Split and continuous sleep in teens impact cognition and glucose levels differently

February 22, 2019

Science Daily/Duke-NUS Medical School

Under conditions of insufficient sleep, effects on cognitive performance and morning glucose levels vary depending on how sleep is distributed.

Many adolescent students sleep less than the recommended duration of 8-10 hours a night. It is unclear; however, whether short night sleep combined with an afternoon nap is as good as having the same amount of sleep continuously during the night without a nap. Researchers at Duke-NUS Medical School have demonstrated for the first time that different sleep schedules with the same total sleep opportunity over 24 hours may have dissimilar effects on cognition and glucose levels. This is the first study to gather experimental evidence on the notion that 'what may be appropriate sleep for one health goal may not be for another'.

The handful of studies that examined split sleep schedules with normal total sleep duration in working-age adults found that both schedules yield comparable brain performance. However, no study has looked at the impact of such schedules on brain function and glucose levels together, especially when total sleep is shorter than optimal. The latter is important because of links between short sleep and risk for diabetes.

The researchers measured cognitive performance and glucose levels following a standardized load in students, aged 15-19 years, during two simulated school weeks with short sleep on school days and recovery sleep on weekends. On school days, these students received either continuous sleep of 6.5 hours at night or split sleep (night sleep of 5 hours plus a 1.5-hour afternoon nap).

"We undertook this study after students who were advised on good sleep habits asked if they could split up their sleep across the day and night, instead of having a main sleep period at night," said Prof. Michael Chee, Director of the Centre for Cognitive Neuroscience, Professor of Neuroscience and Behavioral Disorders Programme, Duke-NUS Medical School and one of the study's senior authors. "We found that compared to being able to sleep 9 hours a night, having only 6.5 hours to sleep in 24 hours degrades performance and mood. 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. This finding is remarkable as the measured total sleep duration over 24 hours was actually less in the former group," Prof. Chee added.

However, for glucose tolerance, the continuous schedule appeared to be better. "While 6.5 hours of night sleep did not affect glucose levels, the split sleep group demonstrated a greater increase in blood glucose levels to the standardized glucose load in both simulated school weeks," noted Dr. Joshua Gooley, Associate Professor of Neuroscience and Behavioral Disorders Programme, Principal Investigator at the Centre for Cognitive Neuroscience, Duke-NUS Medical School and the senior co-author of this study.

Although further studies are necessary to see if this finding translates to a higher risk of diabetes later in life, the current findings indicate that beyond sleep duration, different sleep schedules can affect different facets of health and function in directions that are not immediately clear.

Professor Patrick Casey, Senior Vice Dean of Research, Duke-NUS Medical School, commented, "Recent sleep surveys show that Singaporeans are among the world's most sleep deprived people. This is the latest in a series of studies from a team of researchers from the Neuroscience and Behavioural Disorders Programme and Centre for Cognitive Neuroscience that have provided valuable insights into the importance of good sleep."

https://www.sciencedaily.com/releases/2019/02/190222101312.htm

Older People Advised That Taking an Afternoon Nap Can Lead to More Active Lives

October 26, 2010

Science Daily/University of Surrey

Experts at the University of Surrey discovered that many older people felt that they may be branded lazy for taking afternoon naps so they tried hard to avoid nodding off.

But the occasional nap can make older people more able to lead a fully active life by giving them enough energy to take part in recreational and social activities.

Susan Venn, of the Department of Sociology said: "Sleep is central to health and well-being, but as people get older, the quality of their sleep can deteriorate. They shouldn't feel guilty or think themselves lazy for having a nap."

The new research also found that as older people often have more disturbed sleep patterns at night they try to avoid taking a nap during the day only to fall asleep watching television during the early evening. As a result they may end up feeling exhausted..

Another finding was that older men and women lose sleep because of having to get up several times a night to go to the toilet, so they may cut down on drinking fluids during the day believing this will help, even though they may become dehydrated.

One interviewee, called Anne, aged 71, from Berkshire, said "My main sleep problem is waking up in the early hours of the morning and not being able to get back to sleep.

"I sometimes find on a particularly bad night that I'm awake for three or four hours. I don't want to disturb my husband by tossing and turning, and trying to get back to sleep, so I tend to get up and do the housework, watch DVDs or use the computer.

"Sleep at the moment is a disappointment I suppose, because I feel I've improved my life style by doing all the things, diet, exercise and all this, and I'd hoped that the sleep would improve more than it has."

Susan Venn, of the Department of Sociology, a researcher on the project, explained: "Many of the older people we talked to described how disturbed their sleep was, especially in terms of waking up a lot in the night.

"Anne was like many of the older people we spoke to in that being active during the day was very important to them, and if they slept badly, it impacted on how much could be achieved.

"Many older people are prescribed medications to help them sleep, but research has shown that sleeping medication may impact on the lives of older people, such as increasing the risk of falls."

The new research called "Understanding poor sleep in the community" is linked to an academic conference on sleep issues among older people, based on the SomnIA (Sleep in Ageing) project (www.somnia.surrey.ac.uk).

The research by academics at the University of Surrey, along with colleagues at other institutions, tried to find ways of improving the sleep patterns of older people.

Researchers talked to 62 older men and women who are living in their own homes about their poor sleep patterns and three key findings emerged:

• Whilst many older people do not sleep well and feel tired during the day, they often do not want to take a nap because they believe daytime sleeping is a sign of laziness.
• Older people often get up in the night to go to the toilet, sometimes even several times a night. So, counter to current advice to drink plenty of fluids during the day, they may often severely restrict how much they drink.

• Older men and women would rather not visit their doctor for problems with their sleep, largely because of a concern they will be prescribed some form of sleeping medication. Keeping busy and active is important to many older people and they are concerned that sleeping medication may take away that control. Women, more than men, tended to explore alternative treatments and remedies for poor sleep, such as over the counter remedies and herbal medicines.

http://www.sciencedaily.com/releases/2010/10/101026090834.htm