Objectives: Cost-effectiveness analysts
often present cost-effectiveness results by age to help inform
decisions about the use of an intervention. Yet it is not known how
well studies model the risks and costs associated with age. We
reviewed published studies to examine their modeling of age
differences.
Methods: MEDLINE searches identified all cost-effectiveness analyses
published between 1985 and 1997 that included adults 50 years of age and older,
were based on data for developed countries, and compared
cost-effectiveness ratios for adults of different ages or for
initiation of an intervention at different ages; 36 articles met
these criteria. They were reviewed to determine the extent to which
they incorporated age-specific data. Studies that justified using
the same data for all ages were counted as having varied the data
element by age.
Results: All studies varied life expectancy by age. Most also varied
the incidence/prevalence of the target condition and the case
fatality rate. Only 36% varied the effectiveness rate of the
intervention by age. Costs were usually assumed constant: 42% of
studies varied the cost of treating adverse effects and 17% varied
the cost of treating the target condition. Whether a data element
was varied did not appear to be related to the pattern of
cost-effectiveness ratios by age.
Conclusions: Many studies have not modeled age differences in
sufficient detail to ensure that differences in cost-effectiveness
ratios by age are accurate and a sound basis for decisions. As
cost-effectiveness analysis becomes more widespread, analysts should
strive to incorporate more complete age-specific data.