Background: Non-specific spinal pain (NSP), comprising back and/or neck pain, is one of the leading disorders in long-term sick-listing. During 2000-2004, 125 Swedish primary-care patients with non-acute NSP, full-time sick-listed 6 weeks-2 years, were included in a randomized controlled trial to compare a cognitive-behavioural programme with traditional primary care. This prospective cohort study is a re-assessment of the data from the randomized trial with the 2 treatment groups considered as a single cohort. The aim was to investigate which baseline variables predict a stable return-to-work during a 2-year period after baseline: objective variables from function tests, socioeconomic, subjective and/or treatment variables. Stable return-to-work was a return-to-work lasting for at least 1 month from the start of follow-up. Methods: Stable return-to-work was the outcome variable, the above-mentioned factors were the predictive variables in multiple-logistic regression models, one per follow-up at 6, 12, 18 and 24 months after baseline. The factors from univariate analyzes with a p-value of at most .10 were included. The non-significant variables were excluded stepwise to yield models comprising only significant factors (p < .05). As the comparatively few cases made it risky to associate certain predictors with certain time-points, we finally considered the predictors which were represented in at least 3 follow-ups. They are presented with odds ratios (OR) and 95% confidence intervals. Results: Three variables qualified, all of them represented in 3 follow-ups: Low total prior sick-listing (including all diagnoses) was the strongest predictor in 2 follow-ups, 18 and 24 months, OR 4.8 [ 1.9-12.3] and 3.8 [1.6-8.7] respectively, High self prediction (the patients' own belief in return-to-work) was the strongest at 12 months, OR 5.2 [1.5-17.5] and Young age (max 44 years) the second strongest at 18 months, OR 3.5 [1.3-9.1]. Conclusions: In primary-care patients with non-acute NSP, the strong predictors of stable return-to-work were 2 socioeconomic variables, Low total prior sick-listing and Young age, and 1 subjective variable, High self-prediction. Objective variables from function tests and treatment variables were non-predictors. Except for Young age, the predictors have previously been insufficiently studied, and so our study should widen knowledge within clinical practice.
