Individuals with osteoporosis experience gradual loss of bone minerals, leaving bones weak and vulnerable to breaks or fractures. It is estimated that roughly half of all women over 50 years old will suffer an osteoporosis-related fracture.

While calcium supplements and other dietary and lifestyle changes may prevent osteoporosis or slow its progression, some prescription drugs also may help by increasing bone density. The current study will determine which of two leading medications is more effective for the prevention of osteoporosis fractures. The Food and Drug Administration (FDA) has approved both drugs.

Interested individuals who have not had spinal fractures, lumbar spinal fusion surgery, breast or endometrial cancer and are not being treated for osteoporosis will receive a free bone density test. Women whose tests reveal signs of osteoporosis will receive vitamin D, calcium supplements and one of two FDA-approved drugs, Evista or Fosamax, for five years. Participants also will receive follow-up evaluations every six months, including spinal X-rays, mammograms and bone density tests as needed.

All tests and drugs are free of charge, and the results will be made available to participants' primary physicians.