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Letters

Smoking and dementia in male British doctors

BMJ 2000; 321 doi: https://doi.org/10.1136/bmj.321.7257.378/a (Published 05 August 2000) Cite this as: BMJ 2000;321:378

Rapid Response:

Chalmers and Altman didn't; but Eysenck did!

In his comments on the paper by Richard Doll and his colleagues, Dr
Calinas-Correia suggests that Chalmers and Altman analysed the work of
Janerich et al about passive smoking and lung cancer. We didn't, but
Eysenck (1) did in a book that Doug Altman and I co-edited.

Hans Eysenck, like Ronald Fisher before him, promoted the notion that
the association between smoking tobacco and lung cancer is not causal, but
reflects a predisposition to both in people with certain genetic or
psychological characteristics. As Doll and Peto note in their response
(2) to Calinas-Correia, however, selective citation of evidence (whether
inadvertent or calculated) can be misleading.

The main message of the book that Calinas-Correia cites incorrectly
is that people reviewing research evidence should take steps to reduce
bias, and when possible, the effects of the play of chance. I hope that
the forthcoming 2nd edition (3) will succeed in communicating this message
more effectively than the 1st edition appears to have done!

Iain Chalmers

1. Eysenck HJ. Problems with meta-analysis. In: Chalmers I, Altman
DG, eds. Systematic reviews. London: BMJ Books, 1995.

2. Doll R, Peto R. Smoking and dementia in male British doctors. BMJ
2000;321:379.

3. Egger M, Davey Smith G, Altman DG (eds). Systematic reviews in
health care: meta-analysis in context. 2nd edition, BMJ Books, 2000.

Competing interests: No competing interests

05 August 2000
Iain Chalmers
Director
UK Cochrane Centre