People whose brainstems are affected by their stroke have a significantly higher prevalence of sleep apnea than those who have stroke-related injury elsewhere in the brain, according to research presented at the American Stroke Association’s International Stroke Conference 2014.

“This is the largest population-based study to address the issue of the location of the brain injury and its relationship to sleep apnea in post-stroke patients,” says Devin L. Brown, MD, MS, lead author of the study and associate professor of neurology and associate director of the stroke program at the University of Michigan in Ann Arbor, in a release.

The 355 ischemic stroke patients, average 65 years and 55% men, who participated in the study were drawn from those already enrolled in the Brain Attack Surveillance in Corpus Christi (BASIC) Project. Hispanics represented 59% of the study group; Non-Hispanic whites 35%; Native Americans 1%; and African-Americans 4%.

According to researchers, patients were also offered sleep apnea screening with a portable respiratory monitor and were screened about 13 days after a stroke.

Neurologists interpreted CT and MRI brain imaging scan results to determine if patients had brainstem involvement or no brainstem involvement.

Of the 11% of 355 stroke patients with brainstem injury, 84% had sleep apnea. Of those without brainstem involvement, 59% had sleep apnea.

“While these numbers are high, more research into the relationship between stroke and sleep apnea is needed before we recommend routine sleep apnea screening in post-stroke patients,” Brown says.

In the future, Brown says her group will continue to explore the relationship between sleep apnea and stroke.

Co-authors are Mollie McDermott, MD; Ashkan Mowia, MD; Ronald Chervin, MD, MS; Lewis Morgenstern, MD; Kevin Kerber, MD; Garnett Hegeman III, RPSGT; Melinda Smith, DrPH; Nelda Garcia, BS; and Lynda Lisabeth, PhD.