where P(D) is the prevalence of overweight
and C1, …, Cm are all possible
combinations of the confounders.14 E
indicates that X = 0 holds for all
exposures X 2 E. The formula yields
the combined effect of all exposures
included in E. More precisely, it can be
used to determine the proportion of
cases of overweight that can be prevented
by eliminating all exposures in
E. For estimating the combined effect
of a subset T of E (eg, the preventable
exposures), the joint attributable risk
AR(T) must be adjusted not only for
the confounders but also for the remaining
exposures in E not included in
the subset T.14