Subjects referred to a sleep clinic had polysomnography (PSG), clinic BP measurements, 24-hour ABP monitoring and HBP monitoring using a device (Microlife WatchBP HomeN) that allows daytime (3 days, 2 duplicate readings/day) and automated nighttime BP measurement (3 nights, 3 readings/night).

Inclusion Criteria:

• Age ≤ 65 years
• Suspected OSA
• Treated or untreated for hypertension

Exclusion Criteria:

• History of cardiovascular disease (heart failure, coronary heart disease, arrhythmia or stroke)
• History of asthma or chronic obstructive pulmonary disease (FEV1/FVC <70%)
• History of diabetes mellitus, collagen diseases and sarcoidosis
• Serum creatinine >1.6 mg/dl, proteinuria
• Previous treatment with CPAP
• Pregnancy or menstruation during the study
• Treatment with steroids, lithium or any other drugs affecting BP
• Change in antihypertensive treatment(if any) in the last 8 weeks before study entry

Subjects referred to a sleep clinic