The aim of this thesis was to explore the impact of the common sleep-related breathing disorder, obstructive sleep apnoea (OSA); specifically for people with a bipolar disorder (BD) diagnosis but also the wider experience of the first-line treatment for OSA, positive airway pressure (PAP).

Chapter 1 is a systematic literature review and thematic synthesis of experiences
using PAP to treat OSA. Twenty-five papers were reviewed and included in the thematic synthesis. The quality of each paper was appraised and considered in relation to contribution to the resultant analytical themes. The metasynthesis gave voice to user experiences of PAP and revealed barriers to PAP use at a healthcare service level. The findings highlight the need for a biopsychosocial approach and long-term person-centred support to enhance PAP use.

Chapter 2 is a primary empirical research paper on an investigation as to whether people with suspected-OSA and a BD diagnosis experience more sleep and affect instability when “inter-episode” compared to people with a BD diagnosis alone. Ecological momentary assessment was utilised. Eighteen participants (twelve with suspected-OSA) wore an acitgraph for two weeks whilst completing an affect questionnaire twice daily. Measures of instability were calculated using the mean squared successive difference and probability of
acute change indices. The groups were not found to significantly differ other than reduced sleep efficiency in the suspected-OSA group. However, only 48% of the intended sample was successfully recruited due to the COVID-19 pandemic. Important avenues for further research are highlighted.

Chapter 3 is a critical appraisal of the thesis. Salient issues relevant to future research and clinical practice are discussed, in addition to the under recognised clinical issue of sleep which inspired this thesis.