Sleep apnea is a condition where breathing stops briefly during sleep. The brain doesn’t get enough oxygen and may not wake up until the person starts breathing again. This causes excessive daytime sleepiness and poor concentration.

It has hypothesized that people with sleep apnea have an increased risk of cognitive decline.

A new study examines the potential links between sleep apnea and Alzheimer’s disease.

In a new study, French scientists have scanned the brains of elderly people. They found an association between sleep apnea and the presence of amyloid plaques and other biological changes associated with inflammation and Alzheimer’s disease.

The scientists published their findings in the journal  Neurology JAMA.

Tracking changes in the brain

In this latest research, the scientists recruited 127 retired men and women over the age of 65 living in France and already enrolled in a Europe-wide clinical trial assessing the mental health and well-being of an aging population.

All participants answered questionnaires about their cognitive function and the quality of their sleep. Only people who had no symptoms of memory loss could participate in the study.

The researchers gave each person a wearable home device to record their sleep quality and breathing while they slept.

By measuring the frequency and duration of a decline in the participant’s nasal pressure, the researchers were able to divide the participants into two categories: those with and without sleep-disordered breathing.

The study team also tested participants’ memory and cognitive function, including executive function.

All participants underwent brain imaging scans, including magnetic resonance images (MRI) and positron emission tomography (PET) scans. A subgroup of 87 people also underwent an FDG-PET scan to measure glucose metabolism in the brain.

Link between sleep quality and Alzheimer’s disease

The study team found that around 75% of the participants had sleep apnea and there was a marked buildup of amyloid protein in their brains, a hallmark of Alzheimer’s disease.

They also found significantly higher gray matter volume and increased neural activity in brain regions associated with Alzheimer’s disease, including the cingulate cortex. These observations suggest inflammation in this area of ​​the brain.

When they analyzed the data, the researchers found no difference between self-reported memory problems and feelings of sleepiness between the two groups.

“At a time when clinical trials of Alzheimer’s disease treatments are not yet successful, the identification of risk factors and protective factors is of interest to a growing number of researchers.”

“Through the use of multiple brain imaging methods, this study allowed us to clarify the mechanisms explaining the links between sleep quality, risk of cognitive decline and Alzheimer’s disease,” explains the lead author. Dr. Géraldine Rauchs from the University of Caen, France.

“Although this does not mean that these people will necessarily develop the disease, they are at higher risk. In addition, effective solutions exist to treat sleep apnea. The detection and treatment of sleep disorders, in particular sleep apnea, will therefore be part of the arsenal to promote successful aging,” she explains.

This is the first study of its kind to use multiple brain imaging methods on a large group of participants from the general community.

Link between apnea and markers of Alzheimer’s disease

Researchers have found an association between sleep apnea and Alzheimer’s disease, which may point to a common underlying biological mechanism. However, the study was not intended to show causation or whether people with biological markers of Alzheimer’s developed symptoms of dementia.

The researchers plan to continue their work by investigating whether there is a difference between brain damage in men and women. They also plan to assess whether treating apnea can make a difference in brain changes.

Two other studies suggest sleep apnea is a risk factor for Alzheimer’s disease

Obstructive sleep apnea increases the risk of developing Alzheimer’s disease, possibly by increasing amyloid deposits in the brain.

It would also precipitate the first memory problems.

In 2017, a study showed that the severity of obstructive sleep apnea goes hand in hand with a higher level of amyloid (lesions characteristic of Alzheimer’s disease) in the brain. Thus, individuals with more apneas per hour had greater amyloid accumulation in the brain.

Obstructive sleep apnea affects 30-80% of older people.

« Several studies have suggested that sleep disturbances may contribute to amyloid deposition and accelerate cognitive decline in at-risk individuals, » said Dr. R. Osorio, MD, lead study author and professor of psychiatry at the Institute. New York University.

The study included 208 participants, aged 55 to 90, with normal cognition. The researchers performed lumbar punctures to collect cerebrospinal fluid (CSF) from the participants, then used positron emission tomography to measure amyloid deposits directly in the brain.

The results revealed that more than half of the participants had obstructive sleep apnea, including 36.5% mild and 16.8% moderate to severe. Of the total study sample, 104 participated in a two-year longitudinal study. A correlation has been observed between the severity of apnea and an increase in
amyloid deposits in the brain.

The study, however, did not find that the severity of apnea was a predictor of cognitive deterioration in these healthy older adults, which may seem surprising.

“It is clear that sleep is important for memory,” he adds. “Often people with sleep apnea don’t know. Their airways are temporarily blocked, causing them to wake up unconscious. Some people with sleep apnea can wake up at least 35 times per hour. »

According to the researchers, nocturnal continuous positive airway pressure ventilation, dental appliances, positional therapy and other treatments for sleep apnea may delay cognitive impairment and dementia in many older individuals.

In 2015, the same team showed in the journal Neurology that untreated sleep apnea advances the appearance of the first signs of memory loss by 13 years on average (77 years instead of 90).

It confirms a previous study (see below) which showed that older people with sleep apnea – signs of disturbed breathing during sleep – are more likely to be at risk of developing Alzheimer’s disease.

Sleep apnea also adversely affects the cardiovascular system by increasing the risk of heart disease, type 2 diabetes, high blood pressure and obesity. It would increase the risk of stroke.

This would explain, at least in part, its deleterious impact on the brain of the elderly.

The good news is that by treating these nocturnal breathing disorders with a positive pressure mask, its deleterious effect disappears.

2470 medical records of people aged 55 to 90 participating in a study on Alzheimer’s disease were analyzed.

The fact that there is a correlation between sleep apnea and Alzheimer’s disease does not mean that there is a causal link.

Sleep apnea would affect, among the elderly, one in two men and one in four women, many of whom are unaware of it.

People with untreated sleep apnea snore loudly, stop breathing in the middle of the night, and feel tired during the day.

Sources. RA Sharma et al. Obstructive Sleep Apnea Severity Affects Amyloid Burden in Cognitively Normal Elderly: A Longitudinal Study. American Journal of Respiratory and Critical Care Medicine, 2017. Osorio RS et al. Alzheimer’s Disease Neuroimaging Initiative. Sleep-disordered breathing advances cognitive decline in the elderly. Neurology, 12;84(19):1964-71, 2015.