Inclusion Criteria:  Newly diagnosed moderate-severe OSA (by standard criteria) Absence of known hypertension and antihypertensive medication Office blood pressure <140/90mmHg Age 18 - 70 years Able to provide written, informed consent  Exclusion Criteria:  Pregnancy Previous diagnosis of OSA or previous CPAP treatment Diagnosis of Diabetes Mellitus Active treatment for malignancy or severe psychiatric disorder History of cardiovascular disease or cerebrovascular disease Moderate or severe chronic kidney disease (CKD) defined as a eGFR of ≤ 44mL/min/1.73m2 Dipper on ABPM Morbid obesity, defined as BMI ≥40 Professional drivers or drivers with a history of road-traffic accident due to sleepiness Severe excessive daytime sleepiness defined as Epworth sleepiness scale (ESS) >15