Sleep Apnea and Dementia: Exploring the Link

Sleep can become more elusive as we age and our bodies undergo changes, some of which are a normal part of aging and others not so much. One of the most common sleep disorders in older adults is sleep apnea, a condition where you stop and start breathing repeatedly during sleep. In fact, a study by the American Association of Sleep Medicine suggests that as much as 56% of adults over the age of 65 live with undiagnosed obstructive sleep apnea.⁴ Another chronic condition associated with age is dementia and almost 10% of adults over 65 have some form of dementia. This number skyrockets to 35% for those over 90 years old.⁹

There’s a link between sleep apnea and dementia as well. Research shows that older adults with sleep apnea tend to develop mild cognitive decline at an earlier age than their peers without sleep apnea.¹⁰ In this article, we’ll explore how sleep apnea and dementia are connected, discuss the best ways to prevent dementia and answer the question, “Does CPAP prevent dementia?”

Sleep apnea is a breathing disorder where you stop and start breathing multiple times during sleep. There are three types of sleep apnea: obstructive sleep apnea (OSA), central sleep apnea (CSA) and mixed sleep apnea. Out of all these, OSA is the most common form and it occurs when the airway becomes blocked or narrowed. This blockage can be caused by a number of factors such as increased fat or muscle around the neck, large tonsils, genetics and hormone changes that can affect the anatomy of the face and mouth. 

Learn more about these OSA risk factors to explore the relationship between sleep apnea and weight.

Dementia is a general term that describes a group of symptoms which are indicators of cognitive decline. These symptoms include memory loss, mood changes and a decline in reasoning, language and coordination. Like sleep apnea, dementia comes in different types. The most common type of dementia is Alzheimer’s, affecting more than 6.5 million Americans over the age of 65.¹ Alzheimer’s is caused by abnormal changes in the brain which include deposits of amyloid beta (Αß) protein in the gray matter of the brain, loss of neurons or brain cells, and the formation of tau protein tangles within neurons.

Research on the link between OSA and dementia is still ongoing but existing evidence suggests it’s related to the intermittent levels of low oxygen and poor sleep quality caused by OSA. In other words, sleep apnea and dementia are connected by their mutual links to sleep and hypoxia, or low oxygen in the tissues. 

When your airway is obstructed, your oxygen level drops but it rises again once your brain wakes you up. Sometimes this causes you to gasp or choke in your sleep. This intermittent exposure to low oxygen, followed by a restoration of oxygen, is harmful to your cells because it causes the production of reactive oxygen species (ROS) and increases inflammation. ROS injures cells and has been shown to cause brain cell dysfunction and death.²

Called oxidative stress, this process of cellular injury and destruction is observed in OSA patients. Cells need oxygen to function properly and cells in the brain are especially sensitive to low oxygen levels because they need more energy. When oxygen levels drop, some brain cells in the hippocampus and cerebral cortex die, causing problems with memory loss and difficulty paying attention.¹³ A 2002 study shows that markers of oxidative stress are present in the exhaled breath condensate of OSA patients, which explains why OSA patients can have trouble focusing and remembering things.³ 

So how is oxidative stress caused by intermittent low oxygen related to dementia? The brain is especially sensitive to oxidative stress and studies on Alzheimer’s show that the oxidation of proteins in the brain causes them to clump together and form fibrils. These fibrils are one of the characteristics of Alzheimer’s. Additionally, when the phospholipids that make up the brain membrane are oxidized, they produce aldehydes. These aldehydes degrade proteins, inhibit glycolysis (breakdown of sugar for energy) and disrupt the synthesis of nucleic acids and proteins.⁸ Numerous animal studies also show that these aldehydes damage neurons in the hippocampus, leading to problems with visuospatial memory.^5,6 

How Is Sleep Related to OSA and Dementia?

Sleep helps our brain flush out Αß proteins and prevents more of them from forming. Decreased REM sleep in particular is connected to more cognitive decline over time, suggesting a potentially higher risk of dementia if you have sleep apnea. People with OSA spend less time in REM sleep because they tend to have more apneas or breathing stoppages during this sleep stage. This is because our muscles relax during REM sleep, making it more likely for airway muscles and soft tissues to collapse and obstruct breathing.

A 2017 study of 321 older adults over 60 years of age illustrates this connection between the lack of REM sleep and dementia. The study followed the participants for 19 years and discovered that 32 participants were diagnosed with dementia later on in life. Analysis of the polysomnography data shows that those with dementia spent less time in REM sleep but their other sleep stages weren’t affected.¹²

However, a recent June 2023 study that examined the relationship between sleep architecture, OSA and cognitive ability revealed that sleep stages have no effect on cognition. In fact, the study found that good cognition is linked to better sleep consolidation and the absence of OSA.¹¹ OSA aside, preventing dementia is less about the amount of time you spend in each sleep stage and more about falling asleep and staying asleep with minimal awakenings. 

