Jan. 24 (HealthDay News) -- Doing a follow-up bone mineral density (BMD) scan up to eight years after an initial scan doesn't improve doctors' ability to predict fractures in healthy older postmenopausal women, a U.S. study finds.

Currently, guidelines recommend the use of BMD measurements to screen for osteoporosis in women when they reach age 65. There's little evidence to support the use of repeat BMD testing in order to assess a woman's fracture risk, but repeat BMD scans are commonly performed in clinical practice, according to background information in the study.

Researchers at Kaiser Permanente Northwest/Hawaii, Portland, Ore., measured total hip BMD in 4,124 women (average age 72) in 1989 and 1990, and once again an average of eight years later. Between the first and second test the women lost an average of 0.59 percent of their bone mass per year.

After the repeat BMD test, the women were followed for an average of five years in order to record fractures. During that follow-up period, 877 women had a non-traumatic non-spine fracture (including 275 hip fractures) and 340 women suffered a spine fracture.

The study authors wrote that they "did not find any improvement in the overall predictive value in a second measure of BMD, obtained a mean (average) of eight years later, in prediction of hip, spine or overall non-spine fracture risk. In other words, the initial BMD was highly, and similarly, predictive of fracture risk in our (study) population."

Repeat BMD measurement may prove useful in some women, such as those with health conditions that contribute to rapid bone loss, or younger women in early menopause, the researchers noted.

"However, our results do suggest that, for the average healthy older woman 65 years or older, a repeat BMD measurement has little or no value in classifying risk for future fracture -- even for the average woman who has osteoporosis by initial BMD measure or high BMD loss," they concluded.

The findings were published in the Jan. 22 issue of the Archives of Internal Medicine.