thought she should have a mammogram, and ease of arrang-
ing transportation) mediated the effect of income on mam-
mography (Table 2). Other mediators included age and sev-
eral attitudes (believing that mammograms are frightening,
beneficial, important even without cancer signs; may detect
cancer that a clinician cannot find; provider recommendation;
being confused by contradictory information about mammog-
raphy). Mediators appeared to have a greater impact on ex-
plaining the income-mammography receipt relationship
among women with no prior mammography, with seven vari-
able individually having excess risk values 30%; age, em-
ployment, and believing that mammography is beneficial and
necessary at a given age individually accounted for 50% of
the relationship. After accounting for individual mediators in
our multivariable model in women with no previous mam-
mogram, there was no relationship between income and mam-
mography receipt (HR 0.91, 95% CI 0.41-2.00).
Our results were the same for women who had a previ-
ous mammogram with or without age adjustment and liv-
ing status adjustment in the base model. The relationship be-
tween income and mammography was attenuated when age
adjustment and living status adjustment were included in
the base model, but the mediators identified did not change.
We identified several attitudes and facilitating conditions
that mediated the effect of income on mammography use in
a population of women who have insurance coverage. Re-
gardless of a woman’s past behavior, three variables
emerged as important targets for future interventions: belief
in the necessity of mammograms, recommendations from
friends, and ease of arranging transportation to the ap-
pointment. Women with no prior mammography experience
reported several additional negative beliefs. If interventions
are able to change these attitudes and facilitating conditions,
mammography use may increase among low-income women
whose direct cost barrier has been removed. Interventionists
should direct their resources at addressing negative attitudes
and transportation issues when designing programs targeted
at low-income women with insurance.
This study also demonstrates that there can be disparities in
the uptake of mammography, and likely other preventive
healthcare, even among individuals with access to medical
care. Providing coverage for mammograms cannot be expected
to be sufficient to remove all barriers to its use; addressing the
importance of early detection and variables related to ease of
getting a mammogram must also be addressed to improve
screening among low-income populations. Addressing these
issues needs some careful thought, however, as the parent trial
explicitly addressed attitudes and facilitating conditions in mo-
tivational interviews that did not result in higher participation
than with simple reminder calls.
There are some limitations to our findings. First, the re-
sults may not be generalizable to women seeking care in the
general community who do not have health insurance or a
usual source of healthcare.
Low-income women with these
types of barriers to accessing healthcare probably have more
structural barriers to obtaining a mammogram. A second
limitation is our measure of income. We did not ask if these
women had additional assets. However, a study among
Medicare beneficiaries showed that low-income people
tended to have minimal assets; thus, our population is un-
likely to have substantial savings that might cause misclas-
sification and invalidation of the study findings.
information was missing for 19.6% of women, although non-
response was not related to mammography use. Thus, non-
response bias is not likely to threaten the validity of our find-
ings. Misclassification may result in women living alone or
in families both being included in the low-income group, but
this potential misclassification would tend to reduce the
strength of the relationship between income and mammog-
raphy use if women had more resources than we attributed
to them through our income level classification.
The age of the data might be of concern. Although some
variables may have changed since the data were collected,
the findings about beliefs, transportation, and provider rec-
ommendation are still important barriers to receiving mam-
mography among low-income women, as supported by
more recent literature.
A study in the U.K.
cognitive variables (benefits, barriers, fears, and fatalism)
eliminated differences by socioeconomic status in intention
for colorectal cancer screening, which supports our findings
in the United States. We know of no prior studies examin-
ing mediators that may be manipulated to encourage low-
income women with insurance to get screened.
Strengths of the study include a population-based sample
because it included a random sample of the entire popula-
tion of enrollees in a managed care plan as well as individ-
ual-level data on women’s perceptions, attitudes, and beliefs.
Additionally, longitudinal data were used to test associations
prospectively, which is important for designing interven-
tions, as prospective data have been shown to serve as a
richer set of predictors of future behavior than cross-sectional
Conducting the study in an integrated health plan en-
abled an examination of barriers beyond cost. The study was
conducted in a closed healthcare setting where the outcome
could be ascertained through administrative files, eliminat-
ing recall bias and overestimation of the outcome commonly
found when using self-reported data.
The results of this study should be used to inform future
mammography interventions, especially efforts to reach low-
income women in managed care settings. Recent work
gests that even today lower income women are under-
screened, so increasing mammography use in low-income
populations may be an important step to addressing socioe-
conomic disparities in breast cancer mortality. An efficacious
tailored approach to a woman’s past behavior that addresses
specific beliefs about the importance of mammography and
facilitates transportation to the appointment may also in-
crease use among all groups of women.
We extend our appreciation to Sue Curry, Ph.D., Evette
Ludman, Ph.D., and William Barlow, Ph.D., who helped de-
velop and conduct the original study.
No competing financial interests exist.
1. Edwards BK, Brown ML, Wingo PA, et al. Annual report to
the nation on the status of cancer, 1975–2002, featuring pop-
MAMMOGRAPHY USE AND INCOME 1377