Projected population of persons age 65 and older, 1990–2050 Foundation (NOF) in 2004, the bone-thinning and -weakening disease has afflicted more than ten million people, and more than thirty-four million more are estimated to have low bone mass, placing them at increased risk for osteoporosis. By 2020, approximately fourteen million Americans will have osteoporosis and more than forty-seven million will have low bone mass. The condition likely is present, to some degree, in more than half of all Americans older than age fifty years. About 80 percent of those affected are women. People of any race can develop osteoporosis; however, whites and Asians generally have 10 to 20 percent lower bone mineral density than do African-Americans or Hispanics and thus are at higher risk of developing osteoporosis.
Bone density builds up during childhood growth and reaches its peak in early adulthood. From that point on, bone loss gradually increases, outstripping the body's natural ability to replace bone. The denser a person's bones are during the growth years, the less likely he or she is to develop osteoporosis. Proper diet, especially eating foods rich in calcium and vitamin D long before the visible symptoms of osteoporosis appear, is vitally important.
About one-third of a person's risk of developing osteoporosis is hereditary. In 1994 an Australian research team identified a gene linked to bone density. Two forms of the gene, B and b, exist. People with two b genes, one from each parent, have the highest bone density and are least likely to develop osteoporosis, whereas those with one of each, the Bb genotype, have intermediate bone density. People with two B genes have the lowest bone density and the highest risk of osteoporosis. Women with the BB genotype may be four times as likely to experience hip fractures as those with the bb genotype.
The gene discovery was hailed as the most important finding in the osteoporosis field in a decade. Although much research remains to be done, researchers hope the identification of the gene eventually will lead to a simple test to identify children at risk for osteoporosis in later life. The test would allow doctors to prescribe an increased intake of calcium and protein during the growth years for these children, thus preventing or delaying the onset of osteoporosis.
Osteoporosis worsens with age, leaving its victims at risk of broken hips or other bones, curvature of the spine, and other disabilities. An estimated 8 million women (non-Hispanic white women are disproportionately affected) have a severe form of the disease, which causes many of them to experience spontaneous (without external causes) fractures, generally in the vertebrae of the spine.
Treatment of Osteoporosis
The primary goal of therapy is to prevent fractures. Nonpharmacologic (without medicine) preventive measures to help prevent osteoporosis include diet modification (an increase in the intake of calcium and vitamin D), exercise programs, and fall-prevention strategies. Current pharmacologic (medication) therapies improve bone mass and reduce fracture risk.
Most of the agents currently available in the United States act by inhibiting bone resorption. Estrogens, selective estrogen receptor modulators (SERMs), bisphosphonates, calcitonin, calcium, and vitamin D all have antiresorptive properties. The SERM raloxifene and the bisphosphonates alendronate and risedronate all are approved for the prevention and treatment of post-menopausal osteoporosis. A number of agents that have a clear ability to increase bone formation (and are therefore anabolic agents) are being studied for use in the treatment of osteoporosis and prevention of fractures, according to The State of the Art in the Management of Osteoporosis, published jointly in January 2004 by the Office on Women's Health of the U.S. Department of Health and Human Services and Columbia University's College of Physicians and Surgeons.
At the end of the twentieth century, the traditional treatment for postmenopausal women with osteoporosis, or those at risk for the disease, was hormone replacement therapy (HRT), often combined with daily doses of calcium and regular weightbearing exercise, such as walking and exercising with weights. This treatment slows the advance of the disease and helps to prevent fractures and disability. Due to serious side effects of HRT that became known in July 2002—including documented increased risks of cardiovascular disease and certain types of cancer—many women have discontinued HRT treatment. For women with lower side effect risk factors, however, HRT is still available.
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