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.