Sleep-related breathing disorders and risk of stroke

Background - Stroke and sleep-related breathing disorders are both common a nd 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 wil l outline the scientific basis for this relationship and suggest sleep-rela ted breathing disorders as modifiable risk factors for stroke. Summary of Review - Several studies have shown a characteristic circadian r hythmicity in stroke. We have discussed the influence of normal sleep state s as well as the effect of sleep-related breathing disorders on cerebral he modynamics. The hemodynamic, metabolic, and hematologic changes during slee p-related breathing disorders in the form of decreased cerebral perfusion a nd increased coagulability are possible pathogenetic mechanisms for stroke. There are accumulating lines of evidence that sleep apnea disorder may ind eed cause diurnal hypertension. However, the increased risk of stroke in pa tients with sleep-related breathing disorders appears to be independent of coexisting hypertension; the presence of hypertension would increase the ri sk even further. Furthermore, several studies have documented high prevalen ce of sleep apnea disorders in patients with transient ischemic attacks and stroke. Conclusions - Sleep-related breathing disorder appears to contribute as a r isk 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 t hese disorders.