The patients' medical records will also be reviewed for compliance to treatment for SDB, and the patients will be classified as treated or untreated. The treated group will be divided into two subgroups: those with "good adherence" to PAP therapy (≥ 4 hours PAP use per night) and those with "poor adherence" to PAP therapy (< 4 hours PAP use per night). Healthcare Utilizations, HF or COPD exacerbations and mortality will be identified by reviewing medical records, National database when available, or self-reported by patient or patient's family through phone interview or questionnaire.