SMART: Selected Metropolitan/Micropolitan Area Risk Trends
Frequently Asked Questions (FAQs) for SMART BRFSS
For more information on BRFSS in general, see the
BRFSS FAQs. Also see the
BRFSS Maps Methods and FAQs for more information on the mapping
application.
What does “MMSA” mean?
The acronym “MMSA” refers to metropolitan statistical areas, micropolitan
statistical areas, and metropolitan divisions. These geographic subdivisions
are designated by the U. S. Office of Management and Budget and used by the
U. S. Census Bureau as of June 2003.
- Metropolitan statistical area — Group of counties that contain
at least one urbanized area of 50,000 or more inhabitants (e.g.,
Atlanta-Sandy Springs-Marietta, GA)
- Micropolitan statistical area — Group of counties that contain
at least one urban cluster of at least 10,000 but less than 50,000
inhabitants (e.g., Willimantic, CT)
- Metropolitan division — A smaller group of counties within a
metropolitan statistical area of 2.5 million or more inhabitants (e.g.,
Boston-Quincy, MA within Boston-Cambridge-Quincy, MA-NH Metropolitan
Statistical Area)
How were the MMSAs selected? Why are different MMSAs
available for different years?
All MMSAs with at least 500 completed interviews in the BRFSS data were
selected for inclusion in this project. The MMSAs included in the project
are those that met these criteria for a given year. Some MMSAs, especially
micropolitan areas, may not be able to attain a large enough sample size to
be included every year.
Why were MMSAs chosen rather than another type of local
jurisdiction?
MMSAs were chosen because they represent geographic areas that meet
standard definitions established by the U. S. Office of Management and
Budget, which are used by the Census Bureau and other federal, state, and
local governmental entities. MMSAs are composed of counties and the BRFSS
collects data about county of residence. This county information allows the
reporting of information by MMSAs. Analyzing data by another type of
jurisdiction, such as city or township, would require modification to the
BRFSS questionnaire.
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Why do some counties have data while others do not?
Certain counties within an MMSA have their own prevalence estimates
because they have enough respondents to generate weighted data sets. For
this analysis, weighting required at least 19 sample members in each of the
weighting classes, which are based on age, sex, and in some states, race.
Each state started with between 12 and 24 weighting classes, depending on
how the state post-stratified the data. Weighting allows the data to more
accurately reflect prevalence for the overall community. Please see the
SMART Technical Documents and Survey Data section for further
details.
Can MMSA and county data be grouped by categories such as race,
sex, and age?
No, the sample sizes are too small to allow subgroup or stratified
analyses.
Who developed the weighting process for the MMSA and county data?
What is the weighting methodology?
RTI International developed the weighting process. A short explanation
can be found under “Why do some counties have data while others do not?”
Please see the SMART Technical Documents and Survey Data section for
further details.
Can one MMSA’s prevalence estimates be compared with those of
another MMSA?
Yes. Because the same weighting methodology was used for all MMSAs,
you can compare prevalence estimates among MMSAs. Comparisons must be
interpreted with caution, however, since differences in estimates may be due
to demographic and/or socioeconomic differences between MMSAs. Also,
when comparing MMSAs, it is important to examine confidence intervals
(margin of error) to make sure that confidence intervals for closely-ranked
MMSAs do not overlap. For example, for 2002 diabetes diagnosis, Orlando is
5.5% (confidence interval 3.5% – 7.5%) and Tampa-St. Petersburg-Clearwater
is 7.0% (confidence interval 5.0% – 9.0%). These intervals overlap, so you
would not interpret the percentages as being different.
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Can these prevalence estimates be used to rank MMSAs?
Because data are available only for selected MMSAs, you have to
remember that ranking one MMSA as the “best” for a specific health risk only
means it is the best out of these selected MMSAs, not out of the entire
country. The “best” could also reflect sociodemographic differences in
populations within MMSAs (i.e., younger age group), or the way some MMSAs
are defined by the Office of Management and Budget (i.e., how wide of an
area around a city is considered part of the MMSA). Also, when comparing
MMSAs, it is important to examine confidence intervals to make sure that
confidence intervals for closely-ranked MMSAs do not overlap.
Why might these estimates differ from estimates that states have
calculated for local areas?
States may have used different boundaries — such as a city or township
rather than an MMSA or county — to calculate these earlier estimates. The
states would also have used a different weighting methodology. One advantage
of this project is that a common weighting system will allow for comparisons
across local jurisdictions and states.
Which risk factor categories are available for SMART BRFSS? Will
others be available in the future?
The risk factor categories available are alcohol consumption, asthma,
colorectal cancer screening, diabetes, exercise, health status, health care
access, nutrition, oral health, tobacco use, women’s health, and other risk
factors and calculated variables.
Do you plan to do this project every year? Would more MMSAs and
counties be available in the future?
Local level estimates are available only for 2002 at this time. Although
this was a one-time project, we hope this is the beginning of an ongoing
process in which local level data will be available for other years and for
other geographic subdivisions. The number of MMSAs and counties included
depends on sample size and the weighting procedure used.
Where can I obtain a copy of the BRFSS questionnaires?
The questionnaires are available in the
Questionnaires section of
the BRFSS Web site in portable document format (PDF). You will need Acrobat
Reader to view and print these documents.
I have other questions. Whom should I ask?
All questions should be directed to your BRFSS state coordinator.
Up-to-date contact information can be found on the
BRFSS State
Coordinator list.
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