Determinants of nasal CPAP compliance

Abstract

Background: Obstructive sleep apnea is a prevalent condition with potentially serious medical and psychosocial consequences. Nasal continuous positive airway pressure (CPAP) is the treatment-of-choice and has been shown to reduce the frequency of nocturnal respiratory events, improve sleep architecture and decrease daytime sleepiness. Patient compliance with CPAP is disappointingly low. Previous studies examining determinants of CPAP compliance have limited the variables studied to patient (sociodemographic), disease status, and treatment variables, with few reliable determinants found.

Methods: The purpose of the current study was to investigate the relationship between objectively measured CPAP compliance and variables from social cognitive theory (SCT) and the transtheoretical model (TM). Scales that measure variables from each model were developed and reliability evaluated. The relationship between the SCT and TM variables and compliance at 1-month post-CPAP-fitting was prospectively evaluated on 51 first-time CPAP users. SCT and TM variables were measured on the day of CPAP-fitting, at 1-week post-CPAP-fitting, and at 1-month post-CPAP-fitting.

Results: SCT variables measured 1-week post-CPAP-fitting (R²=0.261, P=0.001) and TM variables measured 1-week post-CPAP-fitting (R²=0.17, P=0.002) accounted for a statistically significant amount of variance in objective CPAP compliance measured at 1 month. The decisional balance index (from TM) individually accounted for a significant amount of variance in objective CPAP compliance in the above analyses.

Conclusions: The ability of these new behavior change scales to predict CPAP compliance provides us with a new direction of research to better understand factors associated with compliance. The principal advantage of these theory-driven and empirically validated scales are that they measure modifiable factors that can provide the basis for sound interventions to improve CPAP compliance.

Introduction

Obstructive sleep apnea (OSA) is a disorder characterized by repeated cessations of breathing during sleep [1]. Consequences of OSA include excessive daytime sleepiness [2], altered sleep architecture [3], impaired neurocognitive performance [4], dysphoric mood [5], and significant psychosocial disruption [6]. Patients with OSA have increased morbidity from cardiovascular events [7] and automobile accidents [8]. Higher rates of mortality have been seen in middle-aged adults having more than 20 apneas per hour of sleep [9] or having a combination of snoring and excessive daytime sleepiness [10].

The treatment-of-choice for OSA is nasal continuous positive airway pressure (CPAP) [11]. CPAP has been shown to reduce daytime sleepiness [12], oxyhemoglobin desaturations [13], heart rate and pulmonary pressure [14], improve cognitive performance [15], and increase health-related quality of life [16]. Compliance with CPAP is associated with significant reductions in physician claims and hospital stays [17].

Despite the documented efficacy of CPAP, it is estimated that over 50% of those started on CPAP will not be using it 1 year later [18]. Of those using it 1 year later, most are not using CPAP for the entire night as prescribed. Published compliance rates in the United States range from 4.7 to 5.3 h per night [19], [20]. Rates outside the United States tend to be somewhat higher: 5.6 h per night in the United Kingdom [21], 5.6–6.5 in France [22], [23]. Because CPAP is accepted by only 50% of patients over a 1-year period and because those who do accept it are not using it as prescribed, it stands to reason that CPAP compliance could be significantly improved.

Determinants of CPAP compliance that have been studied can be classified into one of the three categories: patient/sociodemographic, disease-related, and CPAP-related. Few reliable determinants have been found [24], although improvement in sleepiness level appears to be associated with higher CPAP compliance [25]. Because CPAP is an aid and not a cure, significant behavior change on the part of the patient and the patient's family is necessary. Indeed, the sleep community is beginning to recognize the importance of the ‘human factor’ in CPAP compliance, e.g. the beliefs and behaviors of the patient and professional/patient interactions [26]. We decided to look at two contemporary, well-supported models of behavior change, social cognitive theory (SCT) and the transtheoretical model (TM), to better understand factors associated with CPAP compliance. Appendix A provides a description of these models. SCT hypothesizes that those patients with (a) higher perceived self-efficacy, (b) higher outcome expectancies for CPAP, (c) greater functional social support, and (d) greater knowledge will be more compliant with CPAP. The TM hypothesizes that those patients (a) with more pros than cons and (b) who use more processes of change will be more compliant with CPAP.

The purpose of this study was to investigate the relationship between objectively measured CPAP compliance and variables from SCT and TM. First, scales that measure variables from each model were developed and psychometric properties evaluated. Second, the ability of SCT and TM variables to predict compliance at 1-month post-CPAP-fitting was prospectively evaluated on 51 first-time CPAP users. It was hypothesized that SCT and TM variables measured: (a) on the day of CPAP-fitting would not be predictive of CPAP compliance and (b) at 1-week post-CPAP-fitting and at 1-month post-CPAP-fitting would be predictive of CPAP compliance.