Jan. 18, 2012 -- Women with normal or nearly normal bone density at age 67 may not need repeat testing for about 15 years, according to a new study of nearly 5,000 women.
If bone density was normal or nearly so at the study start, "only 10% developed osteoporosis over 15 years,'' says study researcher Margaret Gourlay, MD, MPH, assistant professor of family medicine at the University of North Carolina, Chapel Hill. "Their bone density was very stable."
Osteoporosis is a leading cause of dangerous and painful fractures. A routine bone density test is recommended for women at age 65. However, guidelines are vague about how often to repeat the test, Gourlay tells WebMD. She says the new research will provide guidance for organizations that make such recommendations.
Not everyone agrees. An interval of 15 years is too long, says Felicia Cosman, MD, senior clinical director for the National Osteoporosis Foundation, who reviewed the study for WebMD. She cites flaws in the study design.
The study is published in The New England Journal of Medicine.
''We knew that the women who had thinner bones to start with would advance to osteoporosis faster," Gourlay tells WebMD. "The new thing we showed was a clear difference between low-risk and high-risk groups and how rapidly they developed osteoporosis."
The women were enrolled in the Study of Osteoporotic Fractures in 1986-1988, when they were aged 65 or older. They had bone density testing about two years later.
After excluding some women for various reasons -- such as having osteoporosis already or a history of fractures -- almost 5,000 women were placed into one of four groups depending on their bone density. The four groups included:
The women were followed for up to 15 years. They had two to five repeat tests.
The researchers took into account major risk factors, such as age, weight, and smoking.
The researchers estimated the time it would take for 10% of the women in each group to progress to osteoporosis. They concluded that osteoporosis would develop in:
About 15 years for those with either normal bone density or mild osteopenia
About five years for those with moderate osteopenia
About one year for those with severe osteopenia.
The study was funded by the National Institutes of Health.
The results may help women and their doctors decide how often to re-test, Gourlay says, and the findings only apply to postmenopausal women age 67 and over.
Bone Density Testing: Perspectives
The study provides valuable information to doctors and patients, says Robert A. Adler, MD, chief of endocrinology at the McGuire Veterans Administration Medical Center. He is also professor of internal medicine and epidemiology and community health at the Virginia Commonwealth University School of Medicine, Richmond. "Doctors haven't really known how soon to re-measure bone density."