Which statement best describes the relationship between bone mineral density and fracture risk?

• A. Higher BMD increases fracture risk.
• B. Lower BMD is associated with higher fracture risk; FRAX uses BMD to refine risk.
• C. BMD and fracture risk are unrelated.
• D. FRAX does not consider BMD.

Answer: (B)

The relationship being tested is that bone strength is largely determined by bone mineral density: the lower the BMD, the weaker the bone, and the higher the risk of fracture under normal loads or minor falls. This is why osteoporosis, defined by low BMD, is tied to greater fracture risk.

FRAX is a fracture risk assessment tool that combines a person’s clinical risk factors (age, sex, prior fracture, smoking, glucocorticoid use, rheumatoid arthritis, secondary osteoporosis, alcohol, etc.) with bone mineral density data to estimate the 10-year probability of a hip or major osteoporotic fracture. Including BMD refines the risk estimate because it provides a direct measure of bone strength; when BMD is available, FRAX can yield a more precise probability, helping to decide who might benefit from treatment. Without BMD, FRAX can still be used, but the assessment is less precise.

So, lower BMD is associated with higher fracture risk, and FRAX uses BMD to refine risk.