Hyperkyphosis refers to an excessive curvature of the thoracic spine, commonly known as the """"""""Dowagers hump."""""""" It is frequently observed in the older population, and yet little is known about its causes or consequences. It is generally assumed, but not proven, that hyperkyphosis primarily results from vertebral fractures, although previous small studies suggest that osteoporosis only accounts for less than half of hyperkyphosis. Potential other causes of hyperkyphosis include a genetic predisposition, degenerative disc disease, and muscular weakness. Hyperkyphosis is associated with adverse outcomes including restricted pulmonary function, poor physical function, and an increased risk of mortality that is not accounted for by vertebral fractures. These previous studies suggest that hyperkyphosis is an important clinical indicator of poor health. However, there are no set clinical criteria that define what degree of kyphotic angle constitutes hyperkyphosis. Therefore, defining hyperkyphosis and determining its causes and consequences has important implications for the health of older patients. To define hyperkyphosis, understand its pathogenesis and learn its health outcomes, we propose to conduct a series of analyses using an existing comprehensive data set, the Study of Osteoporotic Fractures (SOF). SOF is the first and largest prospective U.S. study devoted primarily to the study of osteoporotic fractures in older women. Since 1986, participants have attended serial exams of risk factors for fractures and other chronic diseases. In this study, we propose to measure the kyphotic angle from existing baseline radiographs and from repeated radiographs taken an average of 3.5 and 15 years after baseline. We created a digitization program that calculates the most widely used radiological measure of kyphosis, the Cobb angle. Thus, a reliable measure can be made in a large number of subjects with minimal effort. Using existing data from SOF, we will: 1) quantify the kyphotic angle in 1000 older women and determine how much of hyperkyphosis is due to underlying osteoporosis and how much is related to other potential risk factors including a genetic predisposition, muscle weakness, intervertebral disc height loss, and health behaviors; and 2) define what degree of kyphoUc angle constitutes hyperkyphosis by its association with important outcomes including falls, fractures, and functional limitations. This is the first comprehensive study of the causes and consequences of hyperkyphosis. This cost-effective and innovative use of an existing data set is likely to produce the first systematic analyses of this common condition.
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