Persistent Area Socioeconomic Disparities in U.S.
Incidence of Cervical Cancer, Mortality, Stage, and
Gopal K. Singh, Ph.D.
Barry A. Miller, Dr.P.H.
Benjamin F. Hankey, Sc.D.
Brenda K. Edwards, Ph.D.
Surveillance Research Program, Division of Cancer
Control and Population Sciences, National Cancer
Institute, National Institutes of Health, Bethesda,
Address for reprints: Gopal K. Singh, Ph.D., Divi-
sion of Cancer Control and Population Sciences,
National Cancer Institute, 6116 Executive Boule-
vard, Suite504, MSC8316,
Received February 26, 2004; revision received
April 6, 2004; accepted June 1, 2004.
*This article is a U.S. government work and, as
such, is in the public domain in the United States
ethnic disparities in patient survival and stage at diagnosis in relation to socioeco-
nomic deprivation measures have not been well studied in the United States. The
current article analyzed temporal area socioeconomic inequalities in U.S. cervical
cancer incidence, mortality, stage, and survival.
METHODS. County and census tract poverty and education variables from the 1990
census were linked to U.S. mortality and Surveillance, Epidemiology, and End
Results cancer incidence data from 1975 to 2000. Age-adjusted incidence and
mortality rates and 5-year cause-specific survival rates were calculated for each
socioeconomic group and differences in rates were tested for statistical signifi-
cance at the 0.05 level.
RESULTS. Substantial area socioeconomic gradients in both incidence and mor-
tality were observed, with inequalities in cervical cancer persisting against a back-
drop of declining rates. Cervical cancer incidence and mortality rates increased
with increasing poverty and decreasing education levels for the total population as
well as for non-Hispanic white, black, American Indian, Asian/Pacific Islander, and
Hispanic women. Patients in lower socioeconomic census tracts had significantly
higher rates of late-stage cancer diagnosis and lower rates of cancer survival. Even
after controlling for stage, significant differences in survival remained. The 5-year
survival rate among women diagnosed with distant-stage cervical cancer was
approximately 30% lower in low than in high socioeconomic census tracts.
CONCLUSIONS. Census-based socioeconomic measures such as area poverty and
education levels could serve as important surveillance tools for monitoring tem-
poral trends in cancer-related health inequalities and targeting interventions.
Cancer 2004;101:1051–7. Published 2004 by the American Cancer Society.*
Temporal cervical cancer incidence and mortality patterns and
KEYWORDS: Surveillance, Epidemiology and End Results program, cervical cancer,
incidence, mortality, stage, survival, poverty, deprivation, socioeconomic status,
tus (SES).1,2Although several studies have examined cross-sectional
patterns,3–10temporal cervical cancer incidence and mortality pat-
terns in relation to socioeconomic deprivation measures, especially at
the national level, have been less well studied.11The analysis of
socioeconomic and ethnic patterns in stage-specific survival for cer-
vical cancer at the national level has also not received much atten-
tion.12–14Documenting such patterns is an important surveillance
activity, both in terms of quantifying cancer-related health disparities
between the least and most advantaged socioeconomic groups and
ontemporary data indicate that higher cervical cancer incidence
and mortality rates are associated with lower socioeconomic sta-
Published 2004 by the American Cancer Society*
Published online 26 July 2004 in Wiley InterScience (www.interscience.wiley.com).
for identifying population groups or areas that are at
greatest risk of cancer morbidity, mortality, and poor
survival and that may therefore benefit from focused
social and medical interventions. Such analyses may
also provide insights into the impact of cancer control
interventions, such as screening for cervical car-
Individual-level socioeconomic data are not avail-
able for patients with cancer in the National Cancer
Institute’s Surveillance, Epidemiology, and End Re-
sults (SEER) database.15Reliable socioeconomic data
are also lacking in national mortality databases.16,17
Therefore, in the current study, we link two census-
based area measures, the poverty rate and the per-
centage of population with at least a high school di-
ploma, to the U.S. mortality data using the county of
residence of the decedent and to the incidence data
from 11 population-based SEER cancer registries us-
ing the county and census tract residence of the pa-
tient with cancer at the time of diagnosis.15–18This
linkage allows us to examine temporal socioeconomic
patterns in cervical cancer incidence and mortality
and recent cross-sectional socioeconomic patterns in
incidence, mortality, stage, and survival for the total
population and for major racial/ethnic groups.
MATERIALS AND METHODS
The poverty rate is defined as the percentage of pop-
ulation in a county or census tract below the poverty
level, a threshold that varies by family size and com-
position ($12,674 for a family of 4 in 1990).18Poverty
rate is a measure of economic deprivation and corre-
lates highly with other SES measures, such as educa-
tional attainment, unemployment rate, and occupa-
tional composition.11Three categories of poverty rate
in 1990 were used to classify areas: ? 10% (low pov-
erty), 10–19.99% (middle poverty), ? 20% (high pov-
erty). The other SES measure used was the percentage
of county or census tract population aged ? 25 years
with at least a high school diploma in 1990.18Three
categories of education (based on quintile distribution
of the U.S. population) were used to classify areas:
? 69.69% (first quintile), 69.69–82.02% (second
through fourth quintiles), and ? 82.02% (fifth quin-
tile). The first and fifth education quintiles represent
low and high SES groups, respectively.
