Should use of 4 hours continuous positive airway pressure per night be considered acceptable compliance?

Continuous positive airway pressure (CPAP) reduces blood pressure in obstructive sleep apnoea (OSA) patients, as well as in patients with resistant hypertension. The effect of CPAP is directly related to treatment compliance [1–3]. Observational studies have shown a reduction in cardiovascular mortality risk in severe OSA patients treated with CPAP and adequate compliance [4–6]. A recent randomised controlled trial (RCT) showed a reduction in cardiovascular events (including hypertension incidence) in patients with adequate CPAP compliance [7]. However, what is an adequate definition of CPAP compliance? Ideally, CPAP compliance should take place for as long as the patient is sleeping but, in practice, this occurs in a minority of subjects. Based on several studies, compliance of ≥4 h per night has been considered acceptable. However, dose–response studies have found that different compliance levels achieve different dimensions of clinical improvement [8–11]. For instance, in order …