Side effects to continuous positive airway pressure treatment for obstructive sleep apnoea: changes over time and...

Continuous positive airway pressure (CPAP) is an effective treatment against obstructive sleep apnoea, but adherence is often low, and side effects are common. It is unclear from previous research whether side effects are significant causes of nonadherence. No study has examined if side effects vary within subjects over time. The aims were to (1) examine the evolution of CPAP side effects over time, and (2) prospectively assess correlations between early CPAP side effects and treatment adherence.

One hundred eighty-six obstructive sleep apnoea patients from three sleep centres were prospectively enrolled. They completed the Side Effects to CPAP Inventory, where the respondent rates the frequency, magnitude and perceived impact on adherence from 15 side effects. Adherence was measured by treatment dropout and machine usage time.

The most common side effects were dry mouth, increased number of awakenings, blocked up nose, mask pressure and mask leaks. While some side effects were stable over time, others could both resolve and emerge within subjects. Dry mouth, mask leakage and blocked up nose emerged within 1 year in approximately 30% of patients who had not experienced them after 2 weeks. Increased number of awakenings and dry mouth after 1-2 weeks were significantly associated to treatment dropout during the first year and machine usage time after 6 months.

While some side effects are related to adherence, most are not. Not all side effects are stable over time. This, together with differences in methodology between studies, might explain the conflicting findings in earlier research.