Because the national mortality database lacks the
census tract geocode, temporal and cross-sectional
analyses of mortality data involved the use of county
poverty and education measures.16The SEER data-
base contains the county geocode from 1975 to 2000
and the census tract geocode from 1988 to 2000.15The
incidence trend analyses from 1975 to 2000 involved
the use of county socioeconomic variables. However,
for cross-sectional patterns in incidence during 1988–
1992 and for stage and survival analyses, the census
tract socioeconomic variables were used.
Incidence and mortality rates for each socioeco-
nomic group were age adjusted by the direct method
using the age composition of the 2000 U.S. standard
population and 5-year age-specific incidence and
mortality rates.11,15Five-year cause-specific survival
rates were computed by treating patients dying of
causes other than cervical cancer as censored obser-
vations.11,19Differences in rates were tested for statis-
tical significance at the 0.05 level.
Figure 1 presents temporal socioeconomic patterns in
SEER incidence and U.S. mortality rates from 1975 to
2000. Although U.S. cervical cancer mortality rates
decreased consistently for all area poverty groups be-
tween 1975 and 2000, the socioeconomic gradients in
mortality did not diminish during this period (Fig. 1B).
Rather, the gradient (the ratio of mortality rates for
high and low poverty counties) appeared to have in-
creased slightly, from 1.62 (95% confidence interval
[CI] ? 1.49–1.75) in 1975 to 1.83 (95% CI ? 1.66–2.00)
in 2000. This is primarily because of a faster rate of
mortality decline for low poverty areas than for high
poverty areas. The average annual exponential rates of
mortality decline for low, medium, and high poverty
counties were 2.55% (95% CI ? 2.32–2.77%), 2.28%
(95% CI ? 2.06–2.49%), and 1.88% (95% CI ? 1.60–
2.16%), respectively. Temporal patterns in mortality
by county education were almost identical to those for
poverty (Fig. 1D). The average annual rates of mortal-
ity decline for low, medium, and high education coun-
ties were 2.02% (95% CI ? 1.76–2.27%), 2.32% (95% CI
? 2.11–2.52%), and 2.61% (95% CI ? 2.36–2.86%),
The SEER cervical cancer incidence rates also
showed a downward trend for all county poverty
groups during 1975–2000 (Fig. 1A). However, a sub-
stantial gradient remained, with women in high pov-
erty counties having at least a one-third higher inci-
dence rate than those in low poverty counties
throughout the study period. The socioeconomic gra-
dients in incidence (the ratio of incidence rates for
high and low poverty counties) appeared to have de-
creased somewhat over time, from 1.77 (95% CI
? 1.55–1.99) in 1975–1977 to 1.37 (95% CI ? 1.18–1.55)
in 1998–2000. Although the average annual decreases
for high poverty counties were similar for incidence
and mortality trends, the rate of decrease for low pov-
erty counties was greater for mortality than for inci-
dence trend. The average annual exponential rates of
decline in incidence for low, medium, and high pov-
1052CANCER September 1, 2004 / Volume 101 / Number 5
erty counties were 1.30% (95% CI ? 1.06–1.54%),
2.05% (95% CI ? 1.70–2.40%), and 2.10% (95% CI
? 1.86–2.34%), respectively. Similar temporal patterns
can be noted by county education (Fig. 1C), with an-
nual rates of decline in incidence for low, medium,
and high education counties being 2.10% (95% CI
? 1.88–2.33%), 1.61% (95% CI ? 1.35–1.87%), and
1.47% (95% CI ? 1.16–1.77%), respectively.
U.S. cervical cancer mortality generally increased
with increasing poverty and decreasing education lev-
els for women in all racial/ethnic groups (Fig. 2B,D).
During 1996–2000, American Indian women in low
SES counties had more than twice the mortality of
their counterparts in high SES counties. The rates
were, respectively, 46% (95% CI ? 37–55%), 49% (95%
CI ? 34–63%), and 82% (95% CI ? 51–113%) higher
for non-Hispanic white, black, and Hispanic women
in high than in low poverty counties. The mortality
rates were, respectively, 62% (95% CI ? 53–72%), 74%
(95% CI ? 53–96%), and 49% (95% CI ? 20–77%)
higher for non-Hispanic white, black, and Hispanic
women in low than in high education counties.
The higher the census tract SES, the lower the
cervical cancer incidence during 1988–1992 (Fig.
2A,C). Compared with the rates for their counterparts
in low poverty census tracts, the incidence rates for
FIGURE 1. Trends in Surveillance, Epidemiology, and End Results (SEER) cervical cancer incidence and U.S. cervical cancer mortality rates by county
socioeconomic measures, 1975–2000. Rates are age adjusted to the 2000 U.S. standard population. Incidence trend data are based on nine SEER registries that
include the states of Connecticut, Hawaii, Iowa, New Mexico, and Utah, as well as the metropolitan areas of Atlanta, Detroit, San Francisco and Oakland, and Seattle.
