Researchers found that when people with Alzheimer’s and OSA are treated with CPAP, cognition and memory improves. This study was published in the November edition of the Journal of the American Geriatrics Society. They estimated that about 70-80% of Alzheimer’s patients have at least 5 apneas every hour. The authors concluded that CPAP may be an effective tool to improve cognitive skills if someone with Alzheimer’s also has OSA. They pointed out, however, that it’s unlikely that OSA causes dementia, and that the lowered oxygen levels and sleep fragmentation is what can aggravate poor cognition and memory loss.
I disagree with the last statement. The fact that 70-80% of Alzheimer’s patients have OSA is a very high figure. The minimum criteria for a sleep apnea diagnosis is 5 apneas or hypopneas per hour, and each episode has to last longer than 10 seconds. But what if someone stops breathing 25 times every hour, but wakes up only after 2 or 9 seconds? It doesn’t get counted at all! These are the people who are tired all the time and never get deep refreshing sleep, and it’s called upper airway resistance syndrome.
Also, sleep apnea doesn’t just occur all of a sudden when you’re older or gain weight. All modern humans are susceptible to various degrees, so it’s plausible that these same Alzheimer’s patients in the study already had at least some degree of a sleep-breathing problem for years, or even decades before the onset of Alzheimer’s.
If you take a look at the research literature, there are tomes of studies that link sleep apnea (and even snoring alone) with a much higher incidence of stroke (as well as heart disease). One recent study looked a MRIs of people with sleep apnea and found a significant increase in the number of small silent strokes (or lacunar infarcts). Another study showed that people with sleep apnea had significantly reduced blood flow rates to certain critical areas of the brain. Other studies have shown that the acoustic trauma from snoring can worsen carotid artery plaque formation. This is just a small sampling of studies that all suggests that the process of Alzheimer’s begins long before you develop symptoms. Add to this the fact that Alzheimer’s patients also have a higher incidence of depression and heart disease. And lastly, there’s a general consensus amongst Alzheimer’s researchers that this condition is a small vessel disease. Autopsy studies have revealed neurofibrilary tangles (NFTs) and senile plaques (SPs) in Alzheimer’s patients, but no one has figured out why or how these events occur. NFTs and SPs are also seen in other non-Alzheimer’s conditions as well.
All this goes back to my theory that all humans are on a continuum with regards to sleep-breathing problems. Of course, if OSA causes lots of mini-strokes over decades and once you become demented at age 80, treating your underlying sleep apnea will help you think better, but the damage has already been done.