Limitations on the Use of a Single Screening Question to Measure Sedentary Behavior

Tracking health hehaviors is an impoitant component of chronic disease surveillance programs. Among applicable healtli behav-iors, physical activity has been assodated with lower mortality and morbidity, whereas phys-ical inactivity or sedentary hehavior has been associated with increased mortality and mor-bidity. Thus, the prevalence of participation in physical activity in a community population provides important information for public health action. Questionnaires are the most commonly used tool for assessing the prevalence of health hehaviors in population-based surveil-lance systems. Because of the cost of large surveys, questionnaires usually are designed to classify a behavior with tlie fewest number of questions possible. Although a shorter sur-vey is desirable for reducing costs, it could limit the ability to draw inferences about spe-dfic outcomes of interest. For example, to ex-amine fitness-related outcomes, a single ques-tion has reasonable validity in some, but not all, studies.'" ^ However, to determine health-related outcomes associated with moderate-intensity physical activity, the intei:isity, fre-quency, and dm ation of the activity must be determined. Because of the difficulty in chai-actedzing the various components of physical activity, surveillance effoiis focused on physi-cal inactivity may be more effident than try-ing to identify physically active individuals. This study assessed tlie limitations assod-ated with use of the physical activity screen-ing question from tlie state based Behavioral Risk Factor Surveillance System (BRFSS) to identify sedentary behavior and the appKca-bilify of this screening question to designing and tracking communify interventions