Sleep Apnea May Increase Alzheimer's Risk for Those Genetically Predisposed

According to the research published in Annals of the American Thoracic Society, people who already have had Alzheimer's in their family are at-risk of having the disease themselves when they have sleep-disordered breathing. 

In a study called, "Greater Cognitive Deficits with Sleep-Disordered Breathing among Individuals with Genetic Susceptibility to Alzheimer's Disease: The Multi-Ethnic Study of Atherosclerosis," the researchers who participated reported that the participants who were found to carry the apolipoprotein ε-4 (APOE-ε4) allele have greater cognitive deficits with the various amounts of sleep-disordered breathing compared to those that are found not to have the allele at all.

What is the apolipoprotein ε4?

Usually shortened to APOE, the apolipoprotein ε4 is a major cholesterol carrier that supports injury repair in the brain. According to what has been found in other studies, people who carry the alternate form of the gene, ε4 allele, have the greatest level of risk of containing Alzheimer’s disease. It is estimated that at least 20 percent of the population actually carries this gene.

According to the study author, Dayna A. Johnson, PhD, MPH, MS, MSW, instructor of medicine at Harvard Medical School and the Brigham and Women's Hospital, previous studies have shown very inconsistent findings regarding sleep-disordered breathing and cognition, however, the doctor has also mentioned this inconsistency must be caused due to different tests used.

The team of researchers led by Dr. Johnson evaluated the association between sleep apnea and Alzheimer’s disease by using diverse samples and different indicators of how this breathing disorder may accelerate neurodegenerative conditions. Actually, these particles, the APOE-ε4 allele were found to be extremely influential for the link between sleep-disordered breathing and cognition.

The study and the findings it provided

The study authors analyzed more than 1,700 participants in order to collect the data they needed. There was a total of 1,752 participants, all around 68 years old. The study took place in the Multi-Ethnic Study of Atherosclerosis (MESA). These participants underwent an in-home polysomnography (sleep) study and then completed standardized sleep questions, and a battery of tests to measure their cognition. The researchers defined sleep-disordered breathing as an apnea-hypopnea index (AHI), an index that is able to measure the number of times breathing stopped while the participant is sleeping, but it also measures shallow breathing.

During this study it was found that:

• Participants feeling sleepy throughout the day resulted in having a slower cognitive processing speed.
• Most of them were found to have increased overnight hypoxemia which is an oxygen saturation below 90%, another factor that contributed in participants having poorer attention and a more limited memory span.
• All these associations were found to be stronger among APOE-ε4 carriers.

Read on to learn more about this study that uncovered this increased risk factor for some sleep apnea patients.