Medically reviewed by
Dacelin St Martin, MD
Triple board-certified in Sleep Medicine,
Internal Medicine, and Pediatrics.
Sleep disorders ultimately result in a lack of high-quality sleep, which is attributed to many positive outcomes, including better health and greater cognitive function.
For decades, studies have highlighted how sleep disorders, such as insomnia  and obstructive sleep apnea (OSA), impact the elderly, shifting research towards understanding the link between such conditions and common underlying comorbidities in the elderly, such as dementia.
Despite research finding no clear relationship between sleep disorders and dementia, recent findings suggest that OSA, in particular, is closely associated with dementia and can potentially be used as a predictor for dementia occurrence.
Why is Sleep Important for our Brains?
Sleep is essential in retaining new information – whether it’s something we’ve learned, a memory we want to cherish, or reminding ourselves to take the bins out in the morning. The processes in which our brains allow us to retain such information occur throughout all sleep cycle stages, with REM sleep playing a key role.
Any disruptions in sleep through conditions such as OSA can result in the build-up of toxins in the brain responsible for conditions associated with cognitive declines, such as dementia.
What is Obstructive Sleep Apnea (OSA)?
OSA is an increasingly common sleep disorder that causes the repeated collapse of the upper airway during sleep, resulting in one’s breathing periodically stopping and starting throughout sleep. With each pause, the sleep pattern shifts from deep to light sleep.
Physiological effects are displayed, such as snoring and upper airway dilator muscle dysfunction, leading to a lack of sleep, low arousal threshold, and increased sleepiness throughout the day. There are three main types of OSA, including:
- Obstructive Sleep Apnea (OSA) occurs due to an obstruction caused by the collapse of the upper airway structures.
- Central Sleep Apnea (CSA) occurs when signaling pathways between the brain and muscles involved with breathing are disrupted and is often caused by a central nervous system disorder.
- Complex or Mixed Sleep Apnea (CompSAS) manifests as unobstructed apnea, quickly followed by upper airway obstruction.
The Link Between OSA and Dementia
Studies have shown an association between the lack of sleep and increased levels of proteins attributed to Alzheimer’s disease.
In addition to memory loss and increased agitation levels, many of those with dementia often find sleeping difficult. Add on the burden of OSA, and the link between sleep problems and dementia becomes a growing concern for our elderly society.
While the mechanisms of OSA are now better understood, the processes behind dementia are still widely unknown, thus making the management of those with the condition a considerable challenge.
As well as being far more prevalent in the elderly, particularly in older men, OSA has been linked to cognitive decline and dementia.[10,11,12]
The mechanisms that characterize OSA may contribute to an increased risk of dementia and exacerbate or worsen existing cognitive impairment. Such mechanisms include:
- Sleep Fragmentation: OSA results in sleep fragmentation, whereby an individual periodically wakes up throughout the night and is, therefore, unable to obtain sleep sufficient to maintain physiological and psychological function.
- Sleep Disruption: A recent study has found that the induction of OSA through the withdrawal of CPAP exclusively during REM sleep resulted in partial learning difficulties.
- Cardiovascular Outcomes: OSA is attributed to several cardiovascular comorbidities, including high blood pressure, stroke, high cholesterol, and an increased risk of heart disease. These conditions can contribute to an individual’s likelihood of developing vascular dementia, which has recently been linked to the etiology of Alzheimer’s disease.[16,17]
Does Treating OSA Reduce the Risk of Dementia?
Adequate treatment of OSA, including continuous positive airway pressure (CPAP), can improve sleep and mood and slow cognitive decline. A new study found that people who used CPAP were less likely to be diagnosed with dementia or mild cognitive impairment over the next three years compared to those who did not use CPAP.
These significant findings stress the impact of sleep on cognitive function, thereby further strengthening the link between OSA and dementia, shining a light on the possibilities of managing diseases of cognitive decline in the future.
What’s the Takeaway?
Additional research is necessary to confirm the protective role of CPAP therapy in preventing or reducing short-term dementia risk in the elderly population. Effective sleep apnea management can offer new opportunities to improve cognitive outcomes in older adults.
Those troubled by disrupted sleep due to OSA should contact their healthcare provider to commence appropriate treatment.
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