Insomnia Symptoms and Chronic Pain among Patients Participating in a Pain Rehabilitation Program—A Registry Study

Insomnia and chronic pain are prevalent health complaints. Previous research has shown that they are closely associated, but their interaction and causality are not completely understood. Further research is needed to uncover the extent to which a treatment strategy focusing on one of the conditions affects the other. This study aimed to map the prevalence of insomnia symptoms among patients in interdisciplinary pain rehabilitation program (IPRP) and investigate associations between the degree of insomnia at baseline and the treatment outcome regarding pain intensity, physical function, social function, mental well-being, anxiety, and depression. Of the 8515 patients with chronic pain, aged 15–81 who were registered in the Swedish Quality Registry for Pain Rehabilitation during 2016–2019 and participated in IPRP, 7261 had follow-up data after treatment. Logistic regression analysis was used to investigate associations. The prevalence of clinical insomnia, according to Insomnia Severity Index (ISI), among chronic pain patients in IPRP was 66%, and insomnia symptoms were associated with both country of birth and educational level. After IPRP, the prevalence of clinical insomnia decreased to 47%. There were statistically significant associations between the degree of insomnia symptoms before IPRP and physical function (p < 0.001), social function (p = 0.004) and mental well-being (p < 0.001). A higher degree of insomnia symptoms at baseline was associated with improvement after IPRP. In conclusion, IPRP seem to have beneficial effects on insomnia symptoms in chronic pain patients. Nevertheless, almost half of the patients still suffer from clinical insomnia after IPRP. The possible effect of systematic screening and treatment of insomnia for improving the effect of IPRP on pain is an important area for future research.