Introduction
Indiana has the distinction of being
a pioneer among the states participating in the Behavioral Risk Factor
Surveillance System (BRFSS). Over the past few decades, many of the public
health promotion initiatives of the Indiana State Department of Health (ISDH)
have focused not only on infectious diseases and their prevention, but also on
chronic disease prevention and how certain behavioral risks are associated with
these diseases.
Since 1984, the ISDH has entered
into a yearly cooperative agreement with the Centers for Disease Control and
Prevention (CDC) to develop and implement the BRFSS survey in Indiana. This
national telephone-based survey monitors modifiable risk factors associated
with chronic and communicable diseases by collecting information from adults on
their health behaviors and preventive practices. Since the early years,
continuous improvement in the collection process and analysis of the data has
provided public health professionals with a wealth of information that has
aided in promoting healthy lifestyles.
Health risk factors of adults, many
of which are behavioral in nature, are examined in the BRFSS. The surveys are
conducted on a continuous basis throughout the year to determine the proportion
of Indiana residents who engage in health behaviors that increase the
probability of both positive and negative health outcomes. These behavioral
risk factor prevalence data play a vital role in developing public policy and
monitoring achievement of public health goals.
The BRFSS is the largest
continuously conducted health survey in the world. It was developed by the CDC
to collect data on major behavioral risk factors that contribute to premature
death and disability. Emerging health concerns and other critical health issues
are also included in the survey. With this elaborate surveillance system,
the BRFSS monitors health behaviors in all states, the District of Columbia,
and U.S. territories, which permits state and regional comparisons, as well as
trend analyses.
Core questions, which are used by
all participating states each year, are developed jointly by the CDC and the
participating states. Standard modules on specific topics may be added to
accommodate the states' individual surveillance needs. States may also add
questions designed to gather data on local or regional needs.
Over the years, Indiana's BRFSS
program has increased surveillance coverage in the following areas: assessment
of general health status, use of health care resources, the prevalence of
selected chronic conditions, knowledge and awareness of AIDS and HIV, awareness
and prevalence of clinical screening procedures, vaccination uptake, and injury
issues.
Additional surveillance efforts of
the BRFSS program in Indiana have doubled the statewide sample size since the
first survey was done, expanded the use of rotating modules specific to program
areas within the ISDH, increased the number of state-added questions, and aided
several counties with the development of their own surveys to monitor health risk
factors in specific geographic areas.
Goals and Objectives of the BRFSS
The ISDH, in partnership with a
variety of public and private programs, is responsible for planning,
implementing, evaluating, and tracking disease and injury prevention programs
in Indiana. The ultimate goal of the national BRFSS survey is to provide valid
data to assist in these tasks. To help states achieve these goals, the CDC has
established the following objectives for all BRFSS programs:
· Determine
prevalence of personal health behaviors associated with the leading causes of
premature death.
· Increase
public awareness of lifestyles that can significantly influence health and
well-being.
· Monitor
behavioral risk factors over time and focus on factors that are not improving.
· Assess progress in meeting the
national health objectives for health promotion and disease prevention.
· Assess
the impact of state legislation on behavioral risks.
· Share BRFSS data with state and
local agencies involved with health-related issues.
The BRFSS questionnaire has three
basic parts: 1) a set of core questions used by all participating states and
U.S. territories, 2) standard modules on selected topics that may rotate from
year to year, and 3) state-added questions, which are developed by individual
states and relate to state and local health issues. The core and standard
modules are jointly developed by the states and the CDC. Because all
participants use the same core questions, data can be used for comparative
purposes and trend analyses.
Core health-related topics include:
health status, health care access, awareness of selected medical conditions
(hypertension, diabetes, and high cholesterol), injury control, tobacco and
alcohol use, women's health issues, the use of certain preventive health
measures, awareness and attitudes concerning HIV/AIDS, and prevalence of
testing for HIV infection. In addition to questions concerning health-related
behaviors, respondents were asked to provide demographic information such as
age, sex, race, marital status, household income, employment status, and
education level.
Standard modules assess such risk
factors as weight control, oral health, participation in leisure time and
physical activities, consumption of fruits and vegetables, consumption of
alcohol, and the use of smokeless tobacco.
Indiana's sample size for 2011 was 8,495
randomly selected Indiana residents aged 18 years or older. A disproportionate
stratified random sample design was used to generate the sample of telephone
numbers. In this design, information obtained from previous surveys was used to
classify 100-number blocks of telephone numbers into strata that were either
likely or unlikely to yield residential numbers. Telephone numbers in the
likely stratum were sampled at a higher rate than numbers in the unlikely
stratum.
A sample was drawn independently by
randomly sampling the telephone numbers within each stratum. Then, when an
interviewer called a sampled household, one adult living in the household was
randomly selected to be the respondent. The completed survey sample was
designed to produce a representative sample of all adult Indiana residents.
The Interview Process and Quality Assurance
Measures
In 2011, the Indiana State
Department of Health contracted with Clearwater Research, Inc., for telephone
interviewing and data preparation. A computer-assisted interviewing system
(CASS-CATI) was used in the interview process. A CDC-developed protocol was
followed to process the data. When monthly interviewing was completed, the data
were summarized utilizing a computer program provided by CDC. The summary and
the data were then submitted to CDC whose staff edited, corrected, compiled,
and weighted the state data into an annual file that was provided to the BRFSS
Program Coordinator at the ISDH.
