Introduction
Indiana has participated in the
Behavioral Risk Factor Surveillance System (BRFSS) since its inception in 1984.
The Indiana State Department of Health (ISDH) conducts the BRFSS survey through
an annual cooperative agreement with the Centers for Disease Control and
Prevention (CDC). All 50 states and the District of Columbia participate in the
BRFSS.� 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.�
Over 400,000 adult interviews are
conducted each year for the BRFSS, making it the largest continuously conducted
health survey system in the world.� The
surveys are conducted on a continuous basis throughout the year to determine
the proportion of adults who engage in health behaviors that increase the
probability of both positive and negative health outcomes. These data are also
used to monitor progress toward Healthy People 2020 objectives.
In 2011, the BRFSS was enhanced by
including interviews via cell phone and introducing a new weighting methodology
� iterative proportional fitting (�raking�), which replaced post stratification
to weight the data.� The inclusion of
cellular-only/mostly households will improve survey coverage for certain
population groups, (e.g., younger
adults, those with lower education levels, or those with lower incomes) and
result in prevalence more representative of adults in each state and the
nation.�
Over the years, many ISDH public
health promotion initiatives 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.� In recent years, Indiana has obtained
information on the prevalence of prediabetes, cognitive decline, consumption of
sugar-sweetened beverages, and health care access surveyed among many other
variables.
Core questions, which are surveyed
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.
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 2016 was 11,066
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.
Interview Process and Quality Assurance
Measures
In 2016, the ISDH contracted with
Clearwater Research, Inc., for telephone interviewing, data preparation, and
data quality measures. A computer-assisted telephone interviewing system (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.
CDC mandates quality assurance of the
survey data. The quality of the data collected from respondents was
evaluated daily to assure proper completion. Unobtrusive monitoring of the
interviews and data entry was conducted to ensure adherence to protocols.� Call-backs were also 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 summarized the quality of the
2016 BRFSS survey data.� Response rates
for the BRFSS are calculated using standards set by the American Association of
Public Opinion Research (AAPOR).�
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 ascertaining which telephone numbers are
out-of-sample and which telephone numbers represent �likely households� much
more difficult than in past years.� In
those instances, 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 calculation of the response rate provided
below:
|
Overall
Response Rate (%) |
Indiana -Landline |
41.5 |
US Median-Landline |
47.7 |
Indiana �Cell Phone |
41.4 |
US Median � Cell Phone |
46.3 |
Indiana - Combined |
41.5 |
US Median - Combined |
47.1 |
������������������ Source:� 2016 Summary Data Quality Report, CDC
Survey Limitations
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 was considered statistically
unreliable.
Starting
with 2011, two changes in the method of the BRFSS were introduced:
�
The inclusion of cell phone interviews.� In 2011, approximately
30 percent of American homes had only cellular telephones.� In 2016, 50.5% of households had only cellular telephones (National Center
for Health Statistics).� 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 2016,
the core questionnaire and optional modules of the Indiana BRFSS survey were
asked on both the landline and cell phone versions of the survey.� In the tables, _LLCPWT is noted in the denominator
when the questions were asked of both landline and cell phone respondents.� ��
As a result of the inclusion of cell
phones and change in survey methodology, results from the 2011-2016 BRFSS are
not directly comparable to prior years.�������
National BRFSS Prevalence Summary
The CDC Behavioral Surveillance
Branch 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 2016 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 2016.