Researchers seek link between sleep apnea and stroke
July 25, 2012
CALGARY – Researchers with Alberta Health Services and the University of Calgary are trying to better understand why people with sleep apnea are at higher risk of stroke.
Some research suggests that sleep apnea, a disorder in which an individual intermittently stops breathing during sleep, increases the risk of stroke two to threefold.
“Our theory is that the lack of oxygen, or hypoxia, that people with sleep apnea experience during sleep impairs the usual defence mechanisms in the brain,” says Dr. Patrick Hanly, the principal investigator in the study and a member of the university’s Hotchkiss Brain Institute.
“The circulatory system in the brain regulates itself against stresses like high blood pressure and hypoxia itself, but sleep apnea may impair the effectiveness of that system and weaken the body’s natural defence against stroke.”
In the study, participants with sleep apnea will stay overnight in the sleep laboratory at Calgary’s Foothills Medical Centre during which their breathing and cardiovascular responses will be continuously monitored while they sleep.
The following day, they will spend time at Dr. Marc Poulin’s research laboratory at the U of C where their brain blood flow response to reduced oxygen levels will be assessed while they are awake. The same patients will then receive supplemental oxygen during sleep for two weeks, and will be tested again to see if the cerebral defense mechanisms have improved.
Researchers are also studying healthy subjects to confirm whether their cerebral defence mechanisms function better than in those with sleep apnea.
“If we can learn more about the physiological links between sleep apnea and stroke, we may be able to develop better prevention and treatment strategies,” Dr. Hanly says.
Gary Wellon, 34, can attest to the importance of expanding medical knowledge about sleep apnea. After a couple of close calls at the wheel when he was driving while drowsy, Wellon was diagnosed with a severe form of sleep apnea at the Foothills Sleep Centre in November 2011.
“The last time I almost came face to face with a semi; I don’t know how we didn’t trade paint,” says Wellon, who commutes to Calgary from Carseland, about 70 kilometres southeast of Calgary. “I knew there was something wrong with me but I didn’t know what.”
After an initial assessment, he was referred to the Foothills Sleep Centre, which is the main referral centre in southern Alberta that deals with the most complex sleep apnea cases.
Dr. Hanly placed Wellon on BiPAP (Bi-level Positive Airway Pressure), which is used to treat more severe cases of sleep apnea. He wore a mask during sleep connected to a pump that maintains a steady flow of air to keep the airway open and make breathing more efficient.
“After one night of that I woke up and felt like a million bucks,” Wellon says. “It used to be I would come home from work, eat dinner, sleep on the couch until 9 or 10, then go to bed. Now I have a lot more energy and come home and I do things, like play with my kids. It’s changed my life.”
It’s estimated as many as one in six people experience some form of sleep apnea. Aside from an increased risk of stroke, individuals with sleep apnea may be at greater risk of other cardiovascular disease such as high blood pressure and heart attack. It affects men more commonly than women, and is more prevalent among obese people. Anyone who suspects they may have sleep apnea should consult their family physician.
Researchers are still looking for healthy men and women who do not have sleep apnea between the ages of 18 and 60 to take part in the study. For more information on how you can get involved, phone 403-220-3390.
Dr. Patrick Hanly is Director of the Foothills Sleep Centre, Professor of Medicine, University of Calgary and a member of the Hotchkiss Brain Institute.
Dr. Marc Poulin is a Professor in the Faculties of Medicine and Kinesiology, a member of the Hotchkiss Brain Institute and the Libin Cardiovascular Institute of Alberta, and an Alberta Innovates – Health Solutions Senior Scholar.
Alberta Health Services is the provincial health authority responsible for planning and delivering health supports and services for more than 3.8 million adults and children living in Alberta. Its mission is to provide a patient-focused, quality health system that is accessible and sustainable for all Albertans.
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