Quality assurance of the survey data
is mandated by CDC. The quality of the data collected from respondents
was evaluated daily to assure proper completion. Call-backs were done randomly,
on a spot-check basis, to confirm that interviews had been conducted as
indicated.
The objective of the CDC data
quality protocol is to provide the most accurate data possible. Because
non-responses tend to bias the results of a survey, special attention was given
to minimizing the non-response rate. The extent to which completed interviews
were obtained from among all phone numbers selected is indicated by several
different measures of response rate. A high response rate indicates a lower
potential for bias in the data.
CDC summarizes the quality of the
2011 BRFSS survey data. Response rates,
cooperation rates, and refusal rates for BRFSS are calculated using standards
set by the American Association of Public Opinion Research (AAPOR). The AAPOR Response Rate#4 is used, which is consistent
with the rates provided by BRFSS in the past using Council of American Survey
Research Organizations (CASRO) rates.
AAPOR Response Rate -
These
calculations include assumptions of eligibility among potential
respondents/households that are not interviewed. Changes in the distribution of cell phone
numbers by telephone companies and the portability of landline telephone
numbers are likely to make it extremely more difficult than in the past to
ascertain which telephone numbers are out-of-sample
and which telephone numbers represent “likely households.” There, the BRFSS uses proportions of unknown
households in each of the states to estimate the total number of households
from those whose eligibility is undetermined.
This “eligibility factor” appears in calculations of response,
cooperation, and refusal rates provided below:
|
|
AAPOR
Cooperation Rate #4 (%) |
AAPOR
Refusal Rate #2 (%) |
Overall
Response Rate (%) |
AAPOR
Response Rate #4 (%) |
|
Indiana -Landline |
67.26 |
23.18 |
29.02 |
47.61 |
|
US Median-Landline |
76.96 |
15.99 |
32.94 |
52.98 |
|
Indiana –Cell Phone |
57.06 |
18.01 |
Not
applicable |
23.93 |
|
US Median – Cell Phone |
76.58 |
9.39 |
Not
applicable |
27.87 |
Source: 2011 Summary Data Quality Report, CDC
The BRFSS survey relies on
self-reported data and has certain limitations. These limitations should be
understood in the interpretation of the data. Many times, respondents have the
tendency to underreport some behaviors that may be considered socially
unacceptable, unhealthy, or even illegal such as high alcohol consumption,
drinking and driving, or not using seat belts. Conversely, respondents may
overreport behaviors that are considered desirable (the amount of exercise, low
body weight, or regular health screenings). Some information is also affected
by the ability of the respondent to recall past behaviors and respond
accordingly. The validity of survey results depends on the accuracy of the responses
to the survey questions from recalled past behaviors.
The BRFSS survey excludes households
without telephones, which may result in a biased survey population due to
underrepresentation of certain segments of the population. Additionally,
breaking down the data into smaller categories decreases the sample size of the
original risk factor categories, thereby decreasing the ability to determine
statistically significant differences.
Finally, it should be noted that
weighting the data by age, race, and sex distribution was done in order to
correct for over- or underrepresentation of all groups. Prevalence based on
denominators of less than 50 respondents were considered statistically
unreliable.
Starting
with 2011, two changes in the method of the BRFSS were introduced:
·
The inclusion of cell phone interviews.
Approximately three in ten American homes have only cellular
telephones. The trend towards cell-only
households has been especially strong among younger adults and among persons in
racial and ethnic minority groups.
·
Introduction of a new “weighting” procedure.
BRFSS responses are weighted to account for differences between
respondents and the target population – adults ages 18 years and older not
living in institutional settings.
Compared to the “post stratification” weighting method used by BRFSS for
more than two decades, the new method, iterative proportional fitting
(nicknamed “raking”), improves the accuracy of the BRFSS by allowing the use of
more demographic variables and interview type (landline or cell phone) in the
weighting.
In 2011,
the core questionnaire portion of the Indiana BRFSS survey was asked on both
landline and cell phone, while the modules were asked only on landline. In the tables, _LLCPWT is noted in the
denominator when the questions were asked of both landline and cell phone
respondents, and _LANDWT is noted when the questions were asked of only
landline respondents. By 2013, all
questions will be asked of landline and cell phone respondents for the Indiana
BRFSS survey.
As a result of the inclusion of cell
phones and change in survey methodology, results from the 2011 BRFSS are not
directly comparable to prior years.
The National BRFSS Prevalence Summary
The Behavioral Surveillance Branch
of the CDC provides a BRFSS summary prevalence report on selected risk factors
and preventive health measures from its survey for each participating state.
This summary report consists of tables capturing data provided by each
participating state indicating whether individual states are at, above, or
below the national median prevalence value.
The summary also provides a tool to
determine how states compare with each other and to the Healthy People 2020
objectives related to the risk factors that BRFSS measures. Summary
information includes the name of the participating state, the sample size, the
prevalence of the risk behavior, and the confidence interval for the prevalence
figure. An additional table was
developed using information from the 2011 BRFSS Prevalence Summary. It
includes information for the 50 states and the District of Columbia for a
selected number of risk factors. For each measure shown, a rank of 1 indicates
the negative end of the ranking. For all measures, a low percentage indicates
the desired prevalence.
A further comparison of risk factors
to national objectives is provided in Appendix A. These tables compare Indiana risk factor prevalence from
BRFSS data with national objectives and national BRFSS prevalence for those
behaviors for which Healthy People 2020 have explicitly stated
objectives and that were measured in Indiana in 2011.