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Sleep Apnea & Brain Aging: What the Science Shows
Millions of people fall asleep every night and wake-up, only to repeatedly stop breathing. This isn't merely snoring; in many instances, it's obstructive sleep apnea (OSA), a disorder with increasing amounts of documented evidence linking OSA to premature aging of the brain, cognitive decline, and an increased risk of cardiovascular problems.
Sleep apnea is common, usually goes unrecognized, and is often considered harmless. However, the evidence indicates that sleep apnea is anything but harmless. Additionally, there is mounting evidence demonstrating that successful treatment can significantly improve both the health of the brain and the overall health of an individual.
Why this is important
Repeatedly depriving the brain and cardiovascular system of oxygen and causing blood pressure spikes and disrupting sleep patterns causes cumulative damage to the brain and cardiovascular system. These stresses are believed to increase the rate of biological aging processes, especially in the brain.
Many individuals with OSA experience few obvious symptoms that exist during the day. Therefore, for many years, damage from OSA may occur before a person becomes aware of having the condition.
What Obstructive Sleep Apnea Actually Is
Obstructive sleep apnea occurs when the upper airway collapses into itself while a person is asleep and partially or completely blocks airflow. OSA can occur anywhere from time to time to more than 30 times per hour depending on the severity of the condition.
With each occurrence of an apneic event, the brain elicits a typical physiological response.
- Oxygen in the blood decreases
- Blood pressure rapidly increases
- The brain briefly awakens the body so that it can begin breathing again
In almost all cases, the individual does not fully awaken and typically does not recall the brief awakening. The stress response continues throughout the night as the cycle repeats.
What Happens in the Brain
Obstructive sleep apnea has been shown to cause measurable changes in the brain structure.
Some regions of the brain lose volume, which appears to be largely due to the loss of tissue sensitive to the loss of oxygen. Hypoxia (the lack of oxygen) is thought to contribute to the loss of tissue in the brain.
However, some regions of the brain appear thicker in individuals who experience more apneic events. This could represent early edema (swelling) or inflammatory responses that the brain undergoes in its attempt to compensate for the continued stress caused by the repeated hypoxic episodes.
These two types of changes are not mutually exclusive. The loss of oxygen and the fragmentation of sleep may be affecting different parts of the brain through different mechanisms. Many individuals experiencing these changes report little to no daytime symptoms.
Obstructive Sleep Apnea and Accelerated Brain Aging
Obstructive sleep apnea has been demonstrated to be a factor that accelerates biological brain aging.
Biological age of the brain is determined using machine learning algorithms to analyze the electrical activity of the brain. Researchers have compared chronological age with biological age of the brain.
Across numerous studies, individuals with sleep apnea showed brains that appeared to be biologically older than would be expected based on their chronological age.
This demonstrates that sleep apnea may be contributing to the acceleration of aging processes in the brain, rather than simply being comorbid with those processes.
Long-Term Effects on Cognitive Function and Brain Health
Large meta-analyses, including more than one million participants in 11 separate studies, have demonstrated that individuals with sleep apnea had approximately a 43% greater risk of developing dementia or a related cognitive disorder.
Additionally, sleep apnea has been associated with declines in various aspects of cognition:
- Attention
- Executive functioning
- Speed of processing
- Memory
While not everyone with sleep apnea will develop dementia, it appears that long-term risk for dementia-related conditions is higher in individuals with sleep apnea. Individuals interested in broadening their understanding of dementia prevention may also want to review blood pressure and dementia risk.
Effects Beyond the Brain
Obstructive sleep apnea impacts more than just the brain.
More than 75% of individuals with atrial fibrillation (a type of irregular heartbeat) have sleep apnea. Furthermore, the presence of sleep apnea appears to exacerbate the presence of atrial fibrillation.
Approximately 50% of individuals with sleep apnea have hypertension (high blood pressure), and the risk of hypertension increases with the severity of sleep apnea.
Cardiovascular disease risk is significantly elevated in individuals with sleep apnea. These risks are thought to be secondary to repeated drops in oxygen levels, sympathetic nervous system activation, and low-grade chronic inflammation.
Can the Damage be Reversed?
Fortunately, there is substantial evidence that treatment for sleep apnea can mitigate the damage to the brain and cognitive functions.
Continuous Positive Airway Pressure (CPAP) therapy prevents airway collapse during sleep. Studies examining the effects of CPAP therapy have demonstrated that, with consistent use, significant restoration of lost brain volume occurs in more severe cases.
Cognitive performance studies have also demonstrated improvements in multiple cognitive domains in individuals treated for sleep apnea for several months.
Diagnosis of Sleep Apnea
Unfortunately, many people with sleep apnea are unaware that they have sleep apnea.
The most common indicators of sleep apnea include:
- Habitual loud snoring
- Excessive daytime sleepiness
- Morning headaches
- Waking up gasping/choking
Screening for sleep apnea often begins with the completion of a questionnaire like the STOP-BANG.
Home sleep testing offers convenience, but measures fewer physiological signals and may underrepresent the degree of severity of the condition.
Laboratory sleep testing remains the gold standard for diagnosing sleep apnea. Laboratory sleep testing captures information regarding brain waves, sleep stages, respiratory effort, oxygen saturation, muscle activity, and heart rhythm.
Sleep Apnea Treatment Options Beyond CPAP (CPAP)
While CPAP is extremely effective when it is utilized consistently, there are significant limitations to long term adherence to CPAP therapy.
Additional alternatives may be considered depending upon how the patient's sleep apnea occurs; examples include positional therapy for individuals who experience sleep apnea while they sleep on their backs, and oral appliances that adjust the position of the jaw during sleep.
Surgical interventions can also be an option for selected patients.
In addition to medical treatments and surgical interventions, lifestyle modifications are particularly important. As stated above, weight loss is a significant modifiable risk factor for sleep apnea. Intervention studies have demonstrated that a considerable number of individuals are able to significantly reduce or eliminate their dependence on CPAP with consistent lifestyle changes.
Furthermore, medications that facilitate weight loss, such as GLP-1 based drugs, have been FDA approved for use in sleep apnea in conjunction with obesity. For additional information regarding GLP-1 and its relationship to longevity, see Micro Dosing of GLP-1 for Longevity.
Practical Take Aways
Sleep apnea is a chronic condition that does not only affect a person's ability to obtain a good night's sleep. Sleep apnea affects a person's brain structure and contributes to the acceleration of brain aging. Sleep apnea has been associated with an increased risk of developing dementia and cardiovascular disease.
A key takeaway from the majority of recent research is that much of this risk may be modified. Early detection of sleep apnea and successful treatment may result in improved brain health and cognitive function and potentially lead to longer life expectancy.
For individuals interested in increasing their chances of living a long healthy life by improving their cognitive resilience and preventing premature aging, identifying and treating sleep apnea is likely to be an effective method for achieving these goals. Improving overall sleep quality will also provide additional benefits for individuals seeking to improve their health through optimizing their sleep, as discussed in optimize your sleep for better health.