Melbourne School of Psychological Sciences - Theses
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ItemPredicting and improving the use of CPAP therapy in individuals with obstructive sleep apnoea( 2023-02)Obstructive sleep apnoea (OSA) is a common chronic sleep disorder characterised by the repetitive narrowing or collapse of the upper airway during sleep. Consequences of untreated OSA include fragmented sleep, intermittent hypoxia, memory deficits, increased risk of cardiovascular events and workplace accidents, and changes in mood, particularly depression. Comorbid depression is highly prevalent in OSA samples, and it is difficult to diagnose one condition in the presence of the other due to symptom overlap. Continuous positive airway pressure (CPAP) is the treatment of choice for moderate to severe OSA. However, CPAP use is suboptimal in many individuals. As such, there remains a significant burden of OSA on the individual and the healthcare system. The work presented in this thesis was part of a larger randomised controlled trial, the CPAP for OSA and Depression (COSAD) trial. The three experimental studies reported herein (Chapters 3-5) stemmed from the COSAD study design. Patients recently diagnosed with OSA and referred to the Austin Health sleep laboratory for CPAP implementation were recruited for this trial. Study 1 examined predictors of CPAP use up to 4 months post CPAP initiation. Predictors included patient and disease characteristics, sex, age, BMI, OSA severity, psychological variables (anxiety and depression), behaviour change variables (decisional balance and processes of change, and self-efficacy, which is comprised of 3 constructs; risk perception, outcome expectancies and CPAP self-efficacy), the first week of CPAP use, and wait time to CPAP initiation. A delay of 95 days to CPAP initiation was not associated with any differences in CPAP use at 1 week, 1 month and 4 months. Female sex, processes of change and self-efficacy were associated with CPAP use at 1 week. Average nightly CPAP use at 1 week was associated with CPAP use at 1 month and 4 months. No other patient or disease characteristics or psychological variables were associated with CPAP use up to 4 months. Study 2 investigated the effect of treating OSA with CPAP therapy on mood and sleepiness. Mood, including depression, anxiety and stress, were measured at baseline and 4 months and were compared between an intervention group (participants underwent 4 months of CPAP therapy for OSA) and a waitlist control group (participants were not treated for OSA). Stress improved in females with 4 months of CPAP therapy compared to females in the control group. Sleepiness, but not mood, improved after 4 months of CPAP therapy compared to control. Study 3 investigated the effect of a multi-dimensional intervention on CPAP use and self-efficacy compared to treatment as usual. CPAP use and self-efficacy improved in the intervention group compared to treatment as usual across the 4-month trial. These findings support previous work that early CPAP use predicts subsequent CPAP use, that CPAP use improves daytime sleepiness and that an intervention can increase CPAP use. Furthermore, this work has advanced the field by demonstrating that a delay to CPAP initiation may not effect subsequent CPAP use. Additionally, there may be sex differences in stress symptoms when treating OSA with CPAP therapy. Implications for future studies include the importance of the early period of CPAP use and the effect of wait time to therapy initiation on subsequent CPAP use.