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The different types of epidemiological study

Cahiers d'études et de recherches francophones / Santé . Volume 2, Number 1, 49-54, Janvier-Février 1992, Note méthodologique

Résumé

Summary

Author(s) : Jacques Drucker, Alain Moren, François Dabis, Laboratoire de santé publique, faculté de médecine, Université François-Rabelais, 2 bis, boulevard Tonnelle, BP 3223, 37032 Tours Cedex, France, Épicentre, 8, rue Saint-Sabin, 75011 Paris, France, INSERM U. 330, Université de Bordeaux II, 146, rue Léo-Saignat, 33076 Bordeaux Cedex, France..

Summary : Most epidemiological studies are observational and can be classified into three major types: case-control, cohort and transversal studies. As subjects cannot be randomly allocated to exposure or disease groups in any of these types of study, the investigator must pay particular attention to intergroup comparability. Case-control studies involve selection of subjects on the basis of disease status, while cohort studies are based on exposure status. Both approaches have advantages and disadvantages, which are discussed in this article. Observational studies are rarely able to demonstrate a direct causal relationship between exposure to a risk factor and the occurrence of a disease, even though a number of criteria, such as dose-effect, consistency, specificity, temporality and biological plausibility, have been established. Observational studies are therefore powerful methodological tools for the epidemiologist.

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