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R7 Analysis of BRFSS HRQOL Study

Principal Investigator: Willi Horner Johnson, PhD

The Behavioral Risk Factor Surveillance System (BRFSS) is an annual, state-based system of health surveys that generate information about health risk behaviors, clinical preventive practices, and health care access. Several questions on the BRFSS ask about Health Related Quality of Life (HRQOL). This study will examine the performance of the HRQOL questions among people with and without disabilities and how their prediction by other variables may inform development of improved health status measurement questions to assess health and well-being of individuals with disabilities regardless of functional status.

Hypothesis 1: There is adequate internal consistency among items of the BRFSS/HRQOL to yield a summary score.

Hypothesis 2: The patterns of inter-correlation among items are similar for persons with disabilities compared to persons without disabilities.

Hypothesis 3: The concurrent validity of the BRFSS/HRQOL summary score is similar for persons with and without disabilities.

Background to Hypotheses: Krahn, Drum, Horner-Johnson, and Goldsmith (2004) used Andersen’s Behavioral Model to examine predictors of health status (measured as a single question) using 1998 and 2001 national BRFSS data. In univariate analyses, disability was the largest predictor, accounting for 14% of the variance in health status. However, when blocks of other predictors were entered first into a multivariate regression model with disability status entered last, disability only accounted for 1.73% of the variance in health status. Much of the variance originally attributed to disability was accounted for by predisposing variables (gender, age, race/ethnicity), enabling characteristics (employment, education, income), need (pain, blood pressure, cholesterol levels), or personal practices (smoking, body mass index, exercise). Disability and poor health may be independently caused by similar factors, or pre-existing disability may result in social disadvantages that lead to poor health. However, disability in and of itself is not necessarily a sufficient cause of poor health, as has been presumed by measures that ascribe a lower health score to people with functional limitations. In fact, more than half of people with disabilities report excellent, very good, or good health (Drum et al., 2003). These findings suggest that a deeper understanding is needed of variables besides disability that are associated with health and wellness. High intercorrelations among the standard four HRQOL questions suggest that they might be summed into a single score. Performance of the pain question for people with disabilities and its inclusion in the definition of health and wellness for people with disabilities (Putnam et al., 2003) suggests it should also be considered for inclusion. Knowledge about the performance of the questions among people with and without disabilities, their prediction by other variables may inform development of improved health status measurement questions to assess health and well-being of individuals with disabilities regardless of functional status.

Study Design: Secondary analysis of an aggregated, population-based data set to examine intercorrelations among items.

Sample: The proposed research study would examine selected questions from the 2001, 2003, and potentially 2004 BRFSS aggregated data sets. The 2001 BRFSS data set aggregated for all states and territories includes 212,510 respondents of whom 41,380 (19.5% -- unweighted percentage) are people with self-reported disabilities. The 2003 aggregated data set contains records for 264,684 respondents, including 59,728
(22.6% -- unweighted percentage) people with disabilities. If available in time, the 2004 data set will also be included in the analyses. Up to three years of data will be employed to establish the consistency of relationships among core variables. Additionally, data from optional modules and rotating core questions that vary from year to year can be analyzed by drawing on multiple years of data.

Data Collection and Measurement Techniques: The BRFSS is a continuously conducted random dial telephone survey conducted under the auspices of the CDC for all states and territories. It contains a series of core modules with questions relating to a range of topics that affect health of the population. Optional modules vary from year to year. In 1996, an optional disability module was introduced. Two disability identifiers were added to the core in 2001 and were approved for annual inclusion beginning in 2003. Limitations of the BRFSS include bias introduced by utilizing a telephone interview (Hough, 1999), and sampling designs that may vary from state to state (Perrin & Koshel, 1998). However, the BRFSS is generally considered superior to the NHIS on area, timeliness, completeness, accuracy, and reliability (Stroup, Zack, & Wharton, 1994).

Data Analysis Methods: Responses to the four core HRQOL items will be inter-correlated to determine the relationships of the questions to each other for people with and without disabilities. Internal consistency alphas will be calculated separately for people with and without disabilities to determine whether the four items can be used as items on a scale that will yield a single summary score. The individual HRQOL questions, the Healthy Days Index (CDC, 2000), and the summary score will be compared with each other across the data for each year. Regression analyses will be conducted to determine the relationship of other variables measured by the BRFSS (e.g. demographics, health behaviors, receipt of preventive screenings, pain) to HRQOL scores. Separate regression analyses will be conducted for people with and without disabilities to determine whether the pattern of relationship is similar. In other words, the regression analyses will identify variables other than disability status that are related to health status and quality of life, and that should be included in improved measurement of health status that is not dependent on functional ability. Analyses will be conducted in SUDAAN to account for the complex survey sample design of the BRFSS.

Anticipated Findings: The internal consistency of BRFSS HRQOL questions will be ascertained across a national population-based sample of people with and without disabilities. These findings will indicate whether these measures represent a unitary construct that can serve as the basis for a measure of health status and will be used in R8. The comparability of correlation patterns among BRFSS HRQOL items among a sample of people with disabilities relative to people without disabilities and will help to determine whether a “universal” measure of health status is feasible. Finally, the comparability of items predicting to a summary score of health status for people with disabilities relative to people without disabilities will be known. This will inform consideration of additional areas to include in a new measure of health status.

Click here to access information on the previous BRFSS study.



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