From a public health standpoint, this is often both the critical issue and the question that is raised by policy-makers and by those responsible for funding prevention programs. They may want to know what the proposed program is going to do for the community as a whole. How is it going to change the burden on the health care system or the burden of suffering in the entire community, not just in exposed individuals? For example, if all smokers in the community stopped smoking, what would be the impact of this change on the incidence of lung cancer in the total population of the community (which includes both smokers and nonsmokers)?
* The incidence in the population that is due to the exposure can also be calculated as follows: Attributable risk for the exposed group × Proportion of the population exposed.
* Another way to calculate the attributable risk for the total population is to use Levin—s formula, which is given in the appendix to this chapter.