Methodologic Changes in the Behavioral Risk Factor Surveillance System in 2011 and Potential Effects on Prevalence Estimates

Refinements to the Behavioral Risk Factor Surveillance System (BRFSS) to include data received from cell phone users facilitates the inclusion of a broader demographic and ultimately provides a better reflection of the nation’s health status.

The BRFSS telephone survey has been traditionally done with people using land lines. However, in recent years, an increasing number of people are only using cell/mobile phones. CDC recognized the need to include cell phone users in our survey in order to obtain data that better represents the diverse populations in our society (nation). Because we have expanded and improved the way we gather and process information, new data cannot be accurately compared to previous findings line by line (point by point). However, as we move forward, the survey results will better reflect the health status of the people of the United States.

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 respond to the rapid rise in the proportion of U.S. households that contain only cellular telephones and no landline telephones. In order to maintain survey coverage and validity, surveys have had to add cellular telephones to their samples. At the same time, new methods of weighting to adjust survey data for differences between the demographic characteristics of respondents and the target population have been adopted. Since 2004, the BRFSS has been planning and testing the addition of cellular telephones and improvements in its method 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 methodological changes and their potential effects on BRFSS prevalence estimates. Policy makers who use BRFSS estimates for decision making should be aware of the new methods and their potential effects on estimates. Careful planning in communicating the impact of changes in methods on estimates to non-scientific audiences is needed to prevent misinterpretation.