Socioeconomic Disparities in U.S. Cervical Cancer/Singh et al.1053
non-Hispanic white, black, American Indian, Asian
Pacific Islander, and Hispanic women were, respec-
tively, 97% (95% CI ? 80–114%), 30% (95% CI ? 12–
49%), 292% (95% CI ? 31–615%), 44% (95% CI ? 17–
71%), and 83% (95% CI ? 62–105%) higher in high
poverty census tracts. Patterns by education were sim-
ilar, with the incidence rates being almost two times
higher for non-Hispanic whites and Hispanics and
four times higher for American Indians in low than in
high education census tracts.
Women were 20% (95% CI ? 1.00–1.40%) more
likely to be diagnosed with a distant-stage cervical
cancer in high than in low poverty census tracts, with
the impact of poverty on late-stage diagnosis being
most pronounced for Hispanics (Fig. 3A). Educational
gradients in distant-stage cervical cancer diagnoses
were less consistent, although educational patterns in
localized and regional-stage cancers were similar to
those for poverty (Fig. 3B). Among women diagnosed
with invasive cervical cancer between 1988 and 1994,
the 5-year survival rates were 79.1% (95% CI ? 78.0–
80.2%), 75.6% (95% CI ? 73.9–77.2%), and 72.6% (95%
CI ? 70.9–74.3%) in low, medium, and high poverty
census tracts, respectively. The 5-year survival rates
were 73.1% (95% CI ? 70.2–76.0%), 76.6% (95% CI
? 73.5–79.6%), and 80.3% (95% CI ? 77.2–82.2%) in
FIGURE 2. Recent cross-sectional socioeconomic patterns in Surveillance, Epidemiology, and End Results (SEER) cervical cancer incidence and U.S. cervical
cancer mortality rates, 1988–2000. Rates are age adjusted according to the 2000 U.S. standard population. Cross-sectional patterns in incidence rates are based
on 11 SEER registries that included the states of Connecticut, Hawaii, Iowa, New Mexico, and Utah, as well as the metropolitan areas of Atlanta, Detroit, Los Angeles,
San Francisco and Oakland, San Jose and Monterey, and Seattle. Mortality rates for Hispanics and non-Hispanic whites are based on 1997–2000 data.
1054 CANCER September 1, 2004 / Volume 101 / Number 5
low, medium, and high education census tracts, re-
spectively. Even after controlling for stage, signifi-
cant differences remained (Fig. 4). For example,
among women diagnosed with distant-stage cervi-
cal cancer, the 5-year survival rate was 31% (95% CI
? 18.1–43.4%) lower in high than in low poverty
census tracts and 30% (95% CI ? 17.2–42.2%) lower
in low than in high education census tracts.
By analyzing population-based SEER incidence and
U.S. mortality data, the current study has shown
substantial socioeconomic disparities in cervical
cancer, which have persisted over time against a
backdrop of declining incidence and mortality rates.
The significant association between lower SES and
higher incidence and mortality rates and lower like-
lihoods of survival and early-stage diagnoses was
generally observed for each racial/ethnic group, al-
though the magnitude of the association varied by
ethnicity. These patterns are consistent with the
We used only three broad socioeconomic cate-
gories for a simpler presentation of data and for
minimizing potential misclassification of areas over
time, but the impact of poverty and education on
cervical cancer may be graded across the entire
range of the social hierarchy.7,11The 1980 poverty
and education variables are more likely than the
corresponding 1990 variables to accurately charac-
terize the socioeconomic characteristics of counties
during 1975–1984 due to its temporal proximity.
However, because the 1980 and 1990 county socio-
economic variables were highly correlated (? ? 0.91
[poverty] and 0.94 [education] for the United States;
? ? 0.90 [poverty] and 0.82 [education] for the SEER
FIGURE 3. Distribution of cervical cancer cases by stage at diagnosis, race/ethnicity, and census tract socioeconomic measures, 1995–1999. Rates are based
on data from 11 Surveillance, Epidemiology, and End Results (SEER) registries. Stage data were not available for the Los Angeles registry from 1988 to 1991.
Socioeconomic Disparities in U.S. Cervical Cancer/Singh et al.1055
region), the cervical cancer incidence and mortality
trends based on the 1980 SES variables were essen-
tially similar to those based on the 1990 variables
(data not shown), suggesting very little, if any, mis-
classification of areas over time.
Our findings may be affected by possible ethnic
misclassification in patient medical records and
death certificates and by any incorrect geocoding of
patients to specific census tracts.25–29Results could
also be biased if the socioeconomic category asso-
ciated with residence at the time of diagnosis or
death differed from that at exposure. Despite these
potential limitations, census-based area measures,
e.g., poverty and education levels, can serve as im-
portant surveillance tools for monitoring temporal
trends in cancer-related health inequalities, as well
as in cancer control planning and health resource
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