Effects of Interdisciplinary Treatment on Sickness Absence in Patients With Chronic Pain

This is a completely register-based observational cohort study. The study population is defined from the Swedish Quality Registry for Pain Rehabilitation (SQRP), which routinely aggregates data from specialist IDT pain management clinics across Sweden. SQRP contains information on the exposure/intervention: whether a patient that visited a SQRP-affiliated clinic was allocated to an IDT program (test) or not (control); t0 defined as the day of the IDT assessment. Microdata from SQRP is linked to other Swedish registers via the unique personal identification number held by all Swedish residents. Outcome data is obtained from the Swedish Social Insurance Agency. Registers managed by the National Board of Health and Welfare include data on dispensed prescription pharmaceuticals and specialist health care.

Markov multistate survival-based methods will be used to compare the sickness absence between groups. Specifically, length of stay per sickness absence state (no sickness absence, sick leave, and disability pension) will be compared over five years from t0. Both crude and adjusted estimates will be presented. Adjustment will be made based on our hypothesis about causal relationships and include: history of sickness absence, sociodemographics (age, sex, sociodemographic status), patient disability (emotional distress, everyday interference, and confidence in future improvement), and governmental policy (IDT assessment year and geographical region of IDT clinic).