Incidence rates

BMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e1589 (Published 07 March 2012) Cite this as: BMJ 2012;344:e1589
  1. Philip Sedgwick, senior lecturer in medical statistics
  1. 1Centre for Medical and Healthcare Education, St George’s, University of London, Tooting, London, UK
  1. p.sedgwick{at}sgul.ac.uk

The association between use of proton pump inhibitors and risk of hip fracture was investigated in postmenopausal women. Women who were enrolled in the Nurses’ Health Study, a prospective cohort study, provided data biennially from 2000 until June 2008. The primary outcome was time until first hip fracture. The incidence rate of hip fracture was higher among regular users of proton pump inhibitors than non-users (2.02 versus 1.51 per 1000 person years).1

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

  • a) An incidence rate represents the proportion of women who experienced hip fractures.

  • b) Women using proton pump inhibitors had a greater risk per year of hip fracture than non-users.

  • c) The risk of hip fracture is assumed to be equal for each year of follow-up.


Statements b and c are true, whereas a is …

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