Psychological Predictors of Adherence to Treatment in Obstructive Sleep Apnea Patients

Abstract

Obstructive sleep apnea (OSA) is a condition where the patient’s airway collapses during sleep, causing lack of oxygen and consequent arousal from sleep. Consequences of the disease include excessive daytime sleepiness, impaired quality of life, hypertension, cardiovascular disease and metabolic syndrome. Continuous positive airway pressure (CPAP) is considered the gold-standard treatment for OSA. However adherence to CPAP treatment is poor, with sleep disorders having one of the lowest rates of adherence in chronic diseases. Many attempts have been made to try to identify those patients who are at risk of non-adherence. Baseline variables such as body mass index, treatment pressure, age, and gender have not been found to be predictive of future CPAP adherence. However some promise has been shown in psychological theories such as social cognitive theory (in particular self-efficacy), transtheoretical modelling and Health Belief Models. In other chronic diseases the self-regulatory model (illness representations and beliefs about medicines), social support, the theory of planned behaviour (intentions) and social cognitive theory (self-efficacy) have shown promise in being able to predict subsequent patient adherence. These theories were combined to create the patient perceptions questionnaire (PPQ). This primary aim of this study was to test the ability of the PPQ, when delivered at baseline, to predict patient adherence to CPAP at 90-days. The study also aimed to assess changes in PPQ answers over time, assess relationships between the PPQ and adherence at other time-points and to assess subjective adherence and side-effects. A prospective longitudinal study design was employed. A total of 217 patients newly diagnosed with OSA were recruited by Clayton Sleep Institute in St Louis, Missouri, USA. Eleven patients were withdrawn and 39 were lost to follow-up because they did not complete the primary endpoint of an objective adherence measurement at 90-days. The final analysis included 167 patients who completed questionnaires at baseline, followed by questionnaires and objective adherence measurements at 14, 60 and 90-days. The demographic variables that were consistently associated with adherence were race, income and marriage status. When administered at baseline the PPQ items of higher perceived treatment control, perceived partner support and attitude, self-efficacy and intention to adhere as well as lower concerns about treatment were associated with both 14 and 90-day adherence. When combined in a regression model, demographic and questionnaire variables were able to explain 19.9 and 18.4% of the variance in CPAP adherence at 14 and 90-days respectively. The PPQ items of illness timeline and coherence and self-efficacy increased over time. Objective adherence decreased over time, and was on average over-reported by patients by 42 minutes. Patient reported side-effects significantly increased over time and were associated with 60 and 90-day adherence. This study shows ability of the PPQ to predict CPAP adherence in OSA patients. Future studies should consider these health psychology theories (i.e., illness perceptions, beliefs about treatment, self-efficacy, intentions and social support) when designing interventions to improve CPAP adherence.