Untreated obstructive sleep apnea increases the risk of cardiovascular diseases, strokes, diabetes, and even contributes to oxidative stress that can damage brain cells and increase the chance of developing dementia. Since OSA and dementia are both related to repeated exposure to low oxygen levels, does treating one condition help prevent the other? Specifically, does sleep apnea treatment prevent dementia?

The verdict’s still out as there isn’t a lot of research on the effects of CPAP therapy on dementia. However, a 2023 review that examined 11 published journal articles on the effects of CPAP therapy on cognitive function suggests that CPAP use improves cognition.⁷ Unfortunately, the authors concluded that more research needs to be done before a definitive connection can be made.

We’ve all read a news article about how doing crossword puzzles helps prevent dementia, but lowering your risk of dementia involves more than just doing mental exercises. That’s not to say you shouldn’t do all you can to stimulate your brain, especially as you age; being mindful of your vascular health, avoiding head injury and controlling chronic medical conditions are important as well.

Keep Your Blood Vessels Healthy 

Anything that affects the circulation of blood to the brain and damages the blood vessels can increase the risk of vascular dementia and Alzheimer’s. Vascular dementia occurs when blood flow to the brain is disrupted, causing problems with problem solving and decreased reasoning. Although vascular dementia and Alzheimer’s are two different diseases, they are often seen together in older adults and share some common symptoms.

If you have a medical condition that affects circulation such as hypertension, diabetes and atherosclerosis, the hardening of arteries due to a buildup of plaque, it’s important to keep it under control. Smoking can also increase your risk of dementia as tobacco damages blood vessel walls and causes inflammation, increasing the risk of atherosclerosis. Even if you don’t have a chronic condition or a habit you’d like to quit, it’s still important to limit your intake of foods high in LDL, or low-density lipoprotein. Also known as the “bad cholesterol,” LDL causes plaque buildup in the arteries, causing narrowing that can lead to poor circulation.

Avoid Head Injury

Traumatic brain injury, or TBI, is an injury to the head that impacts cognitive function. The symptoms can occur immediately after injury or they can occur gradually over a span of days or weeks. Symptoms include nausea, loss of consciousness, confusion, difficulty remembering new events, memory lapses, lack of coordination and problems with vision and hearing. TBI can increase the risk of developing dementia, including Alzheimer’s, many years after the injury occurs. 

To protect yourself from TBI, it’s important to wear a helmet when playing contact sports and when biking, skating and rollerblading. Older adults should take care to avoid falls by having their vision checked regularly and using a walker if needed. It’s also a good idea to make sure your house is free of tripping hazards such as loose rugs and cords, regardless of your age. 

While it’s true that age and certain genetic factors increase the risk of OSA and dementia, there are many preventable measures you can take to lower your chance of developing either condition. Obesity is a major OSA risk factor so maintaining a healthy weight makes it less likely for you to stop breathing and experience low oxygen levels at night. It also protects you from other negative effects of sleep apnea such as increased inflammation, oxidative stress on tissues and cells and an overly active sympathetic tone that increases the workload on the heart and blood vessels. All of these are risk factors for dementia, suggesting a link between OSA and dementia.

Additionally, research indicates that you have a greater chance of cognitive decline if you have sleep apnea and fragmented sleep. By this logic, it’s no surprise that many of the best ways to prevent dementia—staying active, watching your weight, and quitting smoking—also lowers your risk of sleep apnea. And while there’s no cure for dementia, emerging research suggests that CPAP therapy may improve cognition, making it a possible treatment option for those with both sleep apnea and dementia. 

If you suspect you have symptoms of OSA and would like to get tested, RespShop offers convenient home sleep apnea testing with results interpreted by a board-certified sleep specialist. If you test positive for sleep apnea, the doctor will write you a prescription for a CPAP machine and send it straight to your email. It’s easy, fast, affordable and can all be done in the comfort of home. Learn more about our home sleep apnea testing service. 

Want to learn more about sleep apnea or CPAP therapy? Visit the RespShop Knowledge Base for tips on choosing the best CPAP mask, CPAP machine and mask reviews and expand your sleep apnea knowledge. Or, browse our selection of sleep apnea machines and CPAP supplies and feel free to contact us for assistance.    

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