Lack of sleep may speed ageing process

Lack of sleep can cause chemical changes in the body

Sleep deprivation has a similar impact on the body to the ageing process and may increase the severity of age-related chronic disorders such as heart disease and diabetes, researchers have found.

During this century, the average number of hours people spend asleep per night in more developed countries has decreased from nine hours to seven-and-a-half hours.

The change has been made to accommodate increased demands of work and more leisure activities.

Millions of shift workers average less than five hours' sleep per day.

Scientists have traditionally believed sleep was beneficial only for the brain.

But a team from the US Department of Medicine in Chicago, investigated whether sleep debt can alter metabolic and hormonal functions.

Professor Eve Van Cauter, who led the study, said: "We found that the metabolic and endocrine hormonal changes resulting from a signficant slep debt mimic many of the hallmarks of ageing.

"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, obesity and memory loss."

The Chicago team tested the effect of different amounts of sleep on 11 young men.

The participants were allowed eight hours per night for the first three nights of the study.

It is thought eight hours is the amount of sleep required for the body to be fully rested.

On the following six nights, the participants were restricted to four hours' sleep a night.

Finally, they were allowed 12 hours' sleep a night for the concluding seven nights of the study.

Measurements of body function

The investigators took measurements during the day of glucose tolerance, cortisol concentrations (a hormone that helps to regulate blood sugar concentrations), heart rate, sleepiness, and the impact on the production of various hormones.

Following the period of sleep deprivation, the researchers found subjects had higher levels of glucose and cortisol in their blood.

They also took up to 40% longer than normal to regulate their blood sugar levels after a high carbohydrate meal.

Sleep deprivation also led to an increase in the activity of the sympathetic nervous system, which controls many of the body's "involuntary" functions.

Dr Tom Mackay, a consultant respiratory physician at the Scottish National Sleep Centre at Edinburgh Royal Infirmary, said the research showed sleep deprivation provoked a typical stress response in the body, characterised by raised cortisol and glucose levels.

He said persistently high levels of glucose increased the risk of developing diabetes, heart disease and strokes.

But he said: "The difficulty is that nobody really knows what the main risk factors for heart disease and stroke are.

"It may be that sleep deprivation is an important risk factor or just one of a number of different factors.

"This is interesting research, but it would be a big jump to conclude that sleep deprivation is responsible for such chronic diseases."

Dr Mackay said the amount of sleep people required varied between individuals.

The important thing was to feel thoroughly rested after waking up.

In many cases the quality of sleep was more important that the quantity, he said.