As people get older, they sleep less and wake up more frequently. In a recent review article, it was found that aging adults may be losing their ability to produce deep, restorative sleep. Furthermore, older people are likely paying for lost sleep both mentally and physically, the reviewers argue.
Older adults' sleep loss isn't due to a busy schedule or simply needing less sleep. As the brain ages, neurons and circuits in the areas that regulate sleep slowly degrade, resulting in a decreased amount of non- rapid eye movement (NREM) sleep. Since non-REM deep sleep plays a key role in maintaining memory and cognition, that’s a problem. And in the review, it has been said that 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 scientists apply to slumber. "Sleep duration--how much time you spend asleep--decreases as you get older," says one among the study co-authors. 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 NREM deep sleep, gets dramatically reduced as you get older. Even moving from one stage to another becomes less predictable and more disorganized.
This problem has long flown under the radar in sleep research. Older adults rarely report feeling sleepy or sleep-deprived on surveys but that may be because their brains are accustomed to being sleep-deprived every day. When researchers look for chemical markers of sleep deprivation, older adults have them in spades, and when researchers measure the brain waves of older adults, they often find that key electrical patterns in sleeping brains--such as "slow waves" and "sleep spindles"--are disrupted.
Perhaps even more distressingly, the changes in sleep quality start well before people notice that they are shifting to a more "early-to-bed-early-to-rise" schedule or are waking up in the middle of the night more often. The loss of deep sleep starts as early as the mid-thirties. 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.
Another surprising finding the authors address is the resilience of REM sleep to the process of aging--rapid-eye-movement (REM) sleep, where dreams occur. "It does decline, but it is nowhere near as dramatic as the decline in deep NREM sleep. The authors stress that there is variability between individuals when it comes to sleep loss. Women seem to experience far less deterioration in NREM deep sleep than men, even though the changes to REM sleep are about the same in those two genders. (Aging-related sleep loss hasn't been studied in trans and non-binary people yet.) Faster-than-average sleep deterioration may also be a key risk factor for neurodegenerative diseases like Alzheimer's and dementia.
Unfortunately, there currently aren't very many treatment options for people who are concerned about the loss of deep sleep. Standard "sleep hygiene" advice such as "Don't drink coffee in the late afternoon," "Avoid sleep-disrupting drugs like alcohol," and "Keep a regular sleep schedule" still applies. However, none of those measures will stop the process. Sleeping pill prescriptions are more common among older people, but sleeping pills sedate brains rather than restoring youthful sleep patterns.
Sleep decline is one of the most dramatic physiological changes that occurs as we age. 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.