Health belief model predicts adherence to CPAP before experience with CPAP

Adherence to continuous positive airway pressure (CPAP) therapy for obstructive sleep apnoea (OSA) is often poor. Biomedical indices explain little of the variance in CPAP use. The present study tested a health belief model of adherence in order to determine the contribution of psychological constructs as compared to biomedical indices in the prediction of CPAP adherence. Consecutive patients (n = 77) newly diagnosed with OSA and naïve to CPAP treatment (had never tried CPAP before) completed questionnaires at baseline (prior to CPAP treatment). The questionnaires assessed: outcome expectancy with treatment, self-efficacy, functional outcomes of sleepiness, and perceived risk of negative health outcomes. Physiological data were obtained from a standard clinical diagnostic sleep study. CPAP adherence was assessed at 4-month follow-up. Health belief model constructs alone explained 21.8% of the variance in CPAP adherence, whereas health belief model constructs and biomedical indices together explained 31.8% of the variance in CPAP adherence. The greatest proportion of CPAP adherence was explained by higher outcome expectancies with treatment, greater functional limitations as a result of sleepiness and lower risk perception. The results suggest that patients have developed beliefs and expectations about obstructive sleep apnoea and continuous positive airway pressure even before they try continuous positive airway pressure treatment. These beliefs and expectations predict the patients' adherence to effective therapy.