Page 370 - Week 02 - Wednesday, 13 May 1992
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of course, later today we will be considering a Bill that deals with fluoride, an area where perhaps more than anywhere else we have seen cases of what Professor Doll refers to as claims about the existence of hazards based on half-baked and preliminary findings -
bias in reporting, and complexity caused by the way different social and environmental factors are interrelated. They may consequently cause much unnecessary work for professional epidemiologists and much unnecessary anxiety for the public, which could be avoided if there were more general understanding of the power and the limitations of epidemiological investigation.
What is epidemiology, apart from a word that is difficult to pronounce? An epidemiologist works initially on a suspicion or an idea that there is a problem. That suspicion or idea may come from laboratory research, disease patterns, clinical practice or theoretical speculation. From that idea an hypothesis is usually formed and then the epidemiologist tests that hypothesis. The epidemiologist can test the hypothesis in two normal ways. One is with a descriptive study and the other is with an analytical study.
Descriptive studies fall into the categories of cross-sectional surveys and cohort or case control studies. Intervention studies are the normal method of carrying out analytical or clinical studies. The most obvious of the analytical studies are those done on new drugs introduced by pharmaceutical companies, to assess whether they are safe or not. They involve a control group and a study group.
To get a background to epidemiology, it is very interesting to look at the first really great case, which was put together by a man called John Snow in the 1840s. He had a suspicion about cholera deaths in London. His research took the form of knocking on doors to find out how many people had died from cholera and in what areas. He then looked at the results and was able to determine that death rates from cholera were particularly high in areas where three water companies provided water. Those three water companies were the Lambeth company, the Vauxhall company and the Southwark company.
Between 1849 and 1854 the Lambeth company moved its water intake in the Thames away from a sewerage outlet. It was John Snow who noted a significant drop in the number of deaths from cholera in the area where that company was providing water. One can draw all sorts of conclusions about whether we should have privatisation of water supplies, or whether we should use additives such as chlorine in water. Nevertheless, I think the point of the epidemiological study was that John Snow was able to draw particular conclusions that had a significant - in fact, massive - impact on the health of society. That is exactly what epidemiology is about.
We normally think of "epidemiology" as coming from the word "epidemic"; so we think of it in terms of a study of epidemics and health. But it is, in fact, broader than that. Epidemiology also includes the study of population health. Recent epidemiological studies in population health include studies associated with AIDS, abortion, and the health of disadvantaged groups such as women, Aborigines and drug users.
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