Previously unknown sleep pattern revealed in new research

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(Medical Xpress)—There's no need to panic if you didn't get a solid eight hours of beauty sleep last night. According to new University of Sydney research, sleep duration naturally waxes and wanes over a period of days regardless of individual lifestyle, timing of sleep or waking, and social and environmental influences.

With further research, the discovery could have important implications for predicting , managing fatigue-related accidents after , and treatment recovery in clinical populations.

" requirements vary in a cyclical fashion and between individuals. If you incur a sleep debt, your body will signal a need to catch up on extra sleep," says Dr Chin Moi Chow, principal investigator of the article published in Nature and Science of Sleep.

"As you increase your to recover from the debt, your ability to prolong wakefulness increases. Then, as prior increases, sleepiness is inevitable, and a need for further sleep develops again."

Dr Chow and colleagues Shi Wong and Dr Mark Halaki, from the University's Faculty of Health Sciences, monitored a group of healthy young males over a fortnight using an - a small activity recording device worn like a wristwatch on the non-dominant arm - designed to measure sleep patterns.

To the researchers' fascination, the actigraph data showed participants' sleep duration oscillated in a sine wave pattern - a phenomenon that had not previously been observed. Clear periodic patterns were found in the majority of the participants, varying from periods of between two and 18 days.

The cyclic pattern observed in the research suggests that the sleep balance mechanism operates on an ongoing basis in daily life, with changes in sleep duration constantly accompanied by compensatory adjustments.

Interestingly, despite the fact that participants in the study habitually slept below the recommended seven to eight hours a night, they still maintained a cyclic sleep duration pattern.

"Our sleep quantity and quality vary according to a range of factors," Dr Chow says. "Some individuals have a slower accumulation or faster dissipation of sleep pressure, which may define their pattern of total sleep time."

Variations in daily sleep duration may also arise from differences such as slight variations in the body clock or external factors like temperature, daylight, exercise, or eating and drinking patterns.

"Changing your on weekends, or resetting the pattern through shift work, could alter your sleep duration cycle and could put the body under significant strain," says Dr Chow.

This research is part of Dr Chow's broader interest in the lifestyle factors influencing sleep. The team hopes to follow the research by examining the cyclical phenomenon in special groups such as long or short sleepers and people with insomnia.

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Jan 29, 2013
Rotaing shift work has been widely studied and show to compromise individuals' health. And yet it remains a feature of most health workers' employment patterns. Oh the irony - efficiency built on fiscal interests prioritised over workers' health. Doctors and Nurses must remind health organisations about the value in modelling good practice. I guess the compromise is considered from a corporate risk mindset; staff being just a cost-centre to magage tightly... when there are no short-term liabilities that can bite the corporate body. Mobidity from shift work can take years ti manifest, years enough that there is no legal redress available to that employee who left say five years ago and now lives with the stress-induced illness from their hopsital job.

Jan 29, 2013
Sleep fascinates me. Why do we sleep at all? The facile answer is that we sleep because we are tired.
However, evolution works on subtle advantages for procreating. And the act of sleeping is not a subtle indiscretion. It is extremely maladaptive.
As far as I know all the vertebrates do it. Evolutionary competition should have ruthlessly eliminated this phenomenon.
Why hasn't it? why can evolution not do a work-around. I understand the cetacea sleep one hemisphere at a time, so they have a work-around.
But the mystery is unresolved. Why do we have to sleep at all?
I'm off to bed.
Thats it. We have to have an excuse to get into the sack.
Unfortunately there are not enough characters left for me to tell you how clever I am.

Jan 29, 2013
I think that if the body didn't keep some of the body repairs for sleep time we would probably start to boil and die or we would have to move and think slow like turtles. Sleep seems to be a good mechanism that allows useful work during the waking hours. I have no proof of that but it makes sense to me.

Jan 29, 2013
What exactly is this study saying? All I get is, " If you incur a sleep debt, your body will signal a need to catch up on extra sleep... As you increase your sleep duration to recover from the debt, your ability to prolong wakefulness increases. Then, as prior wakefulness increases, sleepiness is inevitable, and a need for further sleep develops again." In other words, if you don't get enough sleep, you need to go to sleep or you will be tired. You will then sleep longer and feel better. After that, you don't need to sleep again. Sorry to be crass, but "duh!" I must be missing something here.

Jan 29, 2013
My grandfather (born in 1904) always said "You can't catch up on lost sleep." He also said "Pennzoil is full of abrasive minerals." So I guess he's 1 for 2.

Feb 03, 2013
The variable length sine wave fluctuations in sleep patterns is new to me. It would be nice to find out details on that and hypothesis explanations. Their conclusion that it's independent of so many factors, leaves me wondering what it is dependent on. The rest of the article seemed to confirm existing conclusions.

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