9 Behavioral Risk Factor Surveillance System
9.1 Introduction
Chapter 9 covers the Behavioral Risk Factor Surveillance System (BRFSS). The BRFSS has been conducted by the Centers for Disease Control and Prevention (CDC) since 1984 to collect data on health behaviors, physical activity, diet, hypertension and preventive safety measures (e.g. seat-belt use) among US adults.1 This chapter includes details on: how data are collected; how data are made publicly available as machine-actionable data files; what variables must be included to address design features of the complex sample; the strengths and limitations of the survey; and practical tips for conducting statistical analysis; and how to answer research questions using a case study. The practical tips provided for analysis of BRFSS data are based on the primary author’s previous experiences analyzing 2014 and 2019 BRFSS data to answer questions related to associations between predisposing and enabling factors that contribute to morbidity, mortality and health services use. The BRFSS case study will explore how differences in caregiving experiences among urban and rural adults in Texas are moderated by race and ethnicity. The bulk of this chapter will comprise of section 9.6: Case Study in order to give investigators hands-on practice downloading and cleaning large databases and conducting basic categorical data analysis using PROC SURVEYFREQ and PROC SURVEYLOGISTIC. The syntax provided was created for use with SAS 9.4.
9.2 Data Collection
Since beginning in 1984, the BRFSS was expanded in 1988 to include optional modules, including chronic disease, health care access, and preventive services uptake. Some optional modules include data collection among children.1 In 1993, the BRFSS was further expanded to become an annual national surveillance system. The BRFSS uses a random-digit-dialing cross-sectional study design to collect data using a computer-assisted telephone interview (CATI) system. The BRFSS is one of the largest health surveys collected worldwide with over 400,000 responses collected each year.2 Prior to 2008, data were only collected from landline telephones. In 2008, the methodology was revised to conduct interviews using cell phones. Response rates are calculated for landline, cell phone, and combined responses for each state. National response rates are calculated as a median of response rates from each state. In 2019, the overall national combined response rate was 49.4% (range from (37.3%-73.1%).3 Response rates were lowest in New York (39.5% landline, 33.5% cell phone, 37.3% overall) and highest in South Dakota (78.0% landline, 33.5% cell phone, 73.1% overall). For Texas, the landline response rate was 50.6%, the cell phone response rate was 37.6%, and the combined response rate was 46.3%.3 Further details of the BRFSS sampling design and data collection methods are reported on the BRFSS website.4
9.3 Data Files
The CDC provides a complete BRFSS public-use data file available a