Insomnia symptom severity predicts long-term pain intensity and bothersomeness across ICD-11 chronic pain categories: a registry-based cohort study.

Abstract

Objectives: Sleep and pain are reciprocally linked, each exacerbating functional impairments. In this observational cohort study, we examined differences in insomnia symptom severity among patients whose pain diagnoses, originally classified according to the International Classification of Diseases, 10th edition (ICD-10), were transformed into ICD-11 chronic pain categories. We further investigated whether the severity of insomnia symptoms at intake at a specialized pain clinic could predict pain outcomes 12 months later.

Methods: Data were drawn from 4,283 patients registered in the Oslo University Hospital Pain Registry. Baseline data from 3,705 patients were analyzed for differences in insomnia severity (measured using the Insomnia Severity Index, ISI) across ICD-11 chronic pain categories. At follow-up, 1,163 patients were included to test whether baseline insomnia severity predicted pain intensity and bothersomeness at 12-month follow-up using hierarchical linear regression models.

Results: The severity of insomnia symptoms (0-28, ISI) was slightly lower in chronic primary pain (Mean 15.3, SD=6.77) compared to chronic neuropathic pain (Mean 16.3, SD=6.65), adjusted p=0.017. No differences were observed between other chronic pain categories. After adjusting for age, gender, baseline pain scores, and psychological characteristics, a higher baseline severity of insomnia symptoms predicted greater pain intensity and bothersomeness at follow-up.

Conclusions: While the severity of insomnia symptoms appears to be equally distributed across ICD-11 chronic pain categories and has a substantial impact on the long-term intensity and bothersomeness of pain, it is largely ignored in clinical guidelines. Findings suggest that early, targeted interventions for insomnia symptoms may benefit patients.