Sleep-disordered breathing defined by an apnea–hypopnea index (AHI) of greater than five events per hour is a prevalent disorder estimated to affect 9–24% of middle-aged adults [15]. Obstructive sleep apnea syndrome (OSAS) with both abnormal sleep-disordered breathing and excessive daytime somnolence affects 2–4% of adults. OSAS is strongly associated with significant medical and social morbidity, including increased risk of hypertension, decreased functional quality of life and performance, and increased frequency of accidents [6]. Most risks are elevated with moderate or severe OSAS. However, morbidity and symptoms of OSAS occur with milder forms of the disease and risks are associated with an AHI at both the mild and the severe end of disease spectrum without threshold effects.