Intended for healthcare professionals


Smoking and dementia in male British doctors

BMJ 2000; 321 doi: (Published 05 August 2000) Cite this as: BMJ 2000;321:378

Authors did not, strictly speaking, compare smokers with non-smokers

  1. Eric Boyd (, facilities manager
  1. University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
  2. 16 Roskear, Camborne, Cornwall TR14 8DN
  3. Clinical Trial Service Unit and Epidemiological Studies Unit, Radcliffe Infirmary, Oxford OX2 6HE

    EDITOR—Doll et al's finding that “persistent smoking does not substantially reduce the age specific onset rate of Alzheimer's disease or of dementia in general” is not surprising.1 The authors didn't compare smokers with non-smokers.

    By combining lifelong non-smokers and ex-smokers in the non-continuing group they effectively stopped comparing smokers with non-smokers. To complicate the issue further they then note, “As questionnaires were sent out only every six to 12 years, the mean time before death that the relevant smoking habits had been recorded was not 10 but 15 years.” In the end this study compares a group including non-smokers and ex-smokers who may have started smoking in the previous 15 years with a group of smokers who may have stopped in the previous 15 years.

    Has the BMJ fallen prey to the concerted and unrelenting efforts of health organisations determined to dictate an antismoking social policy rather than provide the honest and unbiased facts that people need to make informed personal choices? Or is the BMJ part of the team?


    • Competing interests None declared. …

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