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Wednesday, 21 November, 2001, 09:19 GMT
Space travel 'causes sleep problems'
Astronauts take medication to help them sleep
Astronauts on extended missions into space may experience severe disruption to their sleep, scientists have found.

Researchers in the US have discovered that the brain's ability to control the body's sleep cycle is reduced when it is not exposed to the Earth's 'natural time cues'.

Their results could mean that longer missions into space, such as to Mars, could be jeopardised by performance problems caused by lack of sleep.

Jerry Linenger
Jerry Linenger spent five months in space
The team, led by Timothy H. Monk, professor of psychiatry at the University of Pittsburgh School of Medicine, based their findings on the sleep patterns of American astronaut, Jerry M. Linenger, during a five month journey into space.

24-hour rhythm

Dr Linenger lived aboard Russian Space Station Mir between January and May 1997. During that time he kept records of his sleep patterns.

His records revealed that he regularly went to bed at about 11.30pm and awoke at approximately 6am.

But towards the end of the five month period Dr Linenger had to force himself to keep to the routine and the amount and quality of his sleep reduced.

He woke more during the night and his temperature and alertness during the day also reduced.

Dr Monk and his team concluded that the endogenous circadian pacemaker (ECP), the part of the brain controlling the body's cycle of sleep, wakefulness, alertness, temperature and brain chemistry, was able to maintain its 24-hour rhythm for about 90 days after leaving Earth.

Quality and quantity

After that, the ability of the ECP, or the bodyclock, significantly diminished resulting in a drop in the quality and quantity of sleep.

Dr Monk said: "Man's ability to leave Earth and travel in space raises the question of whether the ECP, which evolved on a planet with a 24-hour rotation, would still function well when removed from all the natural time cues of the Earth.

"Our study show that human kind may need to find ways to trick the ECP into maintaining a strong 24-hour cycle if we are to succeed on longer missions."

Commenting on the findings, Professor Neil Douglas, chairman of the British Sleep Foundation, said: "The results are confirmation of what one would expect.

These results have implications for sleep and performance in night shift and rotating shift workers who similarly do not get cues from light dark cycles

Professor Neil Douglas
"They have implications for sleep and performance in night shift and rotating shift workers who similarly do not get cues from light dark cycles which are in phase with their sleep wake cycle.

"It is increasingly obvious that they sleep, perform and drive worse than permanent day shift workers."

Vicky Brightman, Space Now Co-ordinator at the National Space Centre, said: "Sleep problems for astronauts are one of several major problems which need to be overcome before longer missions into space could be successful.

"Scientists are constantly trying to find ways to overcome these problems and currently more than half the medication taken by astronauts when they are in space is to try and help them to sleep."

See also:

15 Aug 00 | Health
Sleep linked to ageing
19 Jul 00 | Health
Sleep 'vital to update memory'
26 Apr 00 | Health
'Hormonal battle' controls sleep
10 Feb 00 | Health
Brain 'battles sleep deprivation'
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