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Variables
Our study used the following 9 HRQOL questions from the 2004 Rhode Island BRFSS: 1) self-rated general health status; and self-reported number of healthy and unhealthy days in the previous 30 days for 2) physical health, 3) mental health, 4) physical or mental health-related activity limitation, 5) pain-related activity limitation, 6) sad, blue, or depressed, 7) worried, tense, or anxious, 8) lack of rest or sleep, and 9) lack of energy (1,2,15). We created 9 dichotomous indicator variables. The responses to the self-rated general health status question were dichotomized into "poor" (poor or fair) health or "good" (good, very good, or excellent) health. The indicators measured in days were dichotomized at a cutoff value of 14 or more days of poor health in the previous month compared to less than 14 days (3). We selected the 14-day minimum period because most of the publications we reviewed that use the BRFSS HRQOL indicators (outcomes) use the cutoff of 14 or more days compared to 13 or fewer days (3-5,7-11,16,17). Adopting this precedent ensured comparability. In addition, clinicians and clinical researchers often use this period as a marker for clinical depression and anxiety disorders, and long symptomatic durations are associated with high levels of activity limitation (2,18). Detailed definitions of the 9 indicators are available in our previous article (1) or are accessible through the Centers for Disease Control and Prevention's HRQOL Web site (2).
We chose 12 predictors for the analysis: 5 standard demographic measures (age, sex, race/Hispanic ethnicity, annual income, and employment status); 4 health conditions (asthma, diabetes, obesity, and physical disability); and 3 health risk behaviors (smoking, chronic alcohol use, and no leisure-time physical activity). These predictors paralleled the results of other studies that have examined relationships between a specific HRQOL indicator and various predictors (17,19), or that have examined multiple HRQOL indicators in relation to demographics (4,20), health risks (5,10,21), or specific health conditions (6-9,12,22). We dichotomized some predictors for the analysis (ie, sex, current smoking, alcohol use, physical activity, asthma, diabetes, obesity, and disability), whereas other predictors had multiple categories (ie, age, race/Hispanic ethnicity, income, and employment status). The definitions of the 12 predictors are available in our previous article (1). Reference groups chosen for the IRT model were those having the lowest risk for poor or fair general health and usually the lowest risk for the other HRQOL variables as well.
