Studies have shown that people with obstructive sleep apnea have approximately double the risk of having a stroke as people without sleep apnea. How exactly does sleep apnea increase the risk of stroke?
The relationship between sleep apnea and stroke is likely due to several factors, and the exact mechanism is not fully understood. However, there are several theories.
Changes in blood flow during apneas may affect the risk for stroke. Studies show that blood flow within the arteries of the brain decreases during apnea, and this correlates with the duration of the apneic event.
Another possibility is that strokes are more common because sleep apnea exacerbates known risk factors for stroke, including high blood pressure, diabetes, and heart disease.
Sleep apnea also causes inflammation in the body by promoting the release of stress hormones during periods of apnea. This ultimately causes changes in blood vessels and clotting, which may make strokes more likely.
Finally, the risk factors for sleep apnea and stroke (such as obesity) may be shared.
Netzer, N, et al. "Blood flow of the middle cerebral artery with sleep-disordered breathing: correlation with obstructive hypopneas." Stroke, 1998; 29:87.
Valham, F, et al. "Increased risk of stroke in patients with coronary artery disease and sleep apnea: a 10-year follow-up." Circulation, 2008; 118:955.
Yaggi, HK, et al. "Obstructive sleep apnea as a risk factor for stroke and death." N Engl J Med, 2005; 353:2034.