I work every day at keeping my brain in good shape. I read, I play games with my kids (Words with Friends, anyone?), take supplements, you name it. I eat a diet that emphasizes brain food—including those omega 3s I wrote about recently. I also make sure to get plenty of sleep.
I’m working hard today so that my cognitive abilities stay strong decades down the road.
But living a healthful lifestyle doesn’t keep us free from worry about the long-term risks for cognitive decline and neurodegenerative diseases like dementia. Many of my patients who are moving through middle age talk with me about their fears of losing memory, mental clarity, and cognitive functions with age—and of their concerns about Alzheimer’s in particular.
There’s new research out about the link between sleep and Alzheimer’s I want to share with you, research that deepens our understanding of how poor sleep and Alzheimer’s disease are connected. Most of us probably know, or know of, someone who has been affected by Alzheimer’s. Unfortunately, the numbers bear that out. According to the Alzheimer’s Association, someone in the US develops Alzheimer’s disease every 65 seconds. Today, there are 5.7 million Americans living with this neurodegenerative disease—the most common form of dementia. By 2050, estimates predict that number will rise to 14 million.
What causes Alzheimer’s disease?
The tough answer is, we don’t yet know. Scientists are working hard to identify Alzheimer’s underlying causes. Though we don’t yet know why, what we do know is that the disease causes fundamental problems in the way brain cells operate.
Billions of neurons in our brains are constantly at work, keeping us alive and functioning. They enable us to think and make decisions, store and retrieve memory and learning, experience the world around us through our senses, feel our whole range of emotions, and express ourselves in language and behavior.
Scientists think there are several types of protein deposits that cause the degradation of brain cells, leading to the progressively more serious problems with memory, learning, mood and behavior– the hallmark symptoms of Alzheimer’s. Two of those proteins are:
- Beta amyloid proteins, that build up to form plaques around brain cells
- Tau proteins, that develop into fiber-like knots—known as tangles—within brain cells.
Scientists are still working to understand how plaques and tangles contribute to Alzheimer’s disease and its symptoms. With age, it’s common for people to develop some of these build ups in the brain. But people with Alzheimer’s develop plaques and tangles in significantly greater amounts—especially in areas of the brain related to memory and other complex cognitive functions.
There’s a growing body of research that indicates poor quality sleep and not getting enough sleep are linked to greater amounts of beta amyloid and tau proteins in the brain. One study released in 2017 found that in healthy, middle-aged adults, disruptions to slow wave sleep were associated with increased levels of beta amyloid proteins.
Daytime sleepiness is linked to Alzheimer’s-related protein deposits in the brain
A just-released study shows that excessive daytime sleepiness is linked to higher amounts of beta amyloid protein brain deposits in otherwise healthy older adults. Scientists at the Mayo Clinic set out in their study to answer a big question about causality: does build-up of beta amyloid protein contribute to poor sleep, or does disrupted sleep lead to the accumulation of these proteins?
The Mayo Clinic already had in progress a long-term study about the cognitive changes associated with aging. From that already-running study, scientists selected 283 people, who were over age 70 and did not have dementia, to investigate the relationship between their sleep patterns and their beta amyloid protein activity.
At the beginning of the study, nearly one-quarter—a little more than 22 percent—of the adults in the group reported that they experienced excessive daytime sleepiness. Being excessively sleepy during the day is, of course, a prime indicator you’re not getting enough sleep at night—and it’s a symptom associated with common sleep disorders, including insomnia.
Over a seven-year period, scientists looked at patients’ beta amyloid activity using PET scans. They found:
- People with excessive daytime sleepiness at the beginning of the study were more likely to have higher levels of beta amyloid over time
- In these sleep-deprived people, a significant amount of beta amyloid build-up occurred in two particular areas of the brain: the anterior cingulate and the cingulate precuneus. In people with Alzheimer’s, these two areas of the brain tend to show high levels of beta amyloid build up.
This study doesn’t provide a definitive answer to the question of whether it is poor sleep that’s driving amyloid protein build up, or the amyloid deposits that are causing sleep problems—or some of both. But it does suggest that excessive sleepiness during the day may be one early warning sign of Alzheimer’s disease.
The Mayo Clinic study lines up with more recent research that looked at the relationship between poor sleep and Alzheimer’s risk. Scientists at the University of Wisconsin, Madison investigated the possible links between sleep quality and several important markers for Alzheimer’s, found in spinal fluid, including markers for beta amyloid proteins and the tau proteins that lead to nerve-cell strangling tangles.
In this study, the scientists tested people without Alzheimer’s or dementia—but they specifically chose individuals who were at higher risk for the disease, either because they had a parent with Alzheimer’s or because they carried a specific gene (the apolipoprotein E gene), which is linked to the disease.
Like their counterparts at Mayo, the Madison researchers found that people who experienced excessive daytime sleepiness showed more markers for beta amyloid protein. They also found daytime sleepiness linked to more markers for tau proteins. And people who reported sleeping poorly and who had greater numbers of sleep problems showed more of both the Alzheimer’s biomarkers than their sound-sleeping counterparts.
The brain cleans itself of Alzheimer’s-related proteins during sleep
It was just a few years ago that scientists discovered a previously un-identified system in the brain that clears waste, including the beta-amyloid proteins associated with Alzheimer’s. (The University of Rochester Medical Center scientists who made this discovery named it the “glymphatic system,” because it functions a lot like the body’s lymphatic system in removing waste from the body, and is operated by the brain’s glial cells.) Scientists didn’t just identify the glymphatic system—a groundbreaking discovery in and of itself. They also found that the glymphatic system goes into overdrive during sleep.
When we sleep, the scientists discovered, the glymphatic system becomes 10 times more active in clearing waste from the brain.
This is some of the most compelling research yet to show the importance of healthy sleep to long-term brain health. When you sleep, scientists now think, your glymphatic system steps up its activity to remove potentially harmful debris that has collected over your waking day. If you sleep poorly or go without sufficient sleep on a regular basis, you risk missing out on the full effects of this cleansing process.
Irregular sleep wake cycles linked to Alzheimer’s
Another possible sleep-related early warning sign of Alzheimer’s? Disrupted sleep patterns, according to new research. Scientists at Washington University School of Medicine tracked the circadian rhythms and sleep-wake cycles of nearly 200 older adults (average age, 66), and tested them all for very early, pre-clinical signs of Alzheimer’s.
In the 50 patients who showed pre-clinical signs of Alzheimer’s, all of them had disrupted sleep-wake cycles. That meant their bodies weren’t adhering to a reliable pattern of nighttime sleep and daytime activity. They were able to sleep less at night, and inclined to sleep more during the day.
One important thing to note here: The people in the study who had disrupted sleep-wake cycles weren’t all sleep deprived. They were getting enough sleep—but they were accumulating sleep in a more fragmented pattern over the 24-hour day.
This study suggests that disrupted circadian rhythms may be a very early biomarker for Alzheimer’s, even in the absence of sleep deprivation.
When my patients share with me their worry about their long-term cognitive health, and their fears of Alzheimer’s, I understand. I’ll tell you what I tell them: the best thing you can do is to translate your worry into preventative action, and take care of yourself today, with the goal of lowering your risk for cognitive decline and dementia in mind. Looking at all that we know, it’s clear that getting plentiful, high-quality sleep is an important part of that action plan.