Sleep-related breathing disorders and risk of stroke.

BACKGROUND Stroke and sleep-related breathing disorders are both common and are associated with significant morbidity and mortality. Several recent large epidemiological studies have shown a strong association between these 2 disorders independent of known risk factors for stroke. This article will outline the scientific basis for this relationship and suggest sleep-related breathing disorders as modifiable risk factors for stroke. SUMMARY OF REVIEW Several studies have shown a characteristic circadian rhythmicity in stroke. We have discussed the influence of normal sleep states as well as the effect of sleep-related breathing disorders on cerebral hemodynamics. The hemodynamic, metabolic, and hematologic changes during sleep-related breathing disorders in the form of decreased cerebral perfusion and increased coagulability are possible pathogenetic mechanisms for stroke. There are accumulating lines of evidence that sleep apnea disorder may indeed cause diurnal hypertension. However, the increased risk of stroke in patients with sleep-related breathing disorders appears to be independent of coexisting hypertension; the presence of hypertension would increase the risk even further. Furthermore, several studies have documented high prevalence of sleep apnea disorders in patients with transient ischemic attacks and stroke. CONCLUSIONS Sleep-related breathing disorder appears to contribute as a risk factor for stroke through hemodynamic and hematologic changes. Because of the high prevalence of sleep apnea disorder in this population, patients with transient ischemic attacks and stroke should undergo evaluation for these disorders.