Risk factors and their identification. Third Part: Examples.

This is the final of a series of three articles in Diabete & Metabolisme which reviews the identification of risk factors of a disease, here: diabetes or complications of diabetes. In the first of the series [1], we gave the definition of a risk factor, along with measures of its force-relative risk and odds ratio, followed by the epidemiological definitions of the diseases: diabetes, coronary heart disease and hypertension. Risk factors were further discussed and we completed the discussion by some observations on the bias which can arise from a study or from its analysis, which can lead the researcher to the wrong conclusion. The three types of epidemiological studies which are used to determine whether factors are associated with a disease: observational or cross-sectional studies, cohort studies and case-cohort studies are described in the second of the series [2]. Examples were provided of each of these study types and their advantages and disadvantages were discussed. This final paper provides some examples of the study types and the identification of risk factors from the literature. The first examples involve diabetes and pancreatic cancer, the second birth weight and non-insulin dependent diabetes. Having found an association between a risk factor and a disease, we then discuss whether it can be considered to be a risk factor, and if so and whether it is likely to be a cause of the disease.