Risk is not Disease
Bone density tests quickly became a rite of passage for many postmenopausal women in their 50s. When doctors started scanning these women, however, a problem emerged, says Cummings, who has co-authored some of the largest studies of osteoporosis in the past three decades. Instead of regarding “low bone density” as one sign of risk, doctors equated it with full-blown osteoporosis. Even worse, under the banner of early detection and prevention, bone density that was slightly lower than average got its own medical label—osteopenia—and some doctors started treating that condition with drugs, too.
The conflation of disease with disease risk might not be so bad, Cummings says, if bone density tracked tightly with the incidence of serious fractures at every age, under every condition. But it does not. Among 16,000 postmenopausal women in Manitoba who received baseline bone scans at age 50 or older, for example, most of those who eventually suffered fractures had normal bone density, according to a 2007 study in the Canadian Medical Association Journal. As the studies piled up, Cummings notes, “it quickly became evident that in a group of people with the same bone mineral density, some got fractures and others didn't. Clearly, some other feature of bone plays an important role here.”
That should not come as a surprise, says Markus Seibel, who studies bone metabolism at the University of Sydney. Much of modern medicine is about treating risk instead of symptoms, he notes. Doctors attempt to lower bad cholesterol in hopes of preventing a heart attack, for example. But relying strictly on numbers to predict health outcomes is tricky. “The more we move away from actual disease, the harder it is to predict what will happen in a particular patient,” Seibel says.
So far, Seibel observes, scientists have not identified the underlying physiological features that make a bone resistant or prone to cracks. Large epidemiological studies, however, have revealed more characteristics of people that, when taken together with measurements of bone density, can help improve predictions about who will suffer a major fracture. In 2008 the World Health Organization integrated 12 of the most influential of these risk factors into an algorithm that is the basis for an easy-to-use online risk calculator known as FRAX.
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4 Comments
Add Comment... "in a group of people with the same bone mineral density, some got fractures and others didn't"
Reply | Report Abuse | Link to thisAny ideas as to the actual causal mechanism for fracturing? Could there be some sort of micro-crack development due to abnormal osteoclast/osteoblast functions, thus allowing the creation of stress concentrations? Stress concentrations are geometrical anomalies, such as sharp corners, cracks, etc. which can cause a multiplication, or increase, of the otherwise normal stress levels within a structural member.
Evidence is conflicting regarding the Calcium supplements as a preventive measure for Osteoporosis, some point to increased cardiovascular events with Ca, recent work indicates that this would be negligible, benefits clearly overcoming any risk, but for sure it has been shown that as more hours you're standing, and also exercising, the higher the increases in your hip's bone density and the bigger the decreases of your chances of suffering a hip fracture is, hip fractures that are probably more dangerous than the vertebral fractures that usually induce only pain. Vitamin D supplements have also beneficial effects in other health issues, and as a matter of curiosity, there's even work pointing that the only intervention, at least in the elderly, that will improve overall health would be weekly Vitamin D supplements, every day dosing being less efficacious, and dosing with a longer time span from one to the other, specially once a year dosing, would be even detrimental.
Reply | Report Abuse | Link to thisIs wrist DXA the best approach for checking Bone Mineral Density or not?
Reply | Report Abuse | Link to thisI am a 60-year old male. I have osteoporosis, but I have never had a fracture.
Reply | Report Abuse | Link to thisI could tell that something was wrong, so I asked two different primary care physicians if I could have a DXA scan. They both said, "No. You have no risk factors". Finally a third physician agreed with me and ordered the test. The results showed osteoporosis of the lumbar spine and osteopenia of the hip and femoral neck. I was 58 at that time.
In my opinion, everyone (both male and female) should have a baseline DXA scan at age 50 (the same as is recommended for a colonoscopy). The first sign of osteoporosis should never be a fragility fracture.