March 25, 2019&mdash;Could having sleep apnea raise a person's risk for the type of brain changes often seen in Alzheimer's disease? Or could it be the other way around? Scientists don't know yet. But a preliminary study is now raising both of these intriguing questions. 

It found that people who likely have sleep apnea often have higher levels of a protein called tau in the brain. In people with Alzheimer's, tau forms abnormal tangles inside nerve cells&mdash;a hallmark of the disease. Previous research has tied sleep apnea to an increased risk of dementia, a decline in memory, thinking and other cognitive skills. In the current study, researchers wanted to know if tau deposits might be involved.

The study involved seniors who did not have dementia. Their bed partners were asked whether they noticed them stop breathing during sleep, which is a sign of sleep apnea. Researchers also used brain scans to look for tau buildups. 

The researchers found that 15 percent of the study group&mdash;or 43 participants&mdash;had bed partners who said they stopped breathing during sleep. Compared to the rest of the study participants, these people had more tau in a part of the brain that aids memory. 

 'A chicken and egg problem' 

More studies are needed to confirm the findings and to help answer what one of the researchers called a "chicken and egg problem." In other words: Does sleep apnea cause tau deposits? Or does tau accumulation lead to sleep apnea? According to the research team, the findings at least suggest that either of these scenarios may be a possibility. 

The study's researchers will present their findings at the <a target="_blank" href="https://www.netreturns.biz/healthinfo/bouncelink.aspx?shortcut=neurology">American Academy of Neurology's</a> annual meeting. Among the study's limitations is the fact that the work is preliminary and relatively small, and none of the participants were actually diagnosed by a doctor with sleep apnea.

Sleep apnea, Alzheimer's may be linked

Scientists say it's a 'chicken and egg' question.