Health services research often utilizes secondary data
sources such as the Behavioral Risk Factor Surveillance
System (BRFSS). Since 2006, the released BRFSS data do
not include respondents who live in counties with 10,000
or fewer residents, and the CDC no longer offers the
opportunity to access the unrestricted data set. As a
result, rural residents can be underrepresented in BRFSS
data after 2005. The purpose of this analysis is to
examine the potential for bias introduced by rural
We utilized 6 BRFSS data sets; the 2005 full data and the
2005-2009 restricted data. We estimated population sizes
for each survey year, and we compared these estimates to
comparable data from the US Census intercensal estimates.
We also compared estimates of preventive service
utilization (mammography, Pap tests, colorectal cancer
screening, and influenza vaccinations) between the two
2005 data versions.
Rural populations were underrepresented, particularly
with the smaller counties excluded. Remote rural
residents were the most consistently underrepresented.
Preventive service delivery estimates differed between
the full and restricted 2005 data versions. Mammography
and Pap test estimates tended to be higher in the
restricted data, while colorectal cancer screening and
influenza vaccinations were similar or inconsistent.
These results indicate that restricting by county size
introduced bias in these estimates.
Having quality, nationally representative data is
important to study disparities in service delivery. The
potential bias introduced by the BRFSS county restriction
may result in rural research being less effective for
policy recommendations and interventions.