A sedentary lifestyle has been shown to be an independent risk factor for markers of cardiovascular disease risk (Jakes et al, 2003) and the development of cardiovascular diseases (Sidney et al, 1996). Despite the health risks, estimates of the percentage of Americans who are sedentary range from 30 to 40% (Sidney et al, 1996;Yancey et al, 2004). It has been shown that African Americans spend more time engaged in sedentary behaviors than do their Caucasian counterparts (Sidney et al, 1996;USDHHS, 2001). One report has shown that nearly 60% of African American men and women live a sedentary lifestyle (Karter et al, 1998). African Americans suffer disproportionately from various health conditions, including obesity, hypertension, and diabetes. It appears that sedentary behavior is a contributing factor to the health status of African Americans. Thus, African American adults are prime targets for studying the relationship between sedentary behavior and cardiovascular disease, and are also ideal targets for intervention designed to decrease sedentary behavior. Sedentary behavior has traditionally been assessed via self-report. These self-reported measures are subject to a number of potential problems, including recall bias, assessment only during leisure time, and lack of validation against an objective measure. Thus, there is a need for an objective measure of sedentary behavior. Accelerometers provide a way to objectively measure sedentary behavior. Currently, thresholds for light, moderate and vigorous activity have been developed for adults, yet there are no thresholds that are used to define sedentary behavior. The need for adult cut-points for sedentary behavior was expressed Matthews (2005). The primary aims for the study are threefold. One of the primary aims of the study is to develop objective thresholds of sedentary behavior in adults.
The second aim of the study is to develop and validate a self-report measure of sedentary behavior.
A third aim of the study is to develop and assess the effectiveness of an intervention designed to reduce physical activity in adults. All of these aims will be achieved in samples of African American adults. To establish cut-points for sedentary behavior, each participant will wear an accelerometer while engaging in a series of activities ranging from sedentary to moderate physical activity, including resting, watching TV, sitting a desk, reading a book, and walking on a treadmill. In order to develop a self-report measure of sedentary behavior, activities less than 1.5 METs will be extracted from the Compendium of Physical Activities (Ainsworth et al, 2000). The measure will be administered while participants wear an accelerometer for two, one-week periods in order to establish the test-retest reliability and criterion validity of the self-report measure. The relationship between objectively defined sedentary behavior and health outcomes will be assessed by applying the cut-points to the accelerometers that were used in the Jackson Heart Study (JHS). The JHS is an epidemiological study of the antecedents of cardiovascular disease in African American adults. Over four hundred of those enrolled participated in the Diet and Physical Activity Substudy, which required that they wear an accelerometer at baseline. Following this initial study, a second study will be planned that is designed to decrease sedentary behavior in African American adults. This will involve recruiting a new sample of participants. These adults will be recruited from a large Southern city and will be randomly assigned to either the intervention group or the control group. The Social Cognitive Theory guides the development of the 6-month intervention program. The control group will attend several sessions over this same time frame that focus on providing information on physical activity. The primary outcome variable, minutes of sedentary behavior, will be assessed via accelerometers.
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|Sisson, Susan B; Church, Timothy S; Martin, Corby K et al. (2009) Profiles of sedentary behavior in children and adolescents: the US National Health and Nutrition Examination Survey, 2001-2006. Int J Pediatr Obes 4:353-9|