While the cause of Alzheimer’s disease remains a mystery, amyloid plaques that are toxic to brain cells are known indicators of the disease. A team of researchers from Australia and Iceland has found that these plaques start in the same place and spread in the same way in the brains of people with obstructive sleep apnea, as in those with Alzheimer’s.
Obstructive sleep apnea is a serious condition that occurs when a person’s breathing is repeatedly interrupted during sleep. It is increasingly common, affecting more than 936 million people worldwide and up to 30% of elderly people.
Alzheimer’s is the most common form of dementia, affecting up to 70% of all people with dementia, with age the biggest risk factor for developing the disease.
“We know the two diseases are related, but what drives the connection is still unclear,” said Professor Stephen Robinson, a scientist in the School of Health and Biomedical Sciences at RMIT University and the Institute for Breathing and Sleep at Austin Health.
“We know that if you have sleep apnea in mid-life, you’re more likely to develop Alzheimer’s when you’re older, and if you have Alzheimer’s you are more likely to have sleep apnea than other people your age.”
“The connection is there but untangling the causes and biological mechanisms remains a huge challenge.”
“Our study is the first to find Alzheimer’s-like amyloid plaques in the brains of people with clinically-verified obstructive sleep apnea.”
“It’s an important advance in our understanding of the links between these conditions and opens up new directions for researchers striving to develop therapies for treating, and hopefully preventing, Alzheimer’s disease.”
Professor Robinson and colleagues investigated the extent of Alzheimer’s-like indicators in autopsy tissue from the hippocampus of 34 people and the brainstems of 24 people with obstructive sleep apnea.
The researchers looked for both amyloid plaques and neurofibrillary tangles, another known indicator of Alzheimer’s disease.
In Alzheimer’s disease, plaques and tangles first appear in a nearby cortical area and then move into the hippocampus, before spreading to the rest of the cortex.
While the team found both plaques and tangles in the brains of people with sleep apnea, the plaques showed a stronger association with severe sleep apnea.
“In cases of mild sleep apnea, we could only find plaques and tangles in the cortical area near the hippocampus, precisely where they are first found in Alzheimer’s disease,” Professor Robinson said.
The findings were published in the journal Sleep.
Jessica E. Owen et al. Alzheimer’s disease neuropathology in the hippocampus and brainstem of people with obstructive sleep apnea. Sleep, published online September 21, 2020; doi: 10.1093/sleep/zsaa195