Prognostic factors for long-term improvement in pain and disability among patients with persistent low back pain

Prognostic research in low back pain (LBP) is essential for understanding and managing the condition. This study aimed to, (1) describe the proportions with mild-moderate and severe pain and disability at baseline, 1-year and 4-year follow-up, and (2) investigate prognostic factors for improvement in pain and disability over 4 years in a cohort of secondary care LBP patients.

This was a secondary analysis of a cohort of patients with LBP aged 18-40 years recruited from a non-surgical outpatient spine clinic between March 2011 and October 2013 (n = 1037). Questionnaires were collected at baseline, 1-year, and 4-year follow-up. Disability was assessed using the Roland Morris Disability Questionnaire (RMDQ 0-100) and pain intensity using the Numeric Rating Scale (NRS 0-10). 'Mild-moderate pain' was defined as NRS < 7 and 'severe pain' as NRS ≥ 7. Likewise, 'mild-moderate disability' was defined as RMDQ < 58.3, and 'severe disability' was RMDQ ≥ 58.3. In the prognostic analysis, improvement in pain and disability over 4 years was defined as meeting both criteria: decrease of ≥ 2 on the NRS and of ≥ 20.8 on the RMDQ. Sixteen candidate prognostic factors were assessed by multivariate logistic regression.

Among patients with information available at all three time points (n = 241), 54%/48% had persistent mild-moderate pain/disability, while only 7%/15% had persistent severe pain/disability. Of patients included in the multivariate prognostic analysis regarding improvement over 4 years (n = 498), 32% had improved in pain and disability after 4 years. Positive associations were found for pain intensity (OR 1.34 [95%CI: 1.17-1.54]), disability (OR 1.01 [1.00-1.02]), and regular employment or studying (OR 1.67 [1.06-2.64]), and negative associations for episode duration (OR 0.99 [0.99-1.00]) and risk of persistent pain (OR 0.58 [0.38-0.88]).

Patients with persistent LBP in secondary care had mostly mild-moderate pain and disability consistently at all three time points, with few having consistently severe symptoms over 4 years. Moreover, approximately half of the included patients improved in pain and disability. We found that pain intensity, disability, episode duration, regular employment or studying, and risk of persistent pain predicted a long-term improvement. However, the limited availability of complete follow-up data may affect generalisability.