0709-Measures of Excess Disease Occurrence II: Rate Difference and Attributable Rate

Lecture by Professor Omar Hasan Kasule Sr. for Year 2 Semester 1 medical student PPSD session on 12th September 2007.

Rate Difference (RD)

Rate difference (RD) is the difference in incidence between the exposed and the non exposed.

Attributable Rate (AR)

Attributable Rate (AR) is a measure of excess disease risk due to a particular exposure. It is determined as the proportion of cases in the total population that is attributable to the exposure (risk factor). It is a measure of the impact of eliminating a particular risk factor on disease risk.  

There are various mathematical formulations of AR that are beyond the scope of this session. They can be studied in advanced epidemiology courses. The simplest formulation based on the odds or rate ratio is as follows

  • AR% = (OR-1) / OR *100
AR%= (RR-1) / RR *100.

ŠProfessor Omar Hasan Kasule, Sr. September 2007