Endgames Statistical Question

Hazards and hazard ratios

BMJ 2012; 345 doi: http://dx.doi.org/10.1136/bmj.e5980 (Published 07 September 2012) Cite this as: BMJ 2012;345:e5980
  1. Philip Sedgwick, reader in medical statistics and medical education
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}sgul.ac.uk

Researchers investigated the risk of colorectal cancer after screening with flexible sigmoidoscopy. A randomised controlled study was undertaken in Norway with a population based sample. The intervention consisted of once only flexible sigmoidoscopy screening with or without a single round of faecal occult blood testing. The control treatment was no screening. The main outcome measures included length of time from randomisation until death from colorectal cancer.1

After a median of six years of follow-up, the hazard ratio for mortality from colorectal cancer, comparing intervention with control, was 0.73 (95% confidence interval 0.47 to 1.13). The researchers concluded that mortality from colorectal cancer was not significantly reduced in the screening group but that it seemed to be lower among participants who attended screening.

  • Which of the following statements, if any, are true?

  • a) The hazard of death from colorectal cancer represents the instantaneous rate of death at any time during follow-up.

  • b) …

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