Intended for healthcare professionals

Endgames Statistical question

Cohort studies

BMJ 2010; 340 doi: (Published 25 February 2010) Cite this as: BMJ 2010;340:c1002
  1. Philip Sedgwick, senior lecturer in medical statistics
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London SW17 0RE
  1. p.sedgwick{at}

    Researchers investigated whether increased body mass index was a risk factor for prostate cancer.1 Data from a prospective cohort study known as the Health Professionals Follow-Up Study was used.2 In this study, 51 529 American health professionals aged between 40 and 75 years responded to a postal questionnaire. The health professionals were recruited in 1986 and self reported that they were free of prostate cancer at the start of the study. Participants were then followed up at regular intervals until 1994.

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

    • a) The …

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