BACKGROUND:

Recent research has shown that sleep disordered breathing (SDB) is much more common than previously thought. While it is known that in clinic samples, SDB is associated with hypertension, cardiovascular disease and mortality, little is known about the natural history of this disorder, particularly in the general population, nor about the causal role of known risk factors. The knowledge obtained from the results of this study will help advance the field of sleep disorders medicine. Information about longitudinal effects and causal relationships may be applied to clinical situations, thus reducing the morbidity and mortality associated with this disorder. The study of the Hmong is the first attempt at characterizing SDB in a population never studied, but at potentially high risk for unknown death during sleep. If successful, that is if the Hmong adults are in fact at higher risk for SDB, this would not only help in preventing early death in this group, but also help in the understanding of the pathophysiology of this disorder.

DESIGN NARRATIVE:

In this longitudinal study, follow-up polysomnography and other protocols are conducted on an established cohort of men and women, ages 35-70, currently enrolled in the Wisconsin Sleep Cohort Study. The proposed follow-up studies will yield data spanning 5-15 years, with two to five data collection points. In addition, home polysomnography protocols will be conducted on Hmong adults. The study aims to : 1) describe with optimal parameters the natural history and biologic spectrum of SDB; 2) test the role of obesity and other risk factors in the occurrence and progression of SDB; 3) test the hypothesis that SDB has a causal role in the development and exacerbation of elevated blood pressure and other cardiovascular disease risk factors; 4) test the hypothesis that SDB causes behavioral morbidity, including extreme daytime sleepiness, cognitive impairment, motor vehicle accidents, and depression; 5) characterize SDB and other sleep disorders in Hmong, a minority population at high risk for sudden death during sleep.

Follow-up of the cohort continues through March, 2009 to investigate the role of SDB as a determinant and correlate of preclinical cardiovascular and cerebrovascular disease (CVD/stroke), incident CVD/stroke, mortality and in chronic daytime dysfunction. Changes in SDB occurrence and its effects with aging from middle to older age will also be investigated. To achieve these goals follow-up exams will conduct the following tests for preclinical CVD/stroke: 24 hour ambulatory blood pressure, ankle-brachial systolic blood pressure index, carotid intima-media thickness, exercise treadmill test, and ECG. Polysomnography will also be performed, in addition to the follow-up exams, on a subsample of 500 men and women who will transition from middle to older age (>60 years) .