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Smoking Does Not Protect the Brain Against Dementia or Alzheimer's Disease

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-- Editor,

Smoking does not protect against dementia or Alzheimer's disease, according to a study in the British Medical Journal (BMJ), contradicting the implications of some earlier research.

Sir Richard Doll and colleagues from the Clinical Trial Service Unit and Epidemiological Studies Unit, Radcliffe Infirmary at Oxford reported on observations of over 34,000 male British doctors whose smoking habits have been reviewed every six to 12 years since 1951 to determine the impact on their health. The research team also reviewed the published data on the associations between smoking and Alzheimer's disease.

Over 24,000 of the doctors had died by the end of 1998. Dementia was mentioned on the death certificates of 483. Among 473 whose smoking habits were recorded at least 10 years before their death, when they would not have been influenced by the start of the disease, the prevalence of both Alzheimer's disease and of other types of dementia was similar in both smokers and non-smokers.

If anything, persistent smoking may increase rather than decrease the age specific onset rate of dementia, conclude the authors.

The prior suggestions that smoking might be protective, say the authors, came from studies that were flawed because they were too small, or had relied on information about smoking habits from people other than the sufferers themselves.