Intended for healthcare professionals

Endgames Statistical Question

Hazard ratios

BMJ 2010; 341 doi: (Published 25 August 2010) Cite this as: BMJ 2010;341:c4566
  1. Philip Sedgwick, senior lecturer in medical statistics1,
  2. Louise Marston, research statistician2
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London
  2. 2Department of Primary Care and Population Health, University College London, London
  1. Correspondence to: P Sedgwick p.sedgwick{at}

    Previous questions described survival (time to event) data.1 2 The example used was a randomised controlled trial, which compared the effectiveness of an integrated care programme with usual care in facilitating the return to work for patients with chronic low back pain.3 The integrated care programme was a combined patient and workplace directed intervention. Trial participants were adults aged 18-65 years, who had had low back pain for more than 12 weeks, were in paid work, and were absent or partially absent from work.

    The primary outcome was duration of time off work after randomisation until a fully sustained return to work. Trial participants were followed for 12 months (figure). Integrated care was more effective than usual care in reducing disability and facilitating a return to work (hazard ratio 1.9, 95% confidence interval 1.2 to 2.8).

    Kaplan-Meier survival curves for the integrated and usual care interventions of the time until a fully sustained return to work for patients with chronic low back pain

    Which of the following, if any, are true?

    • a) At any time during follow-up, patients on integrated care were …

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