How does the bone density test define osteoporosis?
A diagnosis of osteoporosis is defined in terms of standard deviations from the average peak bone mass. The World Health Organization defines osteoporosis as a bone mineral density 2.5 standard deviations below that of a normal healthy 30 year old. Those who are between 1 and 2.5 standard deviations below the norm are defined as having osteopenia or low bone mass. Individuals within one standard deviation of the 30-year-old norm are considered to be at low risk for osteoporotic fracture.
