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Tuesday, 15 August, 2000, 23:49 GMT 00:49 UK
Sleep linked to ageing
Asleep
People sleep less as they grow older
Scientists have discovered strong links between sleep and ageing.

A study by researchers at the University of Chicago found that sleep patterns change dramatically as people grow older.

These changes, they suggest, affect the body and contribute to ageing.

The researchers collected data from sleep studies carried out between 1985 and 1999 on 149 healthy men aged between 16 and 83 years.

They found that sleep deteriorates at two points in a person's life - between the ages of 16 and 25 and again between the ages of 35 and 50.

They report that while the total time spent asleep remained the same as young adults moved towards middle age, the type of sleep differed.

Their study shows that as young people grow older they spend less of their sleeping time in slow wave or deep sleep.

Total deep sleep decreases from nearly 20% of a normal nights sleep for those under 25 to less than 5% for those over 35.

They suggested this was important because it also had implications for a person's growth hormone secretion.

The researchers said that as deep sleep decreases so does growth hormone secretion and by the time a person is 35 it has fallen by about 75%.


Altered levels of certain hormones may be a consequence of sleep decay

Dr Eve Van Cauter, University of Chicago

Previous studies have shown that growth hormone deficiency can lead to obesity, loss of muscle mass and a reduced capacity to exercise.

By the age of 45, according to the study's authors, most men have completely lost the ability to generate significant amounts of deep sleep.

Hormones

Dr Eve Van Cauter, professor of medicine at the University of Chicago and one of the authors, said changes in sleep patterns may affect men's hormones.

"Our study maps out the chronology of age-related changes in sleep duration and quality and suggests that altered levels of certain hormones may be a consequence of sleep decay."

She suggested that clinical trials should be carried out in middle aged men in an effort to tackle growth hormone deficiency later in life.

"We begin estrogen replacement as soon as women enter menopause, not 20 years later," said Dr Van Cauter.

"If men go through 'somatopause' - a loss of growth hormone - between 25 and 45, why should we wait another 20 years to initiate treatment?"

The study also found that people sleep less as they grow older - declining by 27 minutes per decade.

They are also more likely to wake up during the night and for longer stretches at a time.

As people get older, they also experience less REM or dream sleep.

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See also:

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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