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Ecological studies are a poor means of testing aetiological hypotheses

BMJ 1998; 317 doi: (Published 05 September 1998) Cite this as: BMJ 1998;317:678
  1. Shah Ebrahim, Professor of clinical epidemiology,
  2. George Davey Smith, Professor of clinical epidemiology
  1. Royal Free Hospital School of Medicine, University College London Medical School, London NW3 2PF
  2. Department of Social Medicine, University of Bristol, Bristol BS 2PR

    EDITOR—The declines in cardiovascular diseases in Poland, “apparently without precedent in peacetime,”1 are similar to the declines seen in Britain over the same period.2 The table shows secular declines in mortality from cardiovascular diseases in Britain: between 1991 and 1994, death rates from both ischaemic heart disease and stroke fell dramatically, particularly among men at all ages and women aged over 55 years. In Britain these death rates are continuing to fall, in contrast to Poland. Furthermore, as mortality from ischaemic heart disease in Britain plateaued between 1980 and 1985 and then fell, the declines observed between 1985 and …

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