"Sleep changes with aging, but it doesn't just change with aging; it can also start to explain aging itself," says review co-author Matthew Walker, who leads the Sleep and Neuroimaging Laboratory at the University of California, Berkeley.
‘As people get older, more attention needs to be paid to the diagnosis and treatment of changes in sleep patterns,which may be a risk factor for neurodegenerative diseases like Alzheimer's and dementia.’
"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. And all of those diseases significantly increase in likelihood the older that we get, and especially in dementia." Walker adds.
Why Do Older Adults Sleep Less?
In older adults, sleep loss is not due to a busy schedule. It is because of the degrading neurons and circuits in the sleep-regulating areas of the brain, as it ages. This reduces the non-REM sleep which is important for maintaining memory and cognition.
"There is a debate in the literature as to whether older adults need less sleep, or rather, older adults cannot generate the sleep that they nevertheless need. We discuss this debate at length in the review," says Walker. "The evidence seems to favor one side--older adults do not have a reduced sleep need, but instead, an impaired ability to generate sleep. The elderly therefore suffer from an unmet sleep need."
Aging leads to decline in almost every measure of sleep.
"Sleep duration--how much time you spend asleep--decreases as you get older," says study co-author Bryce Mander of University of California Berkeley. "Your sleep gets more fragmented as you get older. How much time you spend in individual stages of sleep, and the amount of time you spend in the deeper stages, in particular non-REM deep sleep, gets dramatically reduced as you get older. Even moving from one stage to another becomes less predictable and more disorganized."
When older people are surveyed regarding their sleep patterns, they rarely report feeling sleepy or sleep-deprived. This may be because their brains are accustomed to being sleep-deprived every day.
In older adults, the chemical markers of sleep deprivation found are in abundance, and their brain waves, both 'slow waves' and 'sleep spindles' are disrupted.
Sleep patterns begin to change by mid-thirties.
"It's particularly dramatic in early middle age when it starts to begin," says Mander. "The difference between young adults and middle aged adults is bigger than the difference between middle aged adults and older adults. So there seems to be a pretty big change in middle age, which then continues as we get older."
The sleep loss pattern varies between individuals. Women experience far less deterioration in non-REM deep sleep than men, though the changes to REM sleep are about the same in both genders.
This sleep deterioration may also be a key risk factor for neurodegenerative diseases like Alzheimer's and dementia.
Currently standard "sleep hygiene" advice include:
- not drinking coffee in the late afternoon
- avoiding sleep-disrupting drugs like alcohol
- maintaining a regular sleep schedule
Some people then resort to sleeping pills. Sleeping pills do not restore youthful sleep patterns, but rather they just sedate the brain.
"Sleep decline is one of the most dramatic physiological changes that occurs as we age, yet that demonstrable change is not part of the health conversation today," says Walker. "We need to recognize the causal contribution of sleep disruption in the physical and mental deterioration that underlies aging and dementia. 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."
The review of scientific literature is published in Neuron
- Matthew Walker et al. Sleep and Human Aging. Neuron; (2017) DOI: http://doi.org/10.1016/j.neuron.2017.02.004