How much is the risk of fracture increased for each standard deviation (SD) reduction in bone mineral density (BMD) in patients with osteoporosis?

Updated: Jan 20, 2021
  • Author: Rachel Elizabeth Whitaker Elam, MD, MSc; Chief Editor: Herbert S Diamond, MD  more...
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For each SD reduction in BMD, the relative fracture risk is increased 1.5-3 times. Of note, about half of osteoporotic fractures occur in women with a T-score greater than –2.5, and the other half occur in those with a T-score lower than –2.5, the WHO’s cutoff for DXA-based diagnosis of osteoporosis.

This diagnostic classification should not be applied to premenopausal women, men younger than 50 years, or children. Instead, Z-scores adjusted for ethnicity or race should be used, with values of –2.0 SD or lower defined as "below the expected range for age" and those above –2.0 SD being "within the expected range for age." The diagnosis of osteoporosis in these groups should not be based on densitometric criteria alone.

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