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Osteoporosis (literally "porous bone") is a condition characterized by bone fragility and fracturing. The World Health Organization (WHO) defines osteoporosis as a 25 percent reduction of bone mineral density (BMD) compared to that of a healthy young adult female.

Eight million Americans have osteoporosis, and over 20 million have osteopenia (thin bones, or a loss of 10 to 25% of bone mineral density). Osteoporosis is most prevalent in Caucasians, less prevalent in Hispanics, and least prevalent in African Americans. Key predisposing factors are early menopause and a family history of osteoporosis. Other medical, psychological, and social factors may also contribute to the condition.

Osteoporosis commonly leads to fractures. Medical, social, and environmental factors that predispose people to osteoporosis-related fractures include impairment of hearing, vision, balance and cognition; debilitating illnesses; medications; postoperative conditions; and unsafe environments. In the United States, one of three females over age sixty-five will have at least one vertebral fracture. The ratio of female to male fractures of a hip is 2.5 to one. Two hundred and fifty thousand hip or wrist fractures and 500,000 vertebral fractures occur annually in the United States. Up to 15 percent of hip fractures will result in death within one year, and one of three survivors become long-term nursing home residents. The annual cost of osteoporosis in the United States is estimated to be as high as $18 million and is projected to reach $240 million by the year 2040.

There are several methods to measure bone mineral density for osteoporosis detection. The most precise is dual energy X-ray absorptiometry (DXA) of the hip. Blood and urine tests for bone resorption and formation are also used to help measure the response to therapy.

The four components of treatment are nutrition, medication, exercise, and safety. Nutritional factors are particularly important during childhood and adolescence when the bones are growing. Key components are calcium and vitamin D, supplemented by magnesium; and vitamins C and K for individuals with chronic diarrhea or on a low-vegetable diet.

Hormonal therapies—estrogens for postmenopausal females and testosterone for hypogonadal males—are widely utilized. Estrogens may be contraindicated by breast or uterine cancer or by susceptibility to vascular clotting, and prostatic disorders may preclude the use of testosterone. Bisphosphonates are potent antiresorptive drugs that can yield reductions in hip and vertebral fracturing. Use of calcitonin, another antiresorptive drug, has also shown reductions in vertebral fracturing.

Exercise and safety are essential components of fracture prevention. Vigorous weight-bearing activities are beneficial but not feasible for the elderly or infirm. Walking has not proved efficacious. Resistive exercises increase the muscle strength and bone mineral density essential to fracture prevention. Balance–enhancing activities such as dancing, careful attention to minimizing hazards in the home and work environments, and selective use of padded hip protectors for the aged and infirm all help reduce the risk of osteoporosis-related fractures.

Osteoporosis is a major and growing public health concern. Appropriate screening to identify those who are susceptible, accurate diagnosis of osteoporosis and related disorders, and prompt institution and monitoring of appropriate therapies are all essential to minimize the risks of fracture and the attendant mortality and morbidity.

ROBERT L. SWEZEY

(SEE ALSO: Hip Fractures)