Relative risk can be estimated in a case-control study by a calculation called the odds ratio. The odds ratio is a method of estimating relative risk in a case-control study where it is not possible to calculate the rate of developing disease in the presence or absence of exposure. Instead the ratio of the odds of exposure among cases and among controls can be calculated. See the 2x2 table below. Attributable Risk Attributable risk estimates the likelihood of disease in exposed individuals related to nonexposed individuals.
Attributable risk estimates the excess risk of disease in the exposed compared to the nonexposed.
Attributable risk quantifies the risk of disease in the exposed group attributable to the exposure by subtracting the risk that would have otherwise occurred in the nonexposed. If there is no association between exposure and disease, there is no difference between incidence rates in the exposed and nonexposed. A positive attributable risk indicates the number of disease cases attributable to the exposure. It also indicates the number of disease cases among the exposed that could be eliminated if the exposure were eliminated. During the same time period, the lung cancer rate in nonsmoking females was 12 per 100,000.