New term may be needed for data categorisation

BMJ 2006; 332 doi: https://doi.org/10.1136/bmj.332.7551.1216-c (Published 18 May 2006) Cite this as: BMJ 2006;332:1216
  1. Charles Normand (charles.normand{at}tcd.ie), Edward Kennedy professor of health policy and management
  1. Trinity College Dublin, Dublin 2, Republic of Ireland

    EDITOR—Altman and Royston have done a great service in discouraging the categorisation of continuous data in health research.1

    A particularly bad case of this is the tendency of researchers (and indeed public statistical agencies) to use often broad age categories for data that originally had a single year of age. In addition to the serious statistical disadvantages of this practice, there has come to be a habit of believing that certain age cut-off points matter. The evidence is clear that being older than 65 has little relevance in terms of disease or healthcare costs, and the patterns found are of continuous twice differentiable curves.

    Perhaps we should encourage use of a new term such as “evidence destruction” in place of the more neutral “data categorisation.”


    • Competing interests None declared.


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