Are obese patients more likely to develop diabetes? Are workers exposed to toxic substances more likely to develop lung cancer than those who are not? Are people with high cholesterol at greater risk of a cardiovascular event?
Questions of this kind can be answered only with a sample of individuals classified according to whether they have the disease and whether they have been exposed to the risk factor.
In the example below, the disease is cataracts and the risk factor is diabetes, but the same reasoning can be adapted to many other situations. It is also worth noting that a disease such as diabetes may itself depend on another risk factor, which could be obesity or even… cataracts!
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Theoretical and estimated odds ratios
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