Estimating the prevalence of chronic insomnia in patients with non-cancer chronic pain: Study protocol of a multicenter cross-sectional study

Background: Chronic non-cancer pain (CNCP) and insomnia frequently co-occur, creating a bidirectional cycle in which pain disrupts sleep, and poor sleep heightens pain perception. Despite mounting evidence suggesting high comorbidity, no studies have explored this relationship in the Spanish population. This study aims to estimate the prevalence of chronic insomnia among CNCP patients and examine its associations with pain intensity, sleep quality, psychological symptoms, and medication use. Methods and analysis: This will be a multicenter, cross-sectional prevalence study involving 15 pain units across Catalonia, Spain. Adult patients with a known CNCP diagnosis under specialist care will be invited to participate. Data will be collected during a single study visit using electronic medical records and a structured battery of validated self-report questionnaires, including the Insomnia Severity Index, Brief Pain Inventory, Pittsburgh Sleep Quality Index, Hospital Anxiety and Depression Scale, Profile of Mood States, short form-12 health survey, and EuroQol-5 Dimensions-3 Level. The primary outcome is the prevalence of chronic insomnia. Secondary outcomes include associations with pain severity, sleep quality, mood, quality of life, and hypnotic drug use. Descriptive statistics and Poisson regression with robust variance will be used to estimate prevalence ratios and 95% confidence intervals. Ethics and dissemination: The study has received ethical approval from the coordinating site ( Hospital del Mar Research Institute ; reference 2025/11914) and will obtain local approvals at participating centers. Informed consent will be obtained from all participants. Results will be disseminated via peer-reviewed journals and scientific conferences, regardless of outcome.