleep group did demonstrate better performance on the cognitive tests than the continuous sleeping group.

“Interestingly, under conditions of sleep restriction, students in the split sleep group exhibited better alertness, vigilance, working memory and mood than their counterparts who slept 6.5 hours continuously,” says Michael Chee, one of the senior authors on the new study. “This finding is remarkable as the measured total sleep duration over 24 hours was actually less in the former group.”

The study also examined the effect of restricted sleep on blood glucose concentrations. Here, the results switched, revealing while the continuous sleep group showed little change in blood glucose levels, even compared to the nine-hour sleeping control, the split sleepers displayed significantly higher levels.

The researchers note it is unclear what the long term implications are for such higher glucose levels. There is a potential for adolescents at risk of diabetes to be more likely to develop the disease if these levels recurred for chronic periods of time, however further study is necessary to track rates of diabetes later in life and clearly establish a negative impact.

Unfortunately those looking for a clear answer over which is better – a continuous sleep or a split sleep – will be left with the frustrating conclusion that neither is ideal. Ultimately the researchers suggest both limited sleep schedules are not as beneficial as the recommended nine hours sleep per night.

The new study was published in the journal Sleep.

Source: Duke-NUS Medical School