It is the boast of company executives and busy parents who pack the most into their days.
But getting by on little sleep may not be a sign of competence – rather, it could be because the brain is showing signs of age.
A review found that older people need just as much sleep as the young. However, they miss out on it because the areas of the brain that regulate sleep degrade over time.
The neurons and circuits we need to rest effectively break down gradually, resulting in less non-REM sleep. This is the dreamless, deep stage of sleep which allows us to wake refreshed.
It had previously been thought that adults needed less rest from middle age because they seemed less affected by losing it. But US scientists think they may simply have adjusted to compensate.
Professor Matthew Walker, whose team at the University of California, Berkeley, looked at numerous studies, said: "There is a debate whether older adults need less sleep, or rather, they cannot generate the sleep they nevertheless need. The evidence seems to favour one side – older adults do not have a reduced need, but instead they have an impaired ability to generate sleep."
We start losing sleep in our mid-thirties, but the problem becomes considerably worse from the age of 40 – when people find themselves taking longer to drift off and being woken more easily.
A quarter of adults report daytime sleepiness severe enough to spoil their everyday plans. Around one in ten aged 55 to 64 say they are forced to take daytime naps.
The review – published in the journal Neuron – states that the drive to sleep therefore appears to remain the same as we age.
And while sleep-deprivation causes less of a drop in performance among older adults than young, older people often perform considerably worse under rested conditions.
As a result, the team raises concerns that lack of sleep could lead to hefty mental and physical costs. Being deprived of rest has been linked to conditions such as Alzheimer’s, type 2 diabetes and cancer.
Professor Walker added: "Sleep changes with ageing, but it can also start to explain ageing itself.
"Major diseases killing us in first-world nations – from diabetes to cancer – now have strong causal links to a lack of sleep. And all of those diseases significantly increase in likelihood the older we get, especially dementia."
THE GENE KEEPING US AWAKE AT NIGHT
Ageing, stress and spending too long at the computer are not the only reasons for a bad night’s sleep.
Scientists believe that genetics could also play a part – and have identified a gene that is apparently to blame.
US researchers found that when the FABP7 gene mutates, it causes people to sleep fitfully and wake up during the night. In experiments, mice slept badly when it was removed. A study of 300 Japanese men found 29 with a variant of the gene also had worse sleep and woke more often.
Jason Gerstner, author of the study from Washington State University, said it was important to understand the function and processes behind sleep.
However the study, published in Science Advances, stresses that other genes are almost certainly involved.