Vitamin Information Center

Attributable Risk Fraction
Definition
The attributable risk fraction is an epidemiological
parameter. If there are several causes for the development
of a health problem, the attributable risk fraction
describes the percentage of the risk that is due to a certain
risk factor, e. g. the percentage of risk for lung cancer
caused by smoking.

Attributable Risk (AR)
Definition
Attributable risk (AR) is the proportion of the incidence
of a disease in exposed individuals that is due to exposure.
It is the incidence of a disease in the exposed
population that would be eliminated if exposure were
eliminated. It can be calculated as rate difference (the
rate in the exposed group minus the rate in the unexposed
group) or risk difference (the difference between
the risks in the exposed and unexposed groups). When
the level of risk in both exposed and unexposed groups
is the same, the risk difference is 0. If an exposure is
harmful (e. g., cigarette smoking), the risk difference is
expected to be greater than 0. If an exposure is protective
(e. g., vaccine), the risk difference will be less
than 0.
The AR is sometimes referred to as attributable risk in
exposed individuals because it is used to quantify the
risk that can be attributed to exposure in the exposed
group. The AR is the measure of association that ismost
relevant when making decisions for individuals.
Attributable risk percent (AR%) is the percent of the
incidence of a disease that is due to exposure in exposed
individuals. It is the percent of the incidence of a disease
in the exposed population that would be eliminated
if exposure were eliminated.