When you say "osteoporosis," most people know what you are talking about. But when you mention "osteopenia," it's common for someone to say, "What's that?" That's because osteopenia is a relatively new term used by doctors to describe bone density.
The term osteopenia was created shortly after the development of the dual-energy X-ray absorptiometry (DEXA) scan. A DEXA scan is used to measure bone density at the hip and spine, where fractures are most likely to occur. It is now widely used to monitor bone health.
Before the machine was put into widespread use, an international group of medical experts met to determine a consistent method for using DEXA scan readings. They decided to use a T score, which uses a statistical term called standard deviation. Standard deviation measures how far something is away from the norm; in this case, the “norm” selected was the bone density of a healthy, average woman in her mid-20s. They also decided that a –2.5 standard deviation below the norm would be used as the definition for osteoporosis.
The next question they faced was: What should we do about women who scored less than –2.5 and who did not yet have osteoporosis? They decided it was important for these women to be aware that they had already had some bone loss. So they created a new term to classify these women, and that term was osteopenia. And they decided that the cutoff for osteopenia would be –1.
Today, any woman who scores between –1 and –2.5 on her DEXA scan is told that she has osteopenia. But there was no real medical basis for developing this term or choosing that number, says bone health expert Steve Cummings, MD, a former professor of medicine and epidemiology at the University of California, San Francisco School of Medicine. In addition, Cummings says that when the term was developed, no one paid attention to the fact that it would result in half of all postmenopausal women being told they had this "disease"—with the implication that they should begin taking drugs to treat it.
But as Cummings points out, "Osteopenia is not a disease, does not indicate a high risk of fracture in the next five to 10 years, and is really almost a variant of normal."
If a woman learns she has osteopenia at age 55, he explains, it means she is just around average.
"What I tell women in their 50s," he says, "is that having osteopenia means their bones are different than those of a 25-year-old, and I note that there are probably many things about them that differ from when they were 25. And I let them know that it is nothing to be alarmed about."