Asthma

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Behavioral Risk Factor Surveillance System (BRFSS) Prevalence Data

Background Information

The Behavioral Risk Factor Surveillance System (BRFSS) is the world’s largest telephone survey. The BRFSS is a state-based, random-digit-dialed telephone survey of the noninstitutionalized civilian population 18 years of age and older. It is designed to monitor the prevalence of the major behavioral risks among adults associated with premature morbidity and mortality. Information from the survey is used to improve the health of the American people.

The BRFSS, which is administered and supported by Behavioral Surveillance Branch in the Division of Adult and Community Health, National Center for Chronic Disease Prevention and Health Promotion, at the Centers for Disease Control and Prevention, is an ongoing data collection program. By 1995, all states, the District of Columbia, and three territories were participating in the BRFSS. CDC develops standard core questionnaires for states to use to provide data that can be compared across states. States can choose to add additional questions of their own and can also choose among a number of optional modules that cover specific topics in greater detail. More information about BRFSS can be found at: http://www.cdc.gov/brfss/.

Before 1999, several states included questions about asthma on their BRFSS questionnaire, but the wording of the questions varied among those states. In 1999, an optional two-question adult asthma module was added to the BRFSS, representing the first effort to systematically collect state-based asthma prevalence data. In 2000, the two questions were included in the core of the BRFSS questionnaire and were asked in all participating states and territories. The two adult asthma prevalence questions will be included in the BRFSS in future years as well. Beginning with 2001, two questions on child prevalence are available.

For each year of BRFSS asthma data, two asthma prevalence measures were constructed. Lifetime asthma is defined as an affirmative response to the question “Have you ever been told by a doctor {nurse or other health professional} that you have asthma?”. Current asthma is defined as an affirmative response to that question followed by an affirmative response to the subsequent question “Do you still have asthma?” Responses to these two questions have been tabulated for adults for various demographic groups. Technical information important to understanding the tables and maps is also provided.

Responses to asthma related questions for children have been tabulated for those states that included the child asthma prevalence module. For BRFSS surveys from 2002 – 2004, lifetime asthma for children was defined in terms of the number of children that have ever been diagnosed with asthma. Childhood current asthma was defined as the number of children that still had asthma. From 2002 – 2004, the lifetime asthma in a household was determined from the response to the question “Earlier you said there were [fill in number] children age 17 or younger living in your household. How many of these children have ever been diagnosed with asthma?”. Current asthma in a household was determined from the response to the question “[“Does this child” or “How many of these children”] still have asthma?”.

Starting in 2005, both lifetime and current asthma for children are defined based on a randomly selected child from a household. If the interviewed adult reported that one or more children aged 17 years or younger lived in the household, then one of the children was randomly selected as the “Xth” child. Questions on the Childhood Asthma optional modules were then asked of the “Xth” child. The two questions pertinent to prevalence estimation of lifetime and current asthma are “Has a doctor, nurse or other health professional EVER said that the child has asthma?”, and “Does the child still have asthma?”. Since these questions pertain to a randomly selected child, the sample weighting scheme adopted from 2005 onwards for childhood asthma data is different to the scheme used prior to 2005. Specific details of weighting for each BRFSS year are given under technical information for that year.

In addition, responses to the Adult Asthma History module have been tabulated for states that included the adult history module. Technical documentation is provided for the Childhood Asthma module and Adult Asthma History module.