Abstract
Both the absolute risk and the relative risk (RR) have a crucial role to play in epidemiology. RR is often approximated by odds ratio (OR) under the rare-disease assumption in conventional case-control study; however, such a study design does not provide an estimate for absolute risk. The case-base study is an alternative approach which readily produces RR estimation without resorting to the rare-disease assumption. However, previous researchers only considered one single dichotomous exposure and did not elaborate how absolute risks can be estimated in a case-base study. In this paper, the authors propose a logistic model for the case-base study. The model is flexible enough to admit multiple exposures in any measurement scale—binary, categorical or continuous. It can be easily fitted using common statistical packages. With one additional step of simple calculations of the model parameters, one readily obtains relative and absolute risk estimates as well as their confidence intervals. Monte-Carlo simulations show that the proposed method can produce unbiased estimates and adequate-coverage confidence intervals, for ORs, RRs and absolute risks. The case-base study with all its desirable properties and its methods of analysis fully developed in this paper may become a mainstay in epidemiology.
Highlights
Both the absolute and the relative disease risks have a crucial role to play in epidemiology
It can be seen that our method can produce unbiased estimates and adequate-coverage 95% confidence intervals (CIs) for odds ratio (OR), relative risk (RR), and risks
Exhibit S3 shows that our method can produce unbiased estimates and adequate-coverage 95% CIs for ORs, RRs, and risks, when the exposure is in a continuous scale
Summary
Both the absolute and the relative disease risks have a crucial role to play in epidemiology. The relative risk (RR) is the ratio of the disease risk for individuals at one specific exposure level to the disease risk for those at a reference level. Under the rare-disease assumption, RR is approximated by the odds ratio (OR), which in turn can be conveniently estimated in a case-control study. While an index such as RR or OR may be adequate for etiologic inferences, it is only part of a story. Once a factor has been demonstrated to be a risk factor for the disease, we will often be asked to predict the disease risk of an individual having a specific level of an exposure—the absolute risk. The conventional case-control study does not provide an estimate for it
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