Notes for Data Users
2003 Data Limitations
The BRFSS is a cross-sectional surveillance survey currently involving 54
reporting areas (1). It is important to note that any survey will have
natural variation across sample sites; therefore, some variation between
states is to be expected. The complex sample design and the multiple
reporting areas complicate the analysis of the BRFSS. Although CDC works
with the states to minimize deviations, in 2003 there were some deviations
in sampling and weighting protocols, sample size, response rates, and
collection or processing procedures. In addition, California’s questionnaire
had a few minor differences in wording of questions. The following section
identifies other known variations for the 2003 data year.
A. 2003 Data Anomalies and Deviations from Sampling Frame and
In 75% of the states, a portion of sample records intended for use during
one month took more than one month to complete. In several instances, states
used their monthly sample over a period of several months. This deviation
will disproportionately affect analyses based on monthly, rather than
annual, data. Additionally, Michigan received its sample quarterly rather
Several states did not collect data for all 12 months of the year. New
Jersey did not report any interviews in July. The District of Columbia did
not complete any interviews in May, June, July, and August. New Mexico did
not complete any interviews in October and Ohio did not complete interviews
in July and August.
Several states were unable to close out the December sample in 2003 and
data collection continued into early 2004. Illinois, Kentucky, Nevada, New
Mexico, Ohio, Oklahoma, Utah, and Wisconsin had some completed interviews in
January, 2004. Hawaii completed some interviews in January and February,
More information about the quality of the survey data can be found in the
2003 BRFSS Summary Data Quality
B. Other Limitations of the 2003 Data
Telephone coverage varies by state and also by subpopulation. Telephone
coverage averages 97.6% for U.S. states as a whole, but noncoverage ranges
from 1.1% in Connecticut and New Hampshire, to 6.6% in Mississippi. It is
estimated that 23.8% of households in Puerto Rico are without telephone
service. Data on telephone coverage in U.S. households are available at
Illinois used a dual questionnaire and collected data on core items
addressing health status, health care access, exercise, diabetes,
hypertension and cholesterol awareness, asthma, immunization, tobacco use,
alcohol consumption, physical activity, and demographics from all eligible
respondents. Questions about fruit and vegetable consumption, weight
control, excess sun exposure, arthritis, falls, disability, veteran’s
status, and HIV/AIDS were asked of about half of eligible respondents.
California modified the wording of core questions addressing health
plans, diabetes, frequency of alcohol consumption, Hispanic ethnicity, level
of education, and household income. The data from these questions may
therefore have limited comparability to those of other reporting areas.
The data from an optional module is included if asked of all eligible
respondents within a state for the entire data collection year. A state may
have indicated the use of an optional module in 2003, but the data may have
been moved into the state-added questions if it does not represent all
A change in 2002 to the final disposition codes has continued to present
some inconsistencies in closing out the questionnaire. Prior to 2002,
interviews that were terminated during or after the demographics section
were coded as complete interviews, and any remaining unanswered questions
were coded as refused by the interviewer. In 2002, a revised procedure was
implemented for handling partial completes. The revised procedure for
partial completes is to stop coding questions at the point of interview
termination to assign the appropriate disposition code. However, states have
not consistently followed the procedure. During 2003, states generally
handled partial complete interviews in one of three ways: they 1) coded the
remaining questions as refused and coded the record a 110 Complete, 2) coded
the remaining questions as refused and coded the record a 120 Partial
Complete, or 3) did not ask the remaining questions (answers left as
missing) and coded the record a 120 Partial Complete. The variability in how
the interviews are dispositioned and where in the survey the interview was
terminated will have an impact on refusal rates for certain questions and
modules. These inconsistencies should be taken into account when determining
which records to include in an analysis. Records with a termination in the
questionnaire followed by coded refusals for the remainder of the eligible
responses have been dispositioned as 120 Partial Completes.
Another issue regarding partial completes is the inappropriate coding of
the remaining questions as “refused” (i.e., ‘9’) when some of these
questions may have valid response codes of greater than ‘9.’ For example,
some questions allow responses of 01-76, 77, 88, and 99 (with 99 as the
refusal code). The problem occurs when an interviewer incorrectly codes the
remaining questions as refused and enters a ‘9’ instead of a ‘99’ for these
question response types. Nine (9) is a valid response for these particular
questions and should not have been used to indicate refusal; doing so may
have altered which questions were coded as refused for the remainder of a
core section or module. When reviewing responses to a partial complete, data
users should therefore be aware that a core section or module that follows
the demographics section may contain questions incorrectly coded as refused
Several states continue to ask the Diabetes module questions directly
after the Diabetes questions in the core of the survey. In addition, several
states ask the Adult Asthma module questions after the asthma questions in
the core. Some states have also asked the Childhood Asthma module questions
in the demographics section of the core survey after question 6, (CHILDREN)
– number of children under age 18 in household.
More information about survey item non-response can be found in the
2003 BRFSS Summary Data Quality
Report and in the respective states’ Data Quality Reports.
New Calculated Variables and Risk Factors
Not all of the variables that appear on the public use data set are taken
directly from the state files. CDC prepares a set of SAS programs that are
used for end of year processing. These programs prepare the data for
analysis and add weighting, sample design, intermediate, calculated
variables, and risk factors to the data set. The following calculated
variables and risk factors, created for the user’s convenience, are examples
of results from this procedure:
||MODCAT_, VIGCAT_, PACAT, _RFHLTH, _RFNOPA, _RFHYPE4
The procedures for the variables vary in complexity; some only combine
codes, while others require sorting and combining selected codes from
multiple variables, which may result in the calculation of an intermediate
variable. For further details regarding the calculated variables and risk
factors, refer to the document entitled “Calculated Variables and Risk
Factors for the 2003 Behavioral Risk Factor Surveillance System,” available
from the 2003 Technical
Documents and Survey Data page.
The variables listed below are used in the BRFSS Prevalence Data and
SMART BRFSS tables available on this Web site.
||Question/risk factor description
||How is your general health?
||Health Status (Risk factor for fair or poor health)
||Do you have any kind of health care coverage?
||During the past month did you participate in any physical activities?
||Have you ever been told by a doctor that you have diabetes?
||Risk factor for having been told blood pressure was high
||Have you ever had your blood cholesterol checked?
||Have you had your blood cholesterol check in the past five years?
||At risk for having been told your cholesterol is high
||Risk factor for consumption of five servings of fruits and vegetables per day
||Risk factor for lifetime asthma prevalence
||Risk factor for current asthma prevalence
||Adults 65+ who have had a flu shot within the past year
||Adults 65+ who have ever had a pneumonia vaccination
||At risk for smoking-related illnesses (current smoker)
||Four level smoking status
||Risk factor for respondents having had at least on drink of alcohol in the past 30 days
||Binge drinking where binge drinking is defined as having five or more drinks on one occasion
||Risk factor for heavy drinking
||Weight classifications based on BMI
||At risk for health problems related to being overweight (based on body mass index)
||Are you limited in any way in any activities because of physical, mental, or emotional problems?
||Do you now have any health problems that require you to use special equipment?
||Risk factor for meeting guidelines for moderate physical activity
||Risk factor for meeting guidelines for vigorous physical activity
||The variables below are included in the Prevalence tables, but are not included in the SMART BRFSS tables.
||What is your age (imputed for unknown/missing)?
||What is your race/ethnicity?
||What is your marital status?
||How many children live in your household?
||What is the highest grade or year of school you completed?
||What is your employment status?
||What is your annual household income?
||Gender of respondent