Study links sleep apnea with increased Alzheimer's disease biomarker

A new study has highlighted a link between a health condition called sleep apnea and the accumulation of a brain biomarker associated with Alzheimer's disease. At the heart of the issue is tau, a protein that has been found in abundance in the brains of people with Alzheimer's disease. The new research has found a link between suffering from sleep apnea and tau accumulation, but questions remain.READ: Lack of deep sleep linked to build-up of Alzheimer's plaques

Sleep apnea is a health condition that causes a person to stop breathing periodically while asleep. Different forms of the condition exist, the most common one being obstructive sleep apnea with about 3 million diagnosed cases every year in the US.

The relationship between sleep and the development of Alzheimer's disease is a growing one, but scientists haven't yet worked out how it all fits together. The latest research looked at 288 participants who were at least 65 years old — and, notably, who did not have any cognitive impairment.

Each participant's partner was asked whether the volunteer had been witnessed experiencing sleep apnea episodes while asleep. As well, each participant underwent a PET brain scan to asses how many tau protein tangles had accumulated in the entorhinal cortex region of the brain, which is responsible for memory, time perception, and navigation.

The team found that participants with sleep apnea had 4.5-percent higher tau levels in this brain region, on average, than participants without sleep apnea. This was after controlling for other factors that may have influenced the levels, such as other sleep problems.

The study is described as preliminary at this time, and it raises a new question: does an increase in tau accumulation predispose someone to developing sleep apnea, or is sleep apnea a factor that may increase accumulation rates? Additional studies with larger sample sizes will been necessary to shed new light on the matter.

The research comes only days after a recently published study that found a link between lack of deep sleep and increased levels of these biomarkers associated with Alzheimer's disease. In that study, researchers found that deep sleep was an important factor in the glymphatic system, which essentially 'washes' the brain of these toxic proteins. Sleep apnea is known to interfere with deep sleep, but it's unclear whether that may play a role in the tau accumulation.