Outcome measures
death, sickness or disability, disability
DISORDERS, MUSCULOSKELETAL DISORDERS
The primary outcome was the number of sickness absence days during a 12-month period following randomization. Secondary work outcomes were time until sustainable RTW, which was defined as a period of four consecutive weeks without any benefits (sick leave payments, work assessment allowance or disability pension), and probability of not receiving benefits each month during follow-up. For participants with a graded disability benefit at inclusion any increase in disability pension during follow-up was counted as sick leave. Sick leave data was obtained from the Norwegian National Social Security System Registry, where all individuals receiving any form of sickness or disability benefits in Norway are registered by their social security number. Based on information from the different medical benefits (sick-leave payments, work assessment allowance and disability pension), we calculated the equivalent of full workdays on medical benefits according to a 5-day workweek for every month during follow-up. We also used data from the registry on main diagnoses for sick leave and information about emigration and death. The diagnoses are coded according to the International Classification of Primary Care, second edition (ICPC-2),and were collapsed into three groups: musculoskeletal disorders, mental health disorders, and other.Other variables registered by questionnaires at inclusion were level of education, dichotomized as high (college/university) or low, subjective health evaluation (scored as poor, not so good, good, or very good) and employment percentage (continuous). Employment percentage was measured by a question about how much they used to work before being sick listed, ie, percentage of full-time employment (0–100%).