People who carry a genetic susceptibility to Alzheimer’s disease may be at greater risk of diminished cognition from sleep-disordered breathing than people without the susceptibility, according to new research published in the Annals of the American Thoracic Society.
The findings show that study participants who carry the apolipoprotein ε-4 (APOE-ε4) allele exhibit greater cognitive deficits due to sleep-disordered breathing compared to people without the allele.
APOE is a major cholesterol carrier that helps repair injuries in the brain. Previous research has shown that those carrying the alternate form of the gene, ε4 allele, are at increased risk of Alzheimer’s disease. It is estimated that about 20 percent of the population carries this allele.
For the study, the researchers analyzed data from 1,752 participants (average age 68) in the Multi-Ethnic Study of Atherosclerosis (MESA). The participants underwent an in-home sleep study, completed standardized sleep questions and a battery of tests to measure their cognition.
The research team looked for whether the presence of the APOE-ε4 allele — which is known to increase risk of Alzheimer’s disease — influenced the link between sleep-disordered breathing and cognition.
The authors defined sleep-disordered breathing as an apnea-hypopnea index (AHI), which measures the number of stopped or shallow breaths per hour, and sleep apnea syndrome plus self-reported sleepiness (based on a standardized scale).
The researchers found the following:
- Increased overnight hypoxemia (oxygen saturation below 90 percent) or increased daytime sleepiness was linked with poorer attention and memory.
- Higher levels of daytime sleepiness were associated with slower cognitive processing speed.
- Sleep apnea syndrome was tied to poorer attention and processing speed.
- These associations were strongest in APOE-ε4 carriers.
The researchers adjusted for race, age, body mass index, education level, smoking status, hypertension, diabetes, benzodiazepine use, and depressive symptoms.
Lead study author Dayna A. Johnson, Ph.D., MPH, MS, MSW, instructor of medicine at Brigham and Women’s Hospital and Harvard Medical School noted that, overall, the effects of the various sleep factors they measured on cognition were small, and they were in the range previously reported for several other lifestyle and health risk factors for dementia.
Screening and treating sleep-disordered breathing, she added, may help reduce a person’s risk of dementia, especially if that individual carries APOE-ε4.
“Our study provides further evidence that sleep-disordered breathing negatively affects attention, processing speed, and memory, which are robust predictors of cognitive decline,” said senior study authors Susan Redline, M.D., MPH, and Peter C. Farrell Professor of Sleep Medicine, Harvard Medical School.
“Given the lack of effective treatment for Alzheimer’s disease, our results support the potential for sleep-disordered breathing screening and treatment as part of a strategy to reduce dementia risk.”
Source: American Thoracic Society