The Myth of Osteoporosis.

Are We Being Over-Diagnosed?

Concerns about an over diagnosis of osteoporosis are often referred to as the myth of osteoporosis. DXA tests are imperfect-but they will not cause undue alarm if treated as a single tool in a comprehensive osteoporosis prevention program.



With bone fractures and hip replacements costing millions of dollars each year, most developed nations would argue that the myth of osteoporosis is a reality once the population begins to age. So why is there concern about the over diagnosis of osteoporosis?

The World Health Organization (WHO) describes osteoporosis as “a progressive systemic skeletal disease, characterized by low bone mass and micro-architectural deterioration of bone tissues, with a consequent increase in bone fragility and susceptibility to fracture.” With this dual focus in mind, it would be ideal if we measured bone health both in terms of the quality of bone as well as the quantity of bone (bone mass). But the current emphasis is on bone density which some argue is misleading and creates the myth of osteoporosis.


THE BONE DENSITY STANDARD IS IMPERFECT

Dual X-ray Absorptiometry (DXA), the internationally recognized gold standard for determining fracture risk, measures bone mineral density (BMD) but not bone quality. The WHO has established an international standard which gives a BMD reading of 2.5 standard deviations below normal a diagnosis of osteoporosis while readings of 1-2.5 standard deviations below normal are classified as osteopenia-the early stage of osteoporosis. For each standard deviation decrease in bone mineral density, doctors are warned that fracture risk will likely double.

There are two problems with these guidelines. The first is that the “normal level” (known as a T-score) is based on the average peak bone density of a young white woman. The natural variations amongst healthy adults and normal age-related bone loss are not accounted for by this definition, although studies have shown that peak bone mass varies substantially between men and women and amongst ethnic groups. Measuring a man’s BMD is a particular challenge under this definition, as men generally have taller and larger skeletons than women. The DXA adjusts for the area scanned but does not completely correct for the fact that wider bones are also thicker. Bigger bones may appear to have greater BMD even if the actual tissue density is not different. In elderly spines, compression fractures, arthritis and other factors can also create artificially dense bone in the vertebrae making the readings of little use. The failure of the DXA to account for these differences is referred to as the myth of osteoporosis by those concerned about over diagnosis of the condition.


DXA MACHINES USE DIFFERENT STANDARDS

A second challenge with the use of DXA as a diagnostic tool is that there is no international normal reference standard for DXA machines. Manufacturers set their own (often high standards) resulting in widely varying diagnoses. Results will vary between machines and also amongst regions and countries. The error for DXA measurements can be up to 8% (almost one standard deviation) which could significantly change a diagnosis.

A number of research studies found that the inconsistent and high standards set by manufacturers were causing unusually high number of diagnoses of osteoporosis and subsequent medication use when there was only a very small risk of a fracture. Some even accuse the pharmaceutical companies of creating the myth of osteoporosis in order to increase medication sales. Concerns about consistent testings can often be addressed by simply requesting that the DXA test be repeated on the same machine.

People should also assess their DXA results in light of their risk of osteoporosis and understand that it is natural to lose bone density as we age. If a test shows a modest decline in density but the person has few risk factors…the decline is likely due to the natural aging process.

Peak bone mass (PBM) usually occurs around age twenty with genetic factors accounting for 60-80% of the variability in PBM. Diet, physical activity and hormonal status are also important factors. Our PBM tends to remain stable until the late 30’s and 40’s and then begins to decline but at different rates for each person. Women on average lose between one-third and one-half of their peak bone mass over their lifetime, while men generally begin with greater bone mass and lose less over their lifetime.

As a preventive strategy, it is always good to review our diet and exercise regime as we go through different stages of life. Medication is only a consideration for the small portion of people who are at risk of fracture(20% of women and 5% of men) while improving our diets and exercise is a winning strategy for everyone. Supplements with recommended levels of calcium, vitamin D, magnesium and vitamin K are also invaluable in a bone building program.

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