Dragging a teenager kicking and screaming out of bed too early on a Sunday morning could be bad for their health. Scientists have shown that a weekend lie-in is more than lazy indulgence and could be vital for well-being.
Tests on volunteers showed that the occasional sleep-in provides an invaluable antidote to the harmful effects of sleep deprivation. The findings will be welcome by all those lucky enough to be able to enjoy an extra hour or two of slumber on Saturdays and Sundays.
It came as another study warned of the dangers of persistently sleeping too much - and showed that people who regularly get more than seven hours every day are putting themselves at risk of heart disease.
Dr David Dinges, of the University of Pennsylvania School of Medicine in Philadelphia, who conducted the first study, said: ‘The additional hour or two of sleep in the morning after a period of chronic partial sleep loss has genuine benefits for continued recovery of behavioural alertness. The bottom line is that adequate recovery-sleep duration is important for coping with the effects of chronic sleep restriction on the brain.’
Inadequate sleep interferes with the way people think, handle stress and keep their emotions in check. It can also disrupt the immune system, increasing the risk of infection.
In the study, 142 adults with an average age of 30 were restricted to four hours in bed from 4am to 8am for five consecutive nights. At the end of the week, the volunteers were assigned to one of six ‘doses’ of a single night’s ‘recovery sleep’ - ranging from zero to ten hours. Another 17 made up a comparison group who spent ten hours in bed nightly.
As expected, the test performance of the sleep deprived volunteers was consistently worse than that of the well-rested control group. But just one lie-in after a week of sleep deprivation improved mental faculties - and the longer the lie-in, the more alert they become.
However, even after ten hours in bed, sleep-restricted participants still had worse scores than the control group for attention lapses, poor reaction times, and fatigue.
Meanwhile, the second study showed that seven hours is the ‘perfect’ amount of sleep. Researchers at West Virginia University showed that sleeping fewer than five hours a day - including naps - doubles the risk of being diagnosed with angina, coronary heart disease, heart attack or stroke.
But sleeping more than seven hours increases the risks of cardiovascular disease too, the researchers found. Researcher Dr Anoop Shankar was unable to explain why length of sleep is linked to heart problems, but past studies have shown that sleep deprivation can increase blood pressure and diabetes.
