An important measure of effect on the population level, used to calculate the impact on risk for disease, given a risk
factor intervention, is the potential impact fraction (PIF). The PIF is mostly calculated using a categorical risk factor distribution and a relative risk for each category. However, some risk factors,
such as hypertension and BMI, are much better described by continuous distributions.
When a PIF is calculated from a continuous risk factor distribution, it is necessary to calculate the integral
of the product of the risk factor distribution and the corresponding relative risk function (see the paper in the download for details). The risk factor integral add-in provides this functionality for
Several risk factor distributions and risk functions are available. A basic understanding of integration will be helpful to set correct integration boundaries.