Last year, AFP published the U.S. Preventive Services Task Force's updated recommendations on screening for osteoporosis, which advised dual-energy x-ray absorptiometry (DEXA) in "women 65 years or older and in younger women whose fracture risk is equal to or greater than that of a 65-year-old white woman with no additional risk factors." However, the USPSTF statement left one important question unanswered: when should a woman be re-screened if her first test shows normal or slightly decreased bone mineral density (BMD)? Put another way, what are the chances that a woman without osteoporosis today will develop it in the future?
A research team led by former AFP medical editor Margaret Gourlay, MD, MPH recently shed light on this question by following nearly 5000 U.S. women age 67 years or older with normal BMD or osteopenia for up to 15 years. They defined the BMD re-testing interval as the estimated time it took for 10% of women to develop osteoporosis before having a hip or clinical vertebral fracture. According to their report in the January 19th issue of the New England Journal of Medicine, more than 90% of women with initially normal BMD or mild osteopenia did not develop osteoporosis after 15 years. As might be expected, women with moderate and advanced osteopenia progressed faster, with 10% of each group developing osteoporosis after 5 years and 1 year, respectively.
This study's results have substantial implications for family physicians and their patients. In the absence of new risk factors for osteoporosis (e.g., significant weight loss, corticosteroid use), a woman with normal BMD at age 65 may not need to be re-tested until age 80, an interval that is substantially longer than current clinical practice. That's good news, since as Dr. Gourlay pointed out in a previous AFP editorial, many U.S. women who are at risk for osteoporosis have yet to receive any screening at all. Armed with this new information, family physicians and other primary care clinicians can now work to redirect testing resources to where they are needed most.