In this study, participants with obstructive sleep apnoea (OSA) that start continuous positive airway pressure (CPAP) treatment will be asked to fill in questionnaires at baseline and two follow-up time points (3 and 6 months after the start of CPAP treatment). This information, information on CPAP adherence and information from the polysomnography assessment every participant has undergone prior to starting CPAP will allow us to investigate relevant outcomes of CPAP therapy in people with chronic pain. The detailed research questions are the following:
Primary research questions Longitudinal
1. Are average hours of CPAP use per night (continuous variable) associated with average pain intensity at 3-month follow-up in people with CP and OSA?
2. Is AHI at baseline associated with average pain intensity at 3-month follow-up in people with CP and OSA?
Secondary research questions Cross-sectional
1. Is there a difference in CPAP use in hours (measured at 3-month follow-up) between people with OSA-only, OSA and CP, OSA and comorbid insomnia (COMISA - defined via the Insomnia Severity Index ≥15) and COMISA with CP?
2. What is the prevalence of CP in patients with clinically relevant OSA in a sleep clinic setting?
3. Is there a difference in average pain intensity between people with OSA and CP and people with COMISA and CP?
Longitudinal
1. What are the short- (3 months) and long-term (6 months) clinical outcomes (average pain intensity, fatigue, sleepiness, sleep quality, depression, anxiety, quality of life) of CPAP treatment for patients with clinically relevant OSA and comorbid CP?
2. Does average pain intensity measured at 3 and 6-month follow-up differ between patients that show CPAP adherence (= use of CPAP for a minimum of four hours each night on at least 70% of the monitored nights) compared to patients with non-adherence (= use of CPAP for a less than four hours each night on at least 70% of the monitored nights)?
3. Is average pain intensity at baseline a predictor for CPAP adherence in people with CP and comorbid clinically relevant OSA as measured at 3-month follow-up.
4. Is there a difference in pain outcomes measured at follow-up points at 3 and 6 months between people with CP and COMISA compared to patients with only OSA and CP?
5. Is there a difference in self-reported health status with CPAP therapy at 3 and 6-month follow-up between people with clinically relevant OSA and CP compared to those without CP?
6. Are average hours of CPAP use per night (continuous variable) associated with average pain intensity at 6-month follow-up in people with CP and OSA?
7. Is AHI at baseline associated with average pain intensity at 6-month follow-up in people with CP and OSA?
Sensitivity and subgroup analyses will analyse data for people with headaches and other chronic pain separately considering headaches to be a very common direct consequence of OSA.
