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Smoking and the brain

BMJ 2000; 320 doi: (Published 22 April 2000) Cite this as: BMJ 2000;320:1087

No good evidence exists that smoking protects against dementia

  1. Carol Brayne, lecturer in epidemiology (
  1. Department of Public Health and Primary Care, Institute of Public Health, Cambridge CB2 2SR

    Papers p 1097

    Smoking prevents dementia? Smoking causes dementia? Over the past decade a succession of research findings has produced apparently conflicting evidence on this question. In the early 1990s results from case-control and family studies suggested a protective effect.1 2 The findings were widely reported,3 including in the mass media, and some scientists stated publicly that they would consider taking up smoking if they had a family history of dementia.

    Tobacco companies began to sponsor conferences on dementia, perhaps because it seemed to offer them a lifeline in an otherwise relentless sequence of findings about the deleterious effects of smoking. If smoking reduced life expectancy and also reduced the likelihood of survivors developing dementia then, from a policy perspective, there might be a role for the habit in later life.

    The potential protective effects have some biological plausibility. Alzheimer's disease affects neurotransmitter systems, particularly the cholinergic system. Nicotine is a cholinergic agonist. The effect of nicotine on cognition, attention, …

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