According to the polls, two-thirds of American seniors—about 37 million people—are plagued by sleep problems. The consequences pose significant risks:
• Daytime sleepiness and fatigue, which leads to a lack of exercise that in turn may worsen weight problems, diabetes, and difficulty moving around.
• Depression, which can both lead to sleep problems and be a result of them.
• A weakened immune system, with an increased likelihood of disease.
• Heightened pain sensitivity, making sleep even more difficult.
• Nighttime falls and accidents.
Sleep problems often lead to cognitive
confusion and problems with memory
as well. This is particularly scary for older people. By comparison, poor sleep seems less important. Lots of seniors complain about memory lapses, though sometimes they take care to keep quiet about it. You start to tell a friend about a film you enjoyed—but you can’t come up with the title. You walk into the living room and suddenly stop, confused about what you were looking for. You get a beeper gadget to help you find your car keys.
These glitches are disconcerting, but in most cases they’re perfectly normal. Still, it’s hard not to wonder and worry that they might be early signs of Alzheimer’s or dementia.
SOMETHING MUST BE HAPPENING IN THE BRAIN!
It is well established that a specific brain region shrinks in old age. Called the hippocampus, it is deeply involved in the formation and retrieval of new memories. But not exclusively. The prefrontal cortex—the prominent area so closely associated with our human identity—also tends to lose volume as we age. Significantly, the prefrontal cortex is also vitally concerned with quality sleep.
Now a team of researchers led by Dr. Bryce Mander at Berkeley has provided evidence to directly link sleep problems, memory decline, and the prefrontal cortex. Their study, published in the January 27 online edition of Nature Neuroscience, compared a group of seniors to a group of young adults of college age. The medial prefrontal cortex was about one-third smaller and the amount of high-quality deep (“slow-wave”) sleep up to three-quarters less. The scores on a memory test were also lower, both in the evening and much more so the following morning.
How should we interpret these new findings? The researchers propose that atrophy in the prefrontal cortex interferes with deep sleep. The lack of deep sleep, in turn, is responsible for the deficits in memory storage and retrieval. Sounds reasonable, but it is only one of several possibilities.
The study did not address the issue of why the medial prefrontal cortex, in particular, shrinks with age. Consider that this crucial brain area might itself be affected by the loss of quality sleep. That would create a feedback loop:
• Age-associated sleep disturbance impacts the cortex.
• The resulting cortical shrinkage intensifies the sleep disturbance.
• The intensified sleep disturbance adversely affects memory.
If such a feedback loop exists, with an ultimate effect on memory, we would need new studies to confirm that sleep problems directly affect the cortex. Then we would need to show that improving sleep slows the neural deterioration. Those would of course be breakthrough studies if they had positive results.
CHRONOTHERAPY FOR SLEEP—AND MEMORY?
Speculation aside, there is plenty of evidence that several sleep difficulties associated with aging can be dramatically improved by steps that adjust the inner clock. Methods with promise include bright light therapy, dawn and dusk simulation, and low-dose melatonin.
Improving sleep without sleeping pills is a big enough benefit to merit using these tools of chronotherapy. But there is more. When patients with dementia were treated with enhanced light during the day and melatonin in the evening, nighttime sleep interruptions decreased, daytime mood improved, and cognitive decline slowed. This landmark study from The Netherlands certainly suggests positive feedback from quality sleep on brain function—possibly even brain structure.
We are not claiming that you can improve your memory by treating your sleep problems, even though that makes sense. We know that deep sleep is important to memory formation and retention. Chronotherapy research has produced evidence-based, drug-free ways to enhance quality sleep. Someday soon we will know more about how the brain benefits. Whatever the mechanisms prove to be, we are confident that improving sleep will enhance the process.
We talk about types of elderly sleep disturbance and how to deal with them in Chapter 14, “In Later Years,” of Reset Your Inner Clock. Topics include Age and Poor Sleep; Drugs, Light, and the Eye; Fixing Light Loss; Outdoors and In; “Early to Bed…”; Alzheimer’s and the Inner Clock; Shedding Light on Parkinson’s; Melatonin and Aging; What About Naps?; and Steps to Take.
Michael and Ian are co-authors of the 2013 Penguin paperback, Reset Your Inner Clock. They invite you to follow them on Twitter for news updates, opinions, and challenging Q-and-A’s. If you want to stay on top of body-clock matters, light therapy, and more — and take advantage of confidential, online self-assessments of inner clock time, depression, and seasonality — you should become part of the nonprofit Center for Environmental Therapeutics community. Email PTuser@cet.org so we can stay in contact.