Q: I’m a woman in my mid-50s with a family history of
osteoporosis. How and when should I get screened for this
disease?
By the Faculty of Harvard Medical School
Q: I’m a woman in my mid-50s with a family history of osteoporosis. How and when should I get screened for this disease?
A: Osteoporosis is a bone-thinning disease that makes you more susceptible to breaking a bone. Each year, it’s responsible for more than 1.5 million fractures in the United States. While osteoporosis affects women much more often than men, it can occur in men, as well. In older adults, broken bones – especially in the hip, spine and wrist – can be very serious. They can lead to long-lasting pain and disability, sometimes even causing complications such as pneumonia and blood clots. That’s why screening tests that tell you if you have (or are likely to develop) osteoporosis are so important.
In the past, doctors could diagnose osteoporosis only after a person had already broken a bone. For many people, that diagnosis came too late to be of much use. Today, osteoporosis can be detected earlier with a bone mineral density (BMD) test.
BMD is the measurement of a bone’s mineral content. In general, the lower your bone density, the higher your risk for fracture. Usually, BMD is measured in the hip, spine or heel. To decide what levels place people at risk, experts looked at the bone densities of thousands of women and noted who had osteoporotic fractures and who didn’t.
Women who are in their 30s – when bone mass is at its peak – have the lowest fracture risk, so their average bone mass was used as the reference point. Researchers then determined the levels of bone density that were associated with a higher risk for osteoporosis. A number known as the T-score, which measures how far a bone-mass reading deviates from the average, defines whether a person has osteoporosis. The World Health Organization has established the following classification system:
n If your T-score is greater than -1: Your bone density is considered normal.
n If your T-score is -1 to -2.5: You have low bone mass (known as osteopenia), but not osteoporosis.
n If your T-score is -2.5 or less: You have osteoporosis, even if you haven’t yet broken a bone.
Several technologies can assess bone mass, but two (see illustration) have emerged as the most common. With dual energy X-ray absorptiometry (DXA), a machine sends X-rays through bones to calculate bone density. The process takes only 10 minutes and is simple: You lie on a table while an imager passes over your body. DXA is the most commonly used method of assessing BMD. It has emerged as the gold standard of BMD testing. DXA can compute the density of bone in any region of the body but requires only one-tenth of the radiation exposure of a standard chest X-ray.
Ultrasound, which uses sound waves to measure BMD at the heel, shin or finger, is increasingly being used as well. It does not give measurements as exact as those provided by DXA, but it seems to predict fracture risk. To measure BMD at the heel, you will be asked to place your bare foot in a device (known as a sonometer) that emits high-frequency sound waves. A computer determines the bone density by calculating how fast the sound waves pass through your heel. The machine can provide an estimate of your bone density in less than a minute. Lightweight and easy to use, this small device may make BMD measurements more accessible.
Currently, osteoporosis screenings are not given to everyone routinely. Experts are still debating who should receive them, because it’s not clear whether the benefits justify the cost of testing everyone. It’s best to talk to your doctor about whether testing is right for you. The National Osteoporosis Foundation recommends bone-density tests for all women age 65 and older and all postmenopausal women younger than 65 who have one or more risk factors for osteoporosis: having a family history of the disease, being thin and small-boned, taking glucocorticoid medications (often called steroids) and smoking.
Some men need osteoporosis screening as well. Men who have taken steroids or who have a history of broken bones should discuss screening with their doctors.
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