Presence of a potential biological mechanism.ĭoes the relationship agree with the current knowledge of the natural history/biology of the disease?ĭoes the removal of the exposure alter the frequency of the outcome?Īccording to Rothman, while Hill did not propose these criteria as a checklist for evaluating whether a reported association might be interpreted as causal, they have been widely applied in this way. ![]() ![]() There must be a one to one relationship between cause and outcome.Ĭhange in disease rates should follow from corresponding changes in exposure (dose-response). Have the same findings must be observed among different populations, in different study designs and different times? The Bradford-Hill criteria (J Roy Soc Med 1965:58:295-300)Īccording to Hill, the stronger the association between a risk factor and outcome, the more likely the relationship is to be causal. The Bradford-Hill criteria are widely used in epidemiology as providing a framework against which to assess whether an observed association is likely to be causal. The judgement as to whether an observed statistical association represents a cause-effect relationship between exposure and disease requires inferences far beyond the data from a single study and involves consideration of criteria that include the magnitude of the association, the consistency of findings from other studies and biologic credibility. Conversely, the absence of an association does not necessarily imply the absence of a causal relationship. Therefore, an observed statistical association between a risk factor and a disease does not necessarily lead us to infer a causal relationship. That is, the observed association may in fact be due to the effects of one or more of the following: However, since most epidemiological studies are by nature observational rather than experimental, a number of possible explanations for an observed association need to be considered before we can infer a cause-effect relationship exists. Resource textĪ principal aim of epidemiology is to assess the cause of disease. Learning objectives: You will learn basic concepts of causation and association.Īt the end of the session you should be able to differentiate between the concepts of causation and association using the Bradford-Hill criteria for establishing a causal relationship.
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