Physical Decline Hastened By Too Little Deep Sleep

Main Category: Sleep / Sleep Disorders / Insomnia
Also Included In: Seniors / Aging
Article Date: 21 Jun 2008 - 7:00 PDT

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Too little deep sleep may accelerate the physical decline associated with old age, a study suggests. A team from the University of Chicago has presented what it describes as the first evidence that reduced slow wave sleep contributes to the decline in human hormone growth secretion - a key factor in the muscle wastage and increased body fat seen in older people.

Reductions in slow-wave sleep and a decline in the production of growth hormone are known to occur around the same time in the human lifespan. But little direct evidence linking the two processes has yet been produced.

The Chicago researchers studied the effects of sharply suppressing the slow-wave component of sleep in nine healthy, young, male volunteers who suffered no sleeping problems.

For baseline comparisons they measured growth hormone production from blood samples over a 24-hour period following two nights of normal sleep. Next, the researchers monitored the subjects' sleeping brain waves over three nights during which they used audio stimulation to prevent them entering deep or slow-wave (phase 3 and 4) sleep. They then measured growth hormone production.

Despite no difference in total sleep time, the time spent in deep sleep was reduced by an average of 90 minutes per night. The mean 24-hour production of human growth hormone fell from a control level of 863ng to 668ng after slow-wave sleep was reduced.

"We think this is the first evidence that reducing slow-wave sleep actually causes a decrease in human growth hormone secretion," stated lead researcher Dr Esra Tasali of the university's medical school.

"It also suggests that reduced slow-wave sleep could be contributing to falling human growth hormone production which leads to raised body fat and falls in lean body mass." The study was hailed by Dr Martica Hall, a bio-psychologist from the University of Pittsburgh who specialises in sleep and ageing.

"This is a small study, but a very elegant one, by one of the best research groups in the country in this field. We've suspected for a while that reducing slow-wave sleep has physiological effects. But this data actually shows this is the case, so it's quite exciting."

Written by Michael Day, sponsored by sanofi-aventis

SLEEP 2008 - Baltimore

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