Background There are very few data on objectively assessed long-term compliance with continuous positive airway pressure (CPAP). No single factor has been consistently identified as predictive of continued CPAP use.

Methods Adherence to and associations with objective CPAP use were examined in 639 of 3900 patients in whom CPAP treatment was started between 1994 and 2005. Kaplan–Meier survival analyses were used to estimate the proportion of patients still on CPAP. Cox regression models were used to explore the effects of covariates on continued use of CPAP.

Results The median (IQR) follow-up time after initiating CPAP therapy was 3.9 (1.5–6.9) years and the average use of CPAP was 6.2 (4.5–7.3) h/night. The percentage of patients adherent to CPAP after 5 and 10 years was 81% and 70%, respectively. Multivariate analysis, including gender, age, neck circumference, Epworth Sleepiness Score, oxygen desaturation index (ODI) and research study participation, indicated that ODI was the only clinical variable independently associated with long-term adherence to CPAP (HR per 1 event=0.97, p<0.001, 95% CI 0.96 to 0.98). ODI categories were significantly associated with the risk for stopping CPAP in multivariate analysis (using ODI group 0–15/h as reference, HR for ODI group >15–30/h=0.68, p=0.100, 95% CI 0.43 to 1.08; for ODI group >30–60/h=0.37, p<0.001, 95% CI 0.22 to 0.60; and for ODI group >60/h=0.17, p=0.001, 95% CI 0.06 to 0.48).

Conclusions The majority of patients with sleep-disordered breathing are using CPAP in the long term and the severity of sleep-disordered breathing rather than sleepiness determines long-term adherence to CPAP therapy.