Low Bone Mineral Density Often Goes Undetected

Source: Tufts University
February 8, 2002 (Reviewed: February 22, 2004)

Almost 50% of postmenopausal women in the United States have undiagnosed osteopenia or osteoporosis, according to the National Osteoporosis Risk Assessment (NORA) Study. That was among the findings recently published in the Journal of the American Medical Association.

The NORA Study

NORA, a longitudinal observational study, enrolled more than 200,000 subjects between September 1997 and March 1999. It included approximately 12 months of follow-up of this large group of postmenopausal women. None had prior diagnoses of osteoporosis and none had undergone bone mineral density (BMD) measurement within the previous 12 months.

Participants completed detailed questionnaires on personal and family history of fractures, diet and lifestyle, and medication use. Each volunteer also had a peripheral BMD measurement taken either in the forearm, using peripheral DXA (pDXA); the finger, using pDXA; or the heel, using either single x-ray absorptiometry (SXA) or ultrasonography. After 12 months, volunteers completed a follow-up questionnaire and noted any new fractures.

The World Health Organization's definition of low BMD was used in the study. Measurements that scored between 1 and 2.5 standard deviations (SD) below the average for the reference population were classified as osteopenia, while measurements 2.5 SDs or more below average were considered to be evidence of osteoporosis.

Predictable predictors

Approximately 40% of the women had osteopenia and about 7% had osteoporosis, according to the WHO standards. Aging was the strongest predictor of BMD, independent of all other risk factors. The odds of osteoporosis increased from 1.79 (95% CI, 1.56 -- 2.06) for women 55 to 59 years old to 22.56 (95% CI, 19.82 -- 25.67) for women ages 80 and older. Other characteristics that increased the likelihood of osteoporosis included poor health, personal history of fracture, maternal history of osteoporosis, and maternal history of a fracture after age 45.

Compared with white women, osteoporosis risk was slightly higher in Asian women (odds ratio = OR, 1.56) and Hispanic women (OR, 1.31), while African-American women were at less risk (OR, 0.55). Increasing body mass index (BMI) decreased osteoporosis risk (OR, 0.27 for BMI 26.00 -- 29.99 compared with BMI <23). Other protective factors were exercise, estrogen and diuretic use, and, somewhat surprisingly, consumption of alcoholic beverages.

This is the largest study of postmenopausal osteoporosis conducted in the United States thus far and the findings are consistent with those of smaller studies showing that more than 50% of women over age 50 have a low BMD. It also offers further support of previously-noted risk factors such as low BMI, physical inactivity, age, history of fractures, and smoking.

No diagnosis means no treatment

Of note is that even at baseline, 11% of the women reported having at least one fracture of the wrist, rib, hip, or spine after age 45. The researchers felt that this was most likely a consequence of osteoporosis that had not yet been diagnosed, and as a result, the appropriate treatment had not been started.

An editorial accompanying this article explains that many doctors and researchers have long suspected that "a significant number of postmenopausal women in primary care practices have clinically significant low BMD" and that such women are at increased risk of fracture within one year. The results of this study indicate that peripheral DXA can identify many of these women. The availability of this lower-cost alternative to central DXA may mean that more women can get BMD tests and, if necessary, begin preventive measures to ward off a fracture.

Source

• Identification and fracture outcomes of undiagnosed low bone mineral density in postmenopausal women. Results from the National Osteoporosis Risk Assessment. ES. Siris, PD. Miller, E. Barrett-Connor,  et al., JAMA , 2001, vol. 286, pp. 2815--2822

Related Links
An Occasional Drink May Aid Bone Strength
What are the Chances of Preventing Osteoporosis?
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