Which measure can describe the burden of disease in the population attributable to exposure?

• A. Relative Risk
• B. Population Attributable Fraction
• C. Sensitivity
• D. Specificity

Answer: (B)

The measure describes the share of disease cases in the population that are due to a specific exposure, i.e., the portion of cases that could be prevented if the exposure were eliminated, assuming the exposure causes the disease. It combines how strongly the exposure increases risk with how common the exposure is in the population.

This is captured by the population attributable fraction. It depends on the strength of the association between exposure and disease (relatives risk) and the prevalence of the exposure in the population. A common form is PAF = Pe × (RR − 1) / [Pe × (RR − 1) + 1], where Pe is the proportion exposed and RR is the relative risk. For example, if half the population is exposed (Pe = 0.5) and the exposure doubles risk (RR = 2), the PAF would be about 33%, meaning roughly one-third of cases could be prevented if the exposure were eliminated.

This measure is useful for public health planning because it reflects the potential impact of removing the exposure on the overall disease burden. Relative risk, by contrast, tells how much more likely disease is among the exposed compared with the unexposed but does not indicate how much of the population’s disease burden is attributable to the exposure. Sensitivity and specificity describe test performance, not disease burden in the population.