SMART: BRFSS Frequently Asked Questions (FAQs)
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. The general concept of a metropolitan or micropolitan statistical area is that of a core area containing a substantial population nucleus, together with adjacent communities and all having a high degree of economic and social integration.
- 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
The U.S. Census Bureau Web site has more information on MMSAs.
How were the MMSAs selected? Why are different MMSAs available for different years?
MMSAs with at least 500 completed interviews in the BRFSS data were selected for inclusion in this project. The MMSAs included in the project met certain weighting 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.
If an MMSA only includes one county, why might the MMSA have a different name than the county? How do MMSAs get their names?
Some MMSAs only include one county. For instance, the Los-Angeles-Long Beach-Glendale, CA Metropolitan Division only includes Los Angeles County. If there is only one county in an MMSA, the MMSA and county have identical data sets. The largest city in each metropolitan or micropolitan statistical area is designated a "principal city." Additional cities qualify if specified requirements are met concerning population size and employment. The title of each metropolitan or micropolitan statistical area consists of the names of up to three of its principal cities and the name of each state into which the metropolitan or micropolitan statistical area extends. Titles of metropolitan divisions also typically are based on principal city names but in certain cases consist of county names.
Why do some counties have data while others do not? What is the weighting methodology?
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: BRFSS City and County Data and Documentation section for further details.
Why isn't my City/County represented on SMART BRFSS?
In order for an MMSA to be included in SMART BRFSS there must be at least 500 respondents within the MMSA and the weighting criteria must be applicable. In order for a county to be included, the county must be within a selected MMSA and the weighting criteria must be applicable at the county level. If you want to investigate the possibility of your city or county becoming eligible for inclusion in SMART BRFSS, please contact your state’s BRFSS Coordinator. You can find a list of BRFSS Coordinators, by state, in the BRFSS State Coordinators list.
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.
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.
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, cholesterol awareness, colorectal cancer screening, diabetes, disability, exercise and physical activity, health status, health care access, hypertension awareness, immunization, nutrition, oral health, tobacco use, weight classifications, and women’s health. The categories available will vary from year to year based on questionnaire changes.
Do you plan to do this project every year? Will more MMSAs and counties be available in the future?
This is an ongoing process in which local level data will be available for future years. The number of MMSAs and counties included depends on sample size and the weighting procedure used. Because states may change their sample size and design from year to year, the MMSAs and counties with data available for a given year will fluctuate.
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.
- Page last reviewed: July 12, 2013
- Page last updated: July 12, 2013
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