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Untreated obstructive sleep apnea is linked to many medical conditions including stroke, heart disease and diabetes. Sleep apnea is also linked to many cognitive impairments, including poor mood, memory and mental task deficits.
One of the most common questions I field from patients when discussing sleep apnea is the mechanism by which OSA could lead to these seemingly disparate medical conditions. After all, how could sleep apnea lead to both heart disease and poor memory?
An interesting new article published in the journal Sleep may help answer that question.
The study authors took two groups of patients, one with severe obstructive sleep apnea and the other healthy controls, and performed sleep studies, specialized MRI brain scanning, and blood measurements looking at vascular endothelial (blood vessel lining) health. The authors’ goal was to examine the relationship between sleep apnea severity, brain white matter integrity and systemic inflammation (read vascular inflammation).
In the study, patients with the severe OSA were showed to have significantly impaired white matter integrity in variety of vulnerable brain regions, and the impairments were shown to be more pronounced the worse the sleep apnea severity. The white matter changes also were correlated to circulating inflammatory markers in the patients with sleep apnea
The “year after year decade after decade” pattern of repetitive nightly drops in oxygen are felt to be a primary culprit in this disease process. Increased endothelial oxidative stress, which is a type of inflammation in the lining of the blood vessel walls in our bodies, is triggered by these up-down fluctuations in oxygen.
Interestingly, similar paradigms of vascular oxidative stress are seen in many other disease pathways, including cholesterol and triglyceride mediated blood vessel inflammation- or in plain English, coronary heart disease. These data could partly help explain why poor diet and nutrition are associated with so many of the very same diseases linked to sleep apnea.
Circling back to sleep apnea and cognition, the impairments in brain white matter integrity seen with untreated severe sleep apnea could certainly help- at least in part- to explain declines in mood, memory and cognitive tasks seen in so many patients with OSA.
As always, if you have any questions about these topics you should discuss them with your physician.
Roy Artal, M.D.
For additional information on this and related topics please see the following resources:
Chen HL, et al. White matter damage and systemic inflammation in obstructive sleep apnea. Sleep. 2015;38:361-370.