oka mam dalej :D tym razem : www.guardian.co.uk / zad. 10:
Body suffers symptoms of age with too little sleep
Sarah Boseley, Health Correspondent
Friday October 22, 1999
The Guardian
Sacrificing sleep to longer working hours and nights on the town could bring about changes in the body similar to ageing, according to new medical research.
A study of the effects on the body of the sort of sleep-debt that is increasingly common at the end of the 20th century has had startling results. Although the study was small - 11 young men aged between 18 and 27 took part - it found "striking alterations" in the way their bodies functioned, according to a report in this week's Lancet medical journal.
The Chicago-based scientists found that successive nights of four hours' sleep took its toll on the metabolism and endocrine (hormonal) functioning of the body. These alterations "mimic some of the hallmarks of ageing". The scientists suggest that chronic sleep loss could increase the severity of age-related diseases such as diabetes and high blood pressure.
They also suggest that young, healthy adults may need more than the standard night's sleep. Their volunteers biologically performed better when they had slept for more than eight hours.
Karine Spiegel and colleagues from the department of medicine of the university of Chicago write that it has become common for people to cut back on their sleep. What is considered normal average sleep duration has decreased from about nine hours a night in 1910 to about 7.5 hours now. Many shift workers sleep an average of five hours a night on working days. Margaret Thatcher was famous for firing on all cylinders after only five hours sleep a night.
It is generally held that sleeping less does you no harm, they say, as long as you get the core four to five hours of non-REM (non-rapid eye movement) sleep. There has been an assumption that sleep is intended to repair and refresh the brain and no studies have previously looked specifically at the effect sleep-deprivation has on the body.
The 11 young men slept eight hours a night for three nights, then four hours for six nights and then spent 12 hours a night in bed for a further week to recover from the sleep debt. The six nights of little sleep had a noticeable effect on their bodies.
"Less than one week of sleep curtailment in healthy young people is associated with striking alterations in metabolic and endocrine function," they say. Sleep debt "could have long-term adverse effects on health". Basic metabolic functions, such as processing and storing carbohydrates and regulating hormone secretion, were affected.
Eve Van Cauter, who led the study, said: "We suspect that chronic sleep loss may not only hasten the onset but could also increase the severity of age-related ailments such as diabetes, hypertension high blood pressure, obesity and memory loss."
Tests showed that the volunteers underwent profound alterations of glucose metabolism during sleep deprivation, in some cases resembling patients with type-2 diabetes. At the peak of sleep loss they took 40% longer than normal to regulate their blood sugar levels after a high carbohydrate meal. Their ability to secrete and respond to insulin fell by about 30%. A similar decrease in acute insulin response is an early warning of diabetes.
Sleep deprivation altered the production and action of other hormones besides insulin, dampening the secretion of thyroid-stimulating hormones and increasing blood levels of the stress hormone cortisol, especially in the afternoon and evening.
Raised cortisol levels in the evening are typical of much older people and thought to be related to age-related health problems, such as insulin resistance and memory impairment.
All these abnormalities faded away during the recovery period, when the volunteers spent 12 hours in bed.