Which statement is true about the relationship between population attributable risk (PAR) and relative risk (RR)?

• A. PAR estimates population-level disease burden attributable to exposure; RR compares risks between exposed and unexposed.
• B. RR estimates population-level disease burden attributable to exposure; PAR compares risks between exposed and unexposed.
• C. PAR is the difference in risk between exposed and unexposed; RR is the ratio of prevalence.
• D. RR is used to estimate the burden of disease in a population.

Answer: (A)

The key idea here is understanding what each measure tells us. PAR captures the disease burden in the whole population that is attributable to an exposure—essentially, how many cases could be avoided if the exposure were eliminated. It reflects population impact and depends on both how strongly the exposure raises risk and how common the exposure is in the population.

Relative risk, on the other hand, is a measure of association. It compares the risk of disease in those exposed to the risk in those not exposed, but it does not by itself tell you how many cases exist in the population.

Because PAR depends on both the strength of the association (RR) and the exposure prevalence, it represents population-level burden rather than just a comparison. For example, the same RR can yield a larger PAR if a larger portion of the population is exposed, and a smaller PAR if exposure is rare.

That’s why the statement that PAR estimates population-level disease burden attributable to exposure and RR compares risks between exposed and unexposed is the best fit. The other ideas misstate what each measure represents: PAR is not just a simple difference in risk between groups, and RR is not a direct measure of population burden.