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MONITORING AND ENHANCING
. Bones grow until a maximal skeletal mass is achieved in young adulthood. Insufficient accumulation of bone mass during the growth years predisposes to fractures later in life. At about age 35 years bone begins to be slowly lost (about 1% per year) in both men and women. After menopause women have an additional, rapid, loss of bone attributed to estrogen deficiency. This excess loss may be 10 to 15 percent in the arms and legs, and 15 to 20 percent for the spine during the first 4 to 8 years after menopause. About 15 to 20 years after menopause women begin to develop fractures when the bone mass has decreased by 50 to 75 percent. The most common sites of fracture are the hip (femoral head), spinal (vertebrae), and wrist (radius). The remaining lifetime risk of an osteoporosis-related fracture in a 50 year old US woman is 17.5% for the hip, 11% for the spine, and 13% for the wrist.
. A thorough history and physical examination, followed by basic laboratory tests should be done to rule out endocrine diseases, such as hyperthyroidism, hyperparathyroidism, and adrenal cortisol excesses, as well as gastrointestinal diseases of malabsorption and bone cancers.
. Fractures seen on x-ray are one way to diagnosis osteoporosis. Since up to half of spine fractures are asymptomatic, x-rays are necessary to detect existing fractures. However, osteoporosis cannot be diagnosed from the appearance of the bone on a plain x-ray--bone density measurements are necessary to quantify osteoporosis. The existence of fractures is a risk factor for future fractures. For example, women with a spine fracture have about 3 times the risk of a future fracture compared to women with no spine fractures. Women with 2 or more spine fractures have 6 to 9 times the risk of future fractures (Ann Intern Med 114:919, 1991). The presence of previous fractures indicates the fragility of the bones and also the tendency to injure oneself. A combination of low bone mass and just one vertebral fracture increases the relative risk of a second fracture by as much as 25-fold.
. Bone mass is a "risk indicator"--a major determinant of bone strength to estimate the risk of fractures before they happen. This mass can be measured by a variety of techniques, and expressed as "bone mineral density" (BMD). During the average lifetime, BMD of the hip decreases by 50% in women and 35% or more in men in the United States. BMD is derived from the degree of attenuation of a beam of photons from a radioactive source or x-ray tube after passing through bone and the surrounding soft tissue. BMD is expressed in relation to reference data known as standard deviation scores. These scores represent the density of the bone compared to reference values of young adults or of age-matched people with healthy bones.
. Normal is defined as a value within one standard deviation (SD) of the reference. Standard deviations below -2.5 are defined as osteoporosis, and scores in between, -1 and -2.5, define a low bone mass, known as osteopenia. Fracture risk increases approximately 1.5 to 2.5 times for every one standard deviation below normal. Women in the lowest BMD group have 8.5 times the risk of fracture compared to those in the highest density group (Lancet 341:72, 1993). The gradient of risk of fracture is continuous and it is not possible to define a cut off point below which fractures will occur and above which they will not.
. With new profitable drugs on the market the pharmaceutical industry is pressuring the scientific and medical communities to increase therapy for osteoporosis. One part of this commercial campaign is to simplify the treatment decision for women by use of a BMD value of -2.5 SDs (Ann Intern Med 125:623, 1996). However, the matter of treatment is not so simple. Specific bone mineral cut offs alone are not indications for treatment; most authorities believe other criteria--such as age, tendency to fall, and previous fractures-- must also be considered both for starting therapy and monitoring the effectiveness. A single low BMD measurement should not be the sole criteria to start treatment.
. BMD testing is big business. Money is made by the doctors, clinics, and hospitals who own the BMD testing equipment. Manufacturers of the equipment also have a strong financial incentive for women to get BMD testing. However, the biggest promoter of testing are the drug companies, such as Merck & Co. who sell Fosamax. These financial interests have introduced programs for testing healthy women at places of business and in shopping malls. The efforts are to create a market for their equipment and drugs. It is often stated in scientific articles that BMD should be used for screening because the results are just as good as using cholesterol levels to predict heart attacks and blood pressure to predict strokes. All of these screening programs have been used primarily to increase the market share for the pharmaceutical and medical businesses. Furthermore, these three diseases also have in common their origin and treatment limitations: they are all due to the rich western diet and the drug therapies are of limited effectiveness with high costs and many serious side effects.
. BMD is only one of many risk factors that predict an osteoporosis related fracture in women; others with similar predictive value are a history of maternal hip fracture, weight loss since age 25, and standing for less than 4 hours a day--all of this data requires no expensive tests to obtain (N Engl J Med 332:767, 1995). Dr. Deborah Marshall of the Swedish Council of Technological Assessment in Health Care wrote in the August 31, 1996 issue of the Lancet, "There are no data from controlled clinical trials about the consequences of screening by measuring BMD in terms of fractures averted, although trials are in progress in Britain and Sweden. Furthermore, it is not enough to identify individuals correctly as being at high risk: one must also be able to treat those identified with effective treatments. There are currently too many unanswered questions about available treatments--including their effectiveness in terms of preventing fractures, compliance rates, and the loss of benefit after treatment is stopped--to justify endorsing a screening programme." (313:561).
. The case for screening (checking large numbers of healthy women) at menopause is not strong, and the consensus view is population based screening cannot at present be justified. Also concerning for our health-cost-conscious country is that it would cost $6 billion to "screen" every woman in the US near menopause for BMD. Health care providers interested in cost effectiveness are waging a war on those purely interested in the profits of medicine.
. Assessment of bone mass is justified in those cases in which the results obtained will influence decisions about the treatment, and for monitoring bone loss caused by disease. Such indications for BMD tests might include:
When BMD should not be used:
Consideration must be given to the potential risks and harms of screening; such as "labeling" a person with a disease (osteoporosis), causing anxiety and distress; discrimination for employment and health and life insurance; and dependency on medications with serious side effects.
Check the accuracy of this information with your doctor before
applying information in this newsletter to your health care. Don't
change your diet or medication without your doctor's advice.
John McDougall, M.D.
If you would like to read more about Monitoring & Enhancing
Bone Building or the other articles in this issue:
Preparation Time: 15 minutes
Cooking Time: 20 minutes
Hint: Chop the swiss chard in a food processor to save time.
The other Recipes are:
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