Methodologic changes in the Behavioral Risk Factor Surveillance System in 2011 and potential effects on prevalence estimates.

In the past few years, all large population health surveys that depend on telephone interviews, including the Behavioral Risk Factor Surveillance System (BRFSS), have had to adjust to the rapid rise in the proportion of U.S. households that have a cellular telephone but no landline telephone. To maintain survey coverage and validity, surveys have had to add cellular telephone households to their samples. In addition, telephone surveys have had to make adjustments in weighting to account for declining response rates by adopting new methods of weighting to adjust survey data for differences between the demographic characteristics of respondents and the target population. Since 2004, BRFSS has been planning and testing the addition of cellular telephone households and improvements in its methods of statistical weighting. These new methods were implemented during the fielding of the 2011 BRFSS, which is to be released in 2012. This policy note describes the methodologic changes and their potential effects on BRFSS prevalence estimates. Preliminary assessments indicate that the inclusion of cellular telephone respondents and the move to a new method of weighting might increase prevalence estimates for health risk behaviors and chronic disease in many states. Carefully planned communication to public health officials and nonscientific audiences of the effect of changes in methods on estimates is needed to prevent misinterpretation.