children sleep deprived

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

Blue Light Could Help Teenagers Combat Stress

October 22, 2012

Science Daily/Rensselaer Polytechnic Institute (RPI)

A new study shows that exposure to morning short-wavelength “blue” light has the potential to help sleep-deprived adolescents prepare for the challenges of the day and deal with stress, more so than dim light.

 

Adolescents can be chronically sleep deprived because of their inability to fall asleep early in combination with fixed wakeup times on school days. According to the CDC, almost 70 percent of school children get insufficient sleep -- less than 8 hours on school nights. This type of restricted sleep schedule has been linked with depression, behavior problems, poor performance at school, drug use, and automobile accidents.

 

A new study from the Lighting Research Center (LRC) at Rensselaer Polytechnic Institute shows that exposure to morning short-wavelength "blue" light has the potential to help sleep-deprived adolescents prepare for the challenges of the day and deal with stress, more so than dim light.

 

Levels of cortisol, a hormone produced by the adrenal gland, follow a daily 24-hour rhythm. Cortisol concentrations are low throughout the day reaching a broad minimum in the evening before rising slowly again throughout the night. In addition to this gradual elevation of cortisol at night, cortisol levels rise sharply within the first 30 to 60 minutes after waking.

 

This is known as the cortisol awakening response (CAR). In nocturnal animals, the cortisol spike occurs at night, at the start of activity. It appears to be associated with the time of transition from rest to activity, upon waking. A high CAR has been associated with better preparedness for stressful and challenging activities.

 

"The present results are the first to show that low levels of short-wavelength light enhance CAR in adolescents who were restricted from sleep," said Figueiro. "Morning light exposure may help to wake up the body when it is time to be active, thus preparing individuals for any environmental stress they might experience."

 

Short-wavelength light has been shown to maximally suppress production of nocturnal melatonin and phase shift the timing of the biological clock. The effect of short-wavelength light on other biomarkers has not been widely studied.

 

The study included three overnight sessions, at least one week apart. All participants wore a Dimesimeter on a wrist band to measure light exposure and to verify the regularity of their activity/rest periods during the three-week study. The Dimesimeter is a small calibrated light meter device developed by the LRC that continuously records circadian light and activity levels.

 

During the study, adolescents aged 12 to 17 years went to sleep at 1:30 a.m. and woke up at 6:00 a.m., a 4.5-hour sleep opportunity. Each week, participants either experienced morning short-wavelength blue light (40 lux of 470-nanometer light) or remained in dim light.

http://www.sciencedaily.com/releases/2012/10/121022112847.htm

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