Obstructive sleep apnea syndrome (OSAS) is a common disorder with prevalence rates of at least 4% among the middle-aged male Caucasians and Hong Kong (HK) Chinese populations. It is characterized by repetitive episodes of upper airway obstruction, causing intermittent hypoxia, sleep fragmentation, disabling daytime sleepiness, impaired cognitive function and poor health status. OSAS patients are at increased risks of non-fatal and fatal cardiovascular morbidity and mortality including sudden death, in addition to being more prone to road traffic accidents. However, there is no long term follow up of patients with OSAS on the incidence of cardiovascular disease, compliance on the therapy and the impact of the quality of life. The study is aimed to carry out a prospective observational study assessing the role of OSAS as a possible cause of increased cardiovascular risk and cognitive decline.

Inclusion Criteria:

• suspected obstructive sleep apnea syndrome
• aged 18 or above
• must be able to speak, read and understand Chinese or English
• possess the ability to respond to questions and follow instructions.

Exclusion Criteria:

• already treated sleep apnea,
• a limited life expectancy due to illness unrelated to sleep apnea
• human immunodeficiency virus (HIV),
• advanced renal disease,
• uncontrolled malignancies
• documented alcohol or drug abuse up to 1 year prior to inclusion in the study.

Consecutive patients are recruited from the Respiratory Clinic at the Prince of Wales Hospital with clinical suspicion of sleep-disordered breathing. The Respiratory Clinic receives referral from hospital specialists and general practitioners. The clinical evaluation procedure includes an interview by a respiratory specialist followed by either an inpatient polysomnography or home polygraphic study according to the patients' clinical characteristics and preference in concordance of the guidelines from the American Academy of Sleep Medicine (AASM). Sleep records will be scored based on standardized criteria of AASM.