Introduction
Indiana
has participated in the Behavioral Risk Factor Surveillance System (BRFSS) since
its inception in 1984. 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.
There
are over 400,000 adult interviews each year in 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 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. In recent years, Indiana has obtained
information on the prevalence of prediabetes, cognitive decline, consumption of
sugar-sweetened beverages, and health care access.
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.
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 2015 was 6,067 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
2015, the Indiana State Department of Health contracted with Clearwater
Research, Inc., for telephone interviewing and data preparation. 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.
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.
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 2015 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 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 calculation of the response rate provided
below:
|
Overall
Response Rate (%) |
Indiana
-Landline |
42.8 |
US
Median-Landline |
48.2 |
Indiana
–Cell Phone |
41.5 |
US
Median – Cell Phone |
47.2 |
Indiana
- Combined |
42.6 |
US
Median - Combined |
47.2 |
Source: 2015 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 were 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 2015, 45% 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
2015, 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 2011-2015 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 2015 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
2015.