Old people need just as much sleep as the young, but don't get it, a new study has found.
It's well-known the older a person gets, the less they are likely to sleep. But scientists in the US have found the sleep they're losing is the kind they need the most - the deep, restorative kind.
And the decline begins as early as the mid-30s.
"Sleep changes with aging, but it doesn't just change with aging; it can also start to explain aging itself," says Matthew Walker, who leads the Sleep and Neuroimaging Laboratory at the University of California.
"Every one of the major diseases that are killing us in first-world nations - from diabetes to obesity to Alzheimer's disease to cancer - all of those things now have strong causal links to a lack of sleep."
In other words, what ails us when we're old is not only made worse by our lack of sleep - it could be the result of it.
Reviewing previous research, the scientists found REM sleep - the kind that gives you dreams - hardly drops at all, but "slow wave" slumber is significantly disrupted.
"It's particularly dramatic in early middle-age when it starts to begin," says co-author Bryce Mander, also of the University of California.
"The difference between young adults and middle-aged adults is bigger than the difference between middle-aged adults and older adults."
But solving health woes that come with age isn't as simple as using sleeping pills. While prescriptions for sleeping pills are more common among the elderly, they work by sedating the brain, rather than restoring youthful, rejuvenating sleep patterns.
"More attention needs to be paid to the diagnosis and treatment of sleep disturbance if we are going to extend healthspan, and not just lifespan," says Dr Walker.
The findings were published Thursday in scientific journal Neuron.