Breaking a bone is frequently a catastrophic injury for an older patient. A hip fracture or a vertebral fracture frequently leads to a permanent decrease in mobility which starts an inexorable decline in health and independence. For that reason, fracture prevention is a critical part of the care of older people.

Osteoporosis, which is severely decreased bone density, is a major risk factor for fractures, especially in women over 65. Osteoporosis is also treatable, and there