In an age where we’re busier than ever and bombarded with information 24/7, many of us complain we don’t get enough sleep.

But getting too much shut-eye could actually be bad for your health, an expert has warned. ‘The lowest mortality and morbidity is with seven hours,’ says Shawn Youngstedt, a professor at Arizona State University Phoenix, who studies sleep duration.

‘But eight hours or more has consistently been shown to be hazardous,’ he told the Wall Street Journal. Just last month a study of almost 9,000 people found those aged 50 to 64 who slept for less than six hours a night–or more than eight–had worse memories and decision-making abilities.

But brain power was only reduced for older adults of 65 to 89 if they slept too long, say the University of Warwick researchers. Recent research published in the Journal of Clinical Sleep Medicine adds to the argument we may not need as much sleep as we think, writes WSJ journalist Sumathi Reddy.

When five adults lived for two months in ‘Stone Age-like conditions’ – no clocks, electricity or running water–they got on average 1.5 hours extra sleep than usual and fell asleep two hours earlier. But they still only averaged 7.2 hours a night, he writes. And most of us are probably getting more sleep than we strictly need–we’ve just convinced ourselves we’re sleep deprived, says sleep neuroscientist Professor Jim Horne, of Loughborough University.

He believes that far from us all being exhausted, ‘things have never been better’. Unlike the typical worker from 150 years ago, who toiled for 14 hours a day, six days a week and went home to a crowded, flea-infested bed, most of us sleep perfectly adequately. There have been several large studies over the past 40 years into how much sleep people actually get. The findings show that the average healthy adult sleeps for seven to seven-and-a-half hours a night.

Professor Horne, author of the book ‘Sleepfaring - A Journey Through The Science Of Sleep’, adds the much-repeated ‘fact’ that our ancestors used to sleep around nine hours is a myth. He says it 1913 study by researchers in California, which found that children aged eight to 17 slept for this amount of time. ‘There is a lot of fear-mongering about the so-called dangers of lack of sleep-but, in fact, the biggest danger of not having adequate sleep is having an accident, such as falling asleep at the wheel of a car.’

And which sex needs more sleep? Women–because their brains need more time to recover from the wealth of multi-tasking they do each day. The Duke University scientists, in North Carolina, found women who are sleep deprived often suffer from depression and become angry.