Osteoporosis Definition

Osteoporosis occurs when the amount of bone is decreased and the structural integrity of trabecular bone is impaired. As cortical bone becomes more porous, the bone becomes weaker, making it more likely for a fracture to occur.

The World Health Organization (WHO) has defined osteoporosis based on the T-score—the number of standard deviations (SD) from the mean (average) value of a 25-year-old female.

• Normal bone: T-score > -1
• Osteopenia: T-score between -1 and -2.5
• Osteoporosis: T-score < -2.5

A diagnosis of osteoporosis also includes the presence of a non-traumatic fracture.

The Prevalence of Postmenopausal Osteoporosis

• In the United States, osteoporosis is a major public health threat for approximately 30 million people. Of these, approximately 68% are women¹
• Approximately 8 million people are estimated already to have the disease¹
• 22 million have low bone mass or osteopenia, which puts them at risk of osteoporosis¹
• Osteoporosis is responsible for more than 1.5 million fractures annually²
  • 300,000 hip fractures
  • 700,000 vertebral fractures
  • 250,000 wrist fractures
  • 300,000 fractures at other sites
• $18 billion is estimated to be spent each year in hospital and nursing home care for osteoporosis and related fractures¹
• Osteoporosis is more prevalent in Caucasian and Asian women

Osteoporosis and Menopause

The decline of ovarian estrogen production that accompanies menopause or oophorectomy, resulting in the acceleration of bone loss and bone resorption.

Bone resorption is increased more than bone formation, especially in the early years of menopause when bone loss is the greatest. In many cases, these changes will eventually lead to decreased bone mass, osteoporosis, and increased risk for fractures, particularly of the spine, hip, and wrist. In postmenopausal women, vertebral fractures are the most common type of osteoporotic fracture.

Women lose up to 10% of their cortical bone mass and up to 30% of trabecular bone mass within the first 8 years of postmenopause, as serum estradiol levels drop¹

Women discontinuing hormone therapy (HT) for postmenopausal vasomotor symptoms (VMS) begin to lose bone at the same rate as those who never used HT⁴

82% of all fractures occur in postmenopausal women with osteopenia plus 1 additional risk factor while only 18% of fractures occur in women with osteoporosis⁵

Risk factors for osteoporosis⁵

References:
1. U.S. Department of Health and Human Services. Bone Health and Osteoporosis: A Report of the Surgeon General. Rockville, MD: U.S. Department of Health and Human Services, Office of the Surgeon General, 2004. Available at www.surgeongeneral.gov/library. Accessed 10/18/2004.
2. National Osteoporosis Foundation. Web site. Accessed 7/26/2004.
3. National Osteoporosis Foundation. Web site. Accessed 7/26/2004.
4. MENOSTAR prescribing information. Montville, NJ: Bayer HealthCare Pharamceuticals, Inc; 2004.
5. Siris ES, Chen YT, Abbott TA, et al. Bone mineral density thresholds for pharmacological intervention to prevent fractures. Arch Intern Med. 2004;164:1108-1112.