Background <p>Obstructive sleep apnoea (OSA) is a chronic condition characterised by recurrent episodes of apnoea and hypopnoea. People with untreated OSA are at increased risk of excessive daytime sleepiness (EDS), functional impairment and developing cardiovascular conditions, metabolic and neurocognitive diseases. EDS is a key determinant of quality of life (QoL) and is associated with increased healthcare utilisation and accident risk. Untreated OSA can also lead to impaired work productivity, reduced health-related quality of life (HRQoL) and life expectancy, which contribute to the UK economic burden.</p> Aim <p>To review and critically appraise all published economic evaluations that assessed the cost-effectiveness of devices and strategies to diagnose and manage people with moderate-to-severe OSA.</p> Methods <p>This systematic review was conducted following the Preferred Reporting Items for Systematic Reviews guidelines and registered in the Prospective Register of Ongoing Systematic Reviews (CRD42024535732). We searched electronic databases up to March 2025. Two reviewers undertook screening, data extraction and quality appraisal using recognised reporting quality and methodological quality appraisal tools. The findings were summarised and discussed narratively.</p> Results <p>Twenty-nine studies were included. Fifteen studies included an economic evaluation alongside a clinical trial and 14 studies were model-based economic analyses. Although many analyses were methodologically sound in their overall approach, there were concerns regarding choice of time horizon, selection of health states, undertaking pre-model analyses and long-term adherence and efficacy of continuous positive airway pressure treatment (CPAP). Substantial methodological heterogeneity was identified across studies, including variation in diagnostic thresholds and scoring criteria used, model structures and assumptions regarding treatment adherence. Only four of twenty-nine included studies used home respiratory polygraphy (HRP) as a comparator, limiting the direct applicability of much of the evidence to the UK setting.</p> Conclusion <p>Past economic analyses offer insight into the methods used to assess the cost-effectiveness of strategies to diagnose OSA. These economic analyses are a useful framework to build on, but clear gaps exist in the clinical and economic evidence. Future economic evaluations should prioritise contemporary diagnostic pathways and technologies, use consistent diagnostic definitions, and incorporate more realistic modelling of long-term treatment adherence and benefit. Until such information becomes available, the true cost-effectiveness of these strategies remains unknown.</p>