Researchers at Wheaton College in Illinois have found that the effects of poor sleeping habits could be even more severe than previously thought
At the Alzheimer’s Association International Conference in London, researchers at Wheaton College presented three studies that showed significant correlation between interrupted sleep and Alzheimer’s disease.
Specifically, the studies showed that breathing disorders associated with interrupted sleep such as sleep apnoea can see an increase in the accumulation of biomarkers for Alzheimer’s. They found that dental appliances and CPAP machines used to force air into the airways can help slow the dementia process.
Hypopnea and sleep apnoea (under-breathing and not breathing whilst sleeping respectively) are common conditions worldwide, with the most common form — obstructive sleep apnoea — effecting 3 in 10 men and a fifth of women. Symptoms tend to appear during mid-to-late adulthood, before clinical signs of Alzheimer’s.
Sleep apnoea occurs when the upper airway closes during sleep whilst breathing efforts continue. This can wake sufferers up sometimes 50 or 60 times a night, which interrupts the vital stages of sleep.
What did the studies find?
The first of Wheaton College’s studies examined 516 cognitively normal adults between the ages of 71 and 78. Over a three-year period, those with sleep-disordered breathing had greater increases in one of the biomarkers (beta-amyloid deposits), regardless of whether they had the APOE-e4 gene which is considered an Alzheimer’s risk factor.
The second study found a connection between obstructive sleep apnoea and increases in amyloid build up in older adults with mild cognitive impairment.
The third and final study found the same connection in both cognitively normal and mild cognitive impairment patients. People who repeatedly jolted awake during the night showed immediate spikes in their amyloid levels.
What do these results suggest?
One of the Wheaton College researchers, Megan Hogan, pointed out that other examples of research on the topic have found that the brain clears deposits of amyloid plaque during sleep, so it could be that apnoea prevents this process from being carried out effectively.
She said: “During sleep… your brain has time to wash away all the toxins that have built up throughout the day. Continually interrupting sleep may give it less time to do that.”
Hogan also said that repeatedly depriving the brain of oxygen through apnoea may contribute to a build up in amyloid, as oxygen regulates an enzyme which plays a role in creating amyloid.
Ronald C. Peterson, director of the Mayo Clinic Alzheimer’s Disease Research Centre and the Mayo Clinic Study of Aging, explained that the clearing of amyloid from the brain is likely to occur in the deepest stages of sleep.
He said: “If you’re only making it to Stage 1 or Stage 2 [of the sleep cycle], and then you start choking or snoring or whatever, and you wake yourself up and you do it again and again, you may not even be aware of it, but you… may be accumulating this bad amyloid in the brain rather than clearing it.”
The studies did not clarify whether the relation between apnoea and dementia is causative, but director of scientific programs and outreach at the Alzheimer’s Association Keith N. Fargo said that either way, it shows the importance of a healthy sleep cycle.
“Ultimately it doesn’t matter what the direction is for this to have an effect on your life,” said Fargo. “If you’re waking up your partner multiple times a night or you’re tired all day, then you really, really need to go get checked by your doctor, because it could be a sign of something serious. Or if it’s not, just treating the apnoea could help with your day-to-day cognition.”
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