The Danish Chiropractic Low Back Pain Cohort (ChiCo): Description and Summary of an Available Data Source for Research Collaborations.

Background: Back pain is among the most frequent reasons for care seeking globally. Observational clinical cohorts are useful for understanding why people seek care, the content of that care, and factors related to prognosis. This paper describes the Danish Chiropractic low back pain Cohort (ChiCo) and summarizes the primary characteristics of the population to inform the scientific community of the availability of these data as a resource for collaborative research projects.

Methods: Adults seeking chiropractic care for a new episode of non-specific back pain were enrolled at the initial visit and followed up after 2, 13, and 52 weeks, with a subpopulation having weekly follow-ups for 1 year. Patient-reported and clinical-reported data were collected in an electronic database using the REDCap software (REDCap Consortium, projectredcap.org). Variables were chosen to measure pre-defined research domains and questions and to capture information across health constructs deemed relevant for additional research. Non-responders at 13 and 52 weeks were contacted by phone to maximize follow-up data and explore differences on core outcomes between responders and non-responders.

Results: A total of 2848 patients (mean age 45 years, 59% men) were included from 10 clinics with 71%, 68% and 64% responding to follow-ups at 2, 13 and 52 weeks, respectively. Most participants (82%) were employed, nearly half reported current LBP for 1-7 days, and 83% had experienced LBP episodes previously. We did not identify indications of serious attrition bias.

Conclusion: We have described the aims and procedures for establishing the ChiCo cohort, characteristics of the cohort, and available information about attrition bias. These data have the potential to be linked, at an individual participant level, to the extensive Danish population-based registries that measure diverse health and social characteristics.