METHODS
Data from the 2009 Behavioral Risk Factor Surveillance System (BRFSS) were used [49]. The BRFSS is an annual, state-based, random-digit-dialed telephone interview survey of adults aged ≥18 years from all over the United States. It is conducted by the Centers for Disease Control and Prevention and it is designed to monitor health-related behaviors in the general population. For the present analyses, data from 6 states were included, representing states from the West (Hawaii and Wyoming), South (Georgia and Louisiana), and Midwest (Illinois and Minnesota); no states from the Northeast provided data. Response rates ranged from 45.6% (Hawaii) to 59.7% (Minnesota), and cooperation rates ranged from 68.9% (Hawaii) to 83.9% (Georgia)[50].
All analyses are adjusted to remove bias in the sample. To do this, BRFSS assigns a weight to each participant to account for differences in selection probability, lack of coverage or response, number of residential telephone lines in the home of each participant, and number of adults in the household. This increases generalizability of results by accounting for factors of location and accessibility, and characteristics such as age, sex, and ethnicity. A more detailed description can be located within BRFSS documentation