Which measure estimates the proportion of disease in the population that can be attributed to exposure?

• A. Relative risk
• B. Attributable risk
• C. Population Attributable Fraction
• D. Prevalence

Answer: (C)

The measure that estimates the portion of disease in the population that can be attributed to exposure is the population attributable fraction. It captures how much of the disease burden in an entire population could be prevented if the exposure were eliminated, by combining how common the exposure is with how strongly it raises risk. If an exposure is common and greatly increases risk, a large fraction of disease could be avoided; if the exposure is rare or only modestly increases risk, the potential prevention is smaller.

Relative risk looks at how much more likely disease is among the exposed compared with the unexposed, but it doesn’t tell you how much of the disease burden exists in the whole population. Attributable risk (risk difference) measures the excess risk among the exposed due to the exposure, not the population-wide burden. Prevalence is simply how widespread the disease is at a given time, not how much of that disease is due to a particular exposure.