The main purpose of this project is to conduct a prospective cohort study in order to better understand the importance of insomnia symptoms in patients referred to interdisciplinary rehabilitation due to chronic pain. Moreover, this project will also raise awareness on how insomnia symptoms, alone, and in interplay with factors such as function, psychological distress, physical activity, and fatigue impact on patient's prognosis and work ability. Our aim is that this knowledge can be used to design new interventions and improve rehabilitation programs for this patient group.

Insomnia is a vast problem among patients with chronic musculoskeletal pain. Despite the close relation between pain and sleep, sleep quality has received little attention in rehabilitation programs for patients with pain. So far, there is a lack of studies investigating the association between insomnia and chronic pain in patients referred to interdisciplinary rehabilitation. Identifying subgroups of the population with higher burden of poor sleep will aid clinicians to tailor treatment and prevention strategies. Moreover, knowledge on how insomnia symptoms fluctuate throughout the rehabilitation program and how insomnia symptoms interact with factors such as mental distress, physical activity, and fatigue impact on patient's recovery (e.g., the prognosis of pain, quality of life, and work participation) can be used to develop and implement more successful rehabilitation programs.

This is a cohort study primarily designed to address sleep problems in patients referred for pain rehabilitation by using questionnaire data from the rehabilitation centers linked to registry data. This study will constitute both a cross-sectional survey among patients referred to rehabilitation before they participate in rehabilitation. In addition to questionnaires, administrative data and clinical data, these data will be linked to national health registries on prescriptions, health care use and sickness absence. Potential participants are patients referred to rehabilitation at five different Unicare rehabilitation centers in Norway (Unicare Helsefort, Unicare Coperio, Unicare Hokksund, Unicare Friskvern and Unicare Jeløy) due to long-term pain complaints.

Inclusion Criteria:

• Take part in rehabilitation for long-term pain complaints at one of the five centers
• Consented to research

Exclusion Criteria:

• None

Potential participants are patients referred to rehabilitation at five different Unicare rehabilitation centers in Norway (Unicare Helsefort, Unicare Coperio, Unicare Hokksund, Unicare Friskvern and Unicare Jeløy) due to long-term pain complaints. Potential participants are referred to outpatient or inpatient rehabilitation or a shorter assessment stay (where the goal is to assess what is the best treatment option for the patient). Referrals to the rehabilitation centers are done by the patients' general practitioner or by specialist healthcare. All referrals are considered at the regional unit for referrals (Regionalt henvisningsmottatak) in mid- or southeast Norway who judge whether they fulfill the criteria for rehabilitation in specialist health care.