ABSTRACT:The National Osteoporosis Foundation and American College of ObstetricsGynecology have expanded osteoporosis therapy recommendations by changing the treatment threshold. We determined the impact of this recommendation using nationally representative U.S. data. The new threshold changes the number of women for whom treatment is recommended from 6.4 million to 10.8 million among women age sixty-five and older (at a net cost of at least $28 billion) and from 1.6 million to 4.0 million among women ages 50-64 (at a net cost of at least $18 billion). Whether or not offering treatment to these additional women will reduce the number of hip fractures is unknown. [Health Affairs 26, no. 6 (2007): 1702-1711 10.1377/hlthaff.26.6.1702 T r a d i t i o n a l ly, a d i s e a s e was something a patient experienced directly (and typically suffered from). Increasingly, diseases are being defined more broadly. For example, conditions that have historically been considered risk factors for diseases such as heart attack, stroke, and diabetes are now being treated as diseases in their own right. Examples include high cholesterol (hyperlipidemia), hypertension, glucose intolerance, and osteoporosis. 1 Broadening disease definitions can have major implications. Some patients may benefit from treatment that they would not otherwise have received. But broadening disease definitions also means that more people become patients. Simply labeling people as diseased leads to worry and has been shown to make people feel and act sick. 2 Also, as more patients are diagnosed, more are treated, thus exposing them to the potential harms of treatment. Finally, as the number of patients grows, spending rises.Osteoporosis is a prime example of the broadening of a disease definition. Prior to the 1990s, osteoporosis was a clinical diagnosis reserved for patients experiencing painful fractures (most commonly vertebral) not associated with major trauma. Since 1994, the definition (promulgated by the World Health Organization, or WHO) combines patients H e a l t h T r a c k i n g