The very nature of sleep apnea leads to short periods of time throughout the night when there is no oxygen moving throughout the body, a state called hypoxia.
When you’re not breathing, your brain doesn’t receive oxygen either. Because of this, sleep apnea is considered a risk factor for dementia. People who suffer from sleep apnea have been shown to have impaired memory and executive functions.
Research has also shown biomarker changes associated with the development of Alzheimer’s disease.
The Link Between Sleep Apnea and Dementia
A November 2020 study conducted by Monash University found a strong link between sleep apnea and dementia.
Results of the study showed that patients with severe obstructive sleep apnea also showed increases in a protein that builds up on arteries in the brain. These increases in protein buildup also increase the risk of developing dementia.
Thirty-four individuals were studied who had newly diagnosed and untreated obstructive sleep apnea. Twelve of the people included in the study were asymptomatic. Using PET scans of the brain and other measures of sleep and mood, it was determined that there was an overall lack of time spent in stage N3 sleep.
This type of sleep is directly involved in healing, repair, and regeneration for your body.
The lack of stage N3 sleep, oxygen dips, and frequent sleep arousals resulted in the body being unable to repair itself overnight properly. Long-term, this leads to memory loss, poor executive functioning, and dementia.
Sleep Apnea and Brain Damage
If you have obstructive sleep apnea, there is a higher chance of developing dementia. Long term, hypoxia to the brain causes damage, including –
- Difficulty focusing
- The trouble with decision making
- Slowed motor functioning, particularly with fine motor skills like writing or tying your shoes
- Developing dementia symptoms at an earlier age
- Other health conditions, including high blood pressure, diabetes, and stroke
There are many studies that show the effects of sleep apnea on the brain. A scientific review published in the journal Neurology looked at various links between sleep apnea and Alzheimer’s.
What they found was that people with Alzheimer’s disease were five times more likely to have sleep apnea than those without. They also found that over half of their participants with a dementia diagnosis experienced sleep apnea.
A second study found sleep apnea correlated with decreases in hippocampal volume and increases in lesions on the white matter of the brain. These changes are similar to those that occur with dementia and Alzheimer’s disease.
People with sleep apnea who have normal cognitive functioning have still been found to have delayed recall abilities and declines in executive functioning, the ability to plan, multi-task, and organize one’s behavior.
Several other studies found increased deficits in attention, visual-spatial abilities, and delayed memory retrieval.
Sleep Deficits and Dementia
Individuals with sleep apnea often have long-term sleep deficits. They don’t sleep long enough because they are woken up frequently throughout the night. Research has shown a U-shaped curve with regards to sleep length and cognitive decline.
What this means is that dementia can develop when you sleep too little or too much. That said, lack of sleep is associated with a much higher risk of developing dementia.
Earlier, we talked about dementia being related to a buildup of a protein in your brain’s blood vessels. Even one night of serious sleep loss raises the levels of this protein, and long-term build-up leads to Alzheimer’s.
With sleep apnea, your “slow-wave sleep,” or restorative sleep cycles, are disturbed, which plays a critical role in the retention of memories and learning new information.
Treating Sleep Apnea to Reverse The Damage
The studies showing a link between sleep apnea and dementia have all been completed on patients whose sleep apnea is untreated.
So while obstructive sleep apnea leads to symptoms of cognitive decline, reduces the amount of white matter in the brain, and increases plaques due to protein buildup, it’s important to note that treating sleep apnea has the potential to reverse these changes.
A small study completed in 2020 followed 17 men with severe sleep apnea. They were untreated prior to the study and showed significantly reduced volumes of white matter, impaired thought processes, impaired moods, and poor alertness.
These men were treated with CPAP therapy for 12 months to reverse their sleep apnea.
After just one year of CPAP therapy, the white matter damage in the brain was almost completely reversed. Cognitive thinking scores improved, along with mood, alertness levels, and quality of life.
A similar study looked at grey matter changes in the brain and found a similar result after only three months of treatment. Both of these studies found that the dementia-causing brain damage from sleep apnea was completely reversible with CPAP treatment.
Summary of Research Findings
It’s clear from the research that there’s a link between untreated obstructive sleep apnea and the development of dementia or Alzheimer’s.
What’s not clear is whether there is actually a causal link or if the lack of sleep caused by sleep apnea simply predisposes patients to similar cognitive symptoms to dementia. Here’s what we know:
- Individuals with sleep apnea develop cognitive impairments an average of 10 years earlier than individuals without sleep apnea.
- Sleep apnea is directly correlated with the development of Alzheimer’s at a younger age.
- Individuals who treat their sleep apnea using CPAP are able to reverse their cognitive decline and the brain damage caused by periods of hypoxia.
The studies showcased here don’t prove that sleep apnea causes dementia, but they do show a strong link between the two diagnoses.
In light of this link and the other health problems that sleep apnea can cause, it’s clear that diagnosing and treating sleep apnea is important to prevent further health problems.
It is certainly hopeful that brain changes can be reversed upon treatment. Regardless of how long sleep apnea has gone untreated, starting and maintaining treatment can reduce the risk of early dementia diagnosis.