LONDON: Women live six or seven years longer than men because they sleep more deeply, according to US scientists.

Men who stay up late, and who toss, turn, count sheep, or who suffer from sleep apnoea — a respiratory condition — are at greater risk from diabetes, heart disease and other conditions probably because they sleep less well, said Alexandros Vgontzas of Pennsylvania State University.

He told the journal Chemistry and Industry that women’s mastery of the mattress was probably an evolutionary adaptation to the needs of child rearing. In effect, waking up for the 2 am feed was compensated for by a better kind of oblivion.

Professor Vgontzas and colleagues from the US National Institute of Health encouraged 25 volunteers to sleep peacefully for eight hours a night, for four days.

Then for the next eight days, the sleepers were woken after six hours. Blood hormone levels were continually sampled, and they were given vigilance tests every hours.

After one week of slight sleep deprivation, both men and women volunteers were drowsy, performed less well at the tests, and showed raised levels of interleukin-6. But men also showed great levels of tumour necrosis factor. Both hormones are involved in the development of insulin resistance, which can lead to obesity.

The women also slept better: they got around 70 minutes of deep sleep a night, while men only got 40 minutes on average.

Severe sleep deprivation can kill. The commonest remedy for illness, conversely, is sleep. But until now researchers had assumed that mild sleep deprivation was not a great health problem.—Dawn/The Guardian News Service.