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Post-Polio Health

(ISSN 1066-5331)

Vol. 9, No. 3, Summer 1993
Osteoporosis, continued

Nutritional factors, primarily inadequate calcium and vitamin D intake, are implicated in the development of osteoporosis. Our need for calcium increases as we grow older because of less efficient intestinal calcium absorption, and other causes. The recommended calcium intake for young adults is between 750-1000 mg per day. Healthy premenopausal women over age 30 need about 1000 mg calcium per day (that amount contained in one quart of milk) and pregnant and lactating women need 1500 and 2000 mg per day, respectively. Individuals over age 50 need 1500 mg calcium per day. Unfortunately, the average American woman consumes less than 500 mg calcium per day and thus is in a chronic state of calcium deficiency.

Vitamin D is needed for intestinal absorption of calcium. The active form of vitamin D is produced in our skin by a reaction stimulated by ultraviolet radiation (in sunlight). Certain behavioral factors important in the development of osteoporosis have also been identified. Daily weight-bearing activity is essential for skeletal health. Studies have shown a direct relationship between weight-bearing activity and bone mass. In addition, behaviors such as cigarette smoking and excessive alcohol intake can induce bone loss.

Prevention of osteoporosis is currently the only reasonable management approach for this condition. An adequate calcium intake should be maintained in postmenopausal women. Calcium supplementation at doses of 1000 mg per day or more may decrease postmenopausal bone loss by as much as 50% at some sites. The result in premenopausal women from such supplementation are unclear. However, calcium supplementation has not been shown to replace the effects of estrogen-replacement therapy in postmenopausal women. Vitamin D supplementation may also be needed. Weight-bearing exercise such as walking or aerobics (if possible) should be encouraged. There appears to be a relationship between degree of weight-bearing exercise and bone mass. In addition, a regular weight-bearing exercise program has been shown to increase bone mass in postmenopausal women. Cigarette smoking and excessive alcohol intake should be avoided because these behaviors can be damaging to bone. If possible, drugs that can cause bone loss should be avoided.

In those patients who have a low or relatively low bone mass, medications may be necessary to reduce postmenopausal and age-related bone loss. Currently the most effective treatment for this is estrogen-replacement therapy started at menopause. Estrogen therapy is most effective when started early after menopause. Estrogen therapy can prevent early postmenopausal bone loss, can increase bone mass in the spine by 5% in women with osteoporosis, and can reduce fractures by 50%.

Estrogen use, however, has certain associated risks such as an increased incidence of endomentrial cancer and possibly an increased incidence of breast cancer. Estrogen therapy is also contraindicated in certain patients. In women who are unable to take estrogen or in men, calcitonin can be used. Currently, calcitonin is administered intravenously. A form of calcitonin which can be administered with a nasal spray is available in Europe and is undergoing evaluation for use in North America. Calcitonin has been shown to transiently increase trabecular bone mass and to retard bone loss from cortical bone in postmenopausal women. Fluoride increases bone mass, however, the bone formed was found to be abnormal and more susceptible to fracture. It is possible that a lower dosage of fluoride may still be helpful. Other possible treatments that are currently undergoing evaluation are biphosphonates, parathyroid hormone and growth factors.

The prevention of osteoporosis-related fractures should also include strategies to reduce the risk for falls. Prevention of falls can involve various measures such as discontinuation of sedating medications, use of a leg brace, use of a cane or crutch to improve balance, use of rubber-heeled shoes, absence of "throw rugs," and use of a nightlight.

In conclusion, even though much work remains to be accomplished on the prevention and management of osteoporosis, some recommendations and specific treatments are available. New medications may become available in the next decade that are more easily administered and are more effective in treating established osteoporosis.

References

1. Chestnut, CH. Osteoporosis. In DeLisa JA, ed. Rehabilitation Medicine: Principles and practice. Philadelphia, PA: J.B. Lippincott 1988; 865-875.

2. Kaplin, FS. Osteoporosis: pathophysiology and prevention. In Clinical Symposia: 1987 Annual (vol. 39 #1). Summit, NJ: Ciba-Geigy Corp. 1987; 1-32.

3. Riggs, BL, Melton, LJ. Involutional osteoporosis. N. Engl J. Med. 1987; 314: 1676-1686.

4. Riggs, BL, Melton, LJ. The prevention and treatment of osteoporosis. N. Engl. J. Med., 1992; 327: 620-627.

5. Sinaki, M, Offord, KP. Physical activity in postmenopausal women: Effect on back muscle strength and bone mineral density of the spine. Arch. Phys. Med. Rehabil. 1988; 68: 277-280.

Resources

National Osteoporosis Foundation, 1150 17th St., NW, Suite 500, Washington, DC 20036 USA (202-223-2226) offers educational materials.

"Osteoporosis: The Bone Thinner," "Menopause, Managing Menopause," and "Should You Take Estrogen?" are available from National Insitute on Aging, PO Box 8057, Gaitehrsburg, MD 20898-8057 USA (800-222-2225). They will also send a complete listing of their publications upon request.

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