Osteoporosis ("porous bone") is a major public health problem and the leading cause of bone fractures in post menopausal women and older adults. Although all bones are affected, the most common fractures caused by osteoporosis occur in the spine, wrist, and hip. An estimated 10 million people have osteoporosis (80% are women) and 18 million more have low bone mass placing them at risk for the disease. Women have more fractures than men, and whites have more fractures than blacks.

An estimated 1.3 million fractures of the wrist, spine, and hips a year occur annually in Americans age 45 and older as a result of this disease. About half of those who break their hips end up in nursing homes, and about 20 percent will die in the year following the fracture. Less than one in three persons with a hip fracture return to their previous level of function. One in three women

Osteoporosis in the United States costs an estimated 3.8 billion annually.The table below show the lifetime risk for the most common osteoporotic fractures.

Lifetime Risk for an Osteoporotic Fracture in the United States at Age 50 by Sex

Fracture	Women	Men
Arm	16%	2.5%
Spine	15.6%	5.0%
Hip	17.5%	6.0%

After menopause, women can lose up to 2 to 3% or more bone mass per year. In particular, bone loss is accelerated for up to 10 years after onset of menopause as the body adjusts to a reduction in estrogen. After about a decade this bone loss slows down and approaches the rate of decline found in older men. Women can lose up to 50 percent of their peak bone mass by age 70 or 80.

Osteoporosis is often first detected when a fracture occurs-- either spontaneously (e.g., the spine) or as a result of minor trauma (e.g., hip). By this time, bone loss is usually significant. A common symptom is back pain following vertebral fractures that can accumulate and result in a dowager's hump. A significant loss of height (more than 1 inch) may be an early sign of osteoporosis.

Risk Factors for Osteoporosis

• Post-menopausal females
• Age
• Family history
• Thin stature
• Underweight
• Medications that accelerate bone loss (e.g. corticosteroids)
• Calcium-poor diet
• Sedentary lifestyle

Prevention of Osteoporosis

Prevention is important since it is difficult to treat and can lead to significant disability..

1. Estrogen Replacement Therapy (ERT). ERT is the most effective way to prevent osteoporosis in postmenopausal women. There is a substantial reduction in rate of wrist, hip and spine fractures in women who begin ERT within a few years of menopause. For example, women who take estrogen lower their risk for hip fracture by 50 percent. For the most benefit, ERT should begin at menopause and continue for life. Effective doses of conjugated estrogens (0.625 to 1.25 mg) can be quite low. Selective estrogen receptor modulators (SERMs) such as raloxifene (e.g., evista) have recently been approved for the prevention of osteoporosis. SERMs mimic the effects of estrogen on bone without increasing risk of breast or uterine cancer. However, the gains in bone mineral density are more modest than those of conjugated estrogens.

2. Diet. Getting adequate amounts of calcium and vitamin D through diet or supplements at all stages of life should be a priority. A lifelong calcium deficiency can contribute to osteoporosis. Mild vitamin D deficiency can contribute to osteoporosis by increasing bone resorption. Premenopausal women and postmenopausal women on estrogen need 1000 mg and postmenopausal women not on estrogen need 1500 mg a day. Men younger than age 65 need 1000 milligrams (mg) and those over 65 need 1500 mg of calcium a day.

   A high alcohol intake (more than 3 drinks/day) can compromise bone density by affecting the liver where vitamin D is activated, by interfering with calcium absorption, or by being toxic to bone cells. Excessive caffeine intake is associated with reduced calcium absorption or excess excretion.

3. Exercise. Exercise can reduce bone loss, even in post-menopausal women. The type of activity is important--weight-bearing exercise (e.g., running, tennis) is more effective than low-impact activities such as swimming.

Diagnosing Osteoporosis

Until recently the best screening tool for osteoporosis was the dual energy X-ray absorptiometry scan, or DEXA. It accurately measures bone density at the spine, hip and wrist using only a low amount of radiation. Unfortunately costs up to $300 and insurance does not always cover it. Fortunately, two new portable devices have been approved for measuring bone density that can be used in a doctors office. Both devices use ultrasound (high frequency sound waves) rather than radiation to measure bone density. The Sahara is a heel bone scanner and the SoundScan is a calf bone scanner. Based on the measurements, one can estimate fracture risk in other parts of the body. The tests do not require a highly trained technician and cost only about $40. However, they may not be as sensitive as DEXA in detecting mild osteoporosis.

Treating Osteoporosis

Treatment of osteoporosis emphasizes drug therapy to maintain or increase bone density, exercise to increase muscle strength, adequate calcium intake and reducing the risk of fractures through fall prevention strategies. Drug therapies include:

• Bisphosphonates. Bisphosphenates (e.g., Fosamax, Didronel, Aredia) are not hormones but they can inhibit bone resorption and increase bone density by increasing bone formation.

  These medications must be taken properly to receive their benefits. For example, Fosamax must be taken on an empty stomach in the morning. After taking the medicine, for at least 30 minutes the patient cannot eat anything and must remain upright to prevent esophageal irritation. Other bisphosphonates have different requirements.

• Calcitonin. Calcitonin (e.g. calcimar, miacalcin, osteocalcin) slows bone resorption. It is available now in an intranasal formulation that is more convenient than the injections that were formerly required. Calcitonin can increase bone density by 2 to 3% over the course of 2 years of drug therapy.

• Calcium Supplements: Calcium supplements can slow bone loss in postmenopausal women although they cannot substitute for HRT.