ARTICLE IN BRIEF
New data suggest that brainstem infarction may contribute to post-stroke sleep apnea.
SAN DIEGO—Patients diagnosed with strokes involving the brainstem are highly likely to have sleep apnea, researchers reported here at the annual International Stroke Conference sponsored by the American Stroke Association and the American Heart Association.
In the unadjusted model, 84 percent of the patients with a brainstem infarct experienced sleep apnea, with a median apnea-hypopnea index (AHI) of 20, Devin Brown, MD, associate professor of neurology and director of the Vascular Neurology Residency Program at the University of Michigan in Ann Arbor, reported. [Sleep apnea was defined at as an AHI of 10 or greater. The index is the sum of the apneas and hypopneas per hour.]
About 59 percent of patients without a brainstem infarct experienced sleep apnea with a median AHI of 13, she said. The odds ratio of having sleep apnea if a person had a brainstem infarct was 3.71 (p=0.004).
“This did not attenuate at all when adjusted for confounders,” Dr. Brown said. The adjusted model — correcting for age, sex, race/ethnicity, body mass index, hypertension, diabetes, coronary artery disease, prior stroke, and National Institutes of Health Stroke Scale — showed basically the same results, with an odds ratio of 3.76, and a p-value of 0.004.
“The presence and severity of sleep apnea are associated with the brainstem location of acute infarction,” Dr. Brown said in her oral presentation. “Brainstem infarction may be a contributor to some post-stroke sleep apnea.”
She said the role of sleep apnea in stroke is important because people diagnosed with sleep apnea are at high risk of stroke. “It predicts poor stroke outcome and is very common after stroke.” However, researchers are not sure if sleep apnea causes brainstem-located stroke or if brainstem strokes cause sleep apnea.
Dr. Brown and researchers went after part of the chicken-and-egg question, trying to determine if having a brainstem stroke is related to sleep apnea during follow-up. “Because dysphagia is associated with sleep apnea and because brainstem injury is related to breathing difficulty, we hypothesized that brainstem infarction is associated with the presence and severity of sleep apnea in post stroke patients,” she said.
To perform the study, researchers accessed records from the BASIC Study (Brain Attack Surveillance in Corpus Christi Project), an ongoing stroke surveillance study in Nueces County, TX. All cases of stroke were identified at hospitals in the county, and study neurologists validated each stroke case.
Dr. Brown explained that sleep apnea assessments were made within 30 days of the stroke using ApneaLink Plus devices, which included validated portable cardiorespiratory monitoring. A registered polysomnographic technologist edited the raw data.
The researchers abstracted medical information from BASIC and determined the area of infarct, and whether the infarct was in the brainstem. Through logistic and linear regression models the researchers determined associations between brainstem involvement and sleep apnea or AHI, using unadjusted and adjusted models.
The study included 355 subjects. The median time from stroke symptoms onset to sleep apnea assessment was 13 days. About 91 percent of the participants underwent magnetic resonance imaging of the brain. The other patients were evaluated with computer-assisted tomography (CT) scans. Brainstem infarction was diagnosed in 38 patients — 11 percent of the cohort. [See “More About the Study Participants.”]
“We did not exclude patients who had a history of sleep apnea,” Dr. Brown said in response to questions from session moderator Maria Aguilar, MD, associate professor of neurology at the Mayo Clinic in Phoenix, AZ. “We don't know if these patients got worse after their stroke,” Dr. Brown said.
She said the trial might be limited because it did not perform laboratory-based polysomnography, the gold standard for sleep apnea evaluation. She also said that the determination of brainstem location was based on a retrospective review of reports rather than re-review of imaging.
On the other hand, she noted that her work represented the largest study that has ever addressed the question of whether the brainstem location and sleep apnea are linked. The study was a population-based sample and represented a bi-ethnic community.
In response to questions from the audience, Dr. Brown said that the researchers did not determine in which part of the brainstem the infarct occurred. Due to the fact that the researchers were using reports rather than imaging, Dr. Brown said that a relationship between infarct size and sleep apnea or sleep apnea severity could not be determined.
She said that some studies in Europe have suggested that during follow-up sleep apnea does improve, although it continues to persist.
Dr. Brown's study was sponsored by a grant from the National Institutes of Health, primarily by the National Heart, Lung and Blood Institute.
Commenting on the study, Daniel Lackland, PhD, professor of epidemiology at the Medical University of South Carolina in Charleston, told Neurology Today: “It has been suspected for some time that there is this relationship between sleep apnea and the brainstem. What is interesting in this study is that the researchers have been able to show that the severity or the sleep apnea is also related to brainstem infarcts.”
He suggested that the study indicates a “dose” effect of sleep apnea and brainstem infarcts. “We know that we can successfully treat sleep apnea, which occurs in people who are obese and in people who are not obese. That treatment technology is improving and getting much, much better.”
Dr. Lackland noted that sleep apnea is associated with high blood pressure, with stroke, and with heart attack along with other conditions. He said the findings of an association with brainstem infarct are another reason to focus on treating the disorder.
MORE ABOUT THE STUDY PARTICIPANTS
* The median age of those with brainstem infarctions was 60; the median age for patients who did not have a brainstem infarction was 66 (p<0.05).
* Of those with brainstem infarction, 74 percent or 28 patients were Mexican-American; those without a brainstem infarct were 57 percent Mexican-American, but that was not statistically different.
* About 55 percent of both groups were men; more than 80 percent had hypertension; 63 percent of those with brainstem infarcts were diabetic compared with 45 percent of those without brainstem infarcts (p<0.05).
* About 25 percent of patients in both groups had a history of stroke or transient ischemic attacks.
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