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Smoking and dementia in male British doctors: prospective study

BMJ 2000; 320 doi: (Published 22 April 2000) Cite this as: BMJ 2000;320:1097
  1. Richard Doll, emeritus professor of medicine,
  2. Richard Peto, director,
  3. Jillian Boreham, senior research fellow,
  4. Isabelle Sutherland, research assistant
  1. Clinical Trial Service Unit and Epidemiological Studies Unit, Radcliffe Infirmary, Oxford OX2 6HE
  1. Correspondence to: R Doll
  • Accepted 2 January 2000


Objective: To assess the possible association between smoking and dementia.

Design: Prospective study.

Setting: Cohort of British male doctors followed up since 1951.

Subjects: 34 439 male British doctors, with 24 133 deaths recorded.

Results: For all types of dementia combined the relative risk was 0.96 (95% confidence interval 0.78 to 1.18), based on 473 deaths at a mean age of 81 years. For probable or definite Alzheimer's disease, the relative risk in continuing smokers was 0.99 (0.78 to 1.25), based on 370 deaths at a mean age of 82 years. In aggregate, however, the other prospective studies indicate a direct, although not clearly significant, association between smoking and the onset of dementia in general and of Alzheimer's disease in particular.

Conclusions: Contrary to previous suggestions persistent smoking does not substantially reduce the age specific onset rate of Alzheimer's disease or of dementia in general. If anything, it might increase rather than decrease the rate, but any net effect on severe dementia cannot be large in either direction.


  • Funding The Medical Research Council has supported the study since 1951 and continues to do so through direct support of the Clinical Trial Service Unit and Epidemiological Studies Unit, helped by the Imperial Cancer Research Fund and British Heart Foundation.

  • Competing interests None declared.

  • Accepted 2 January 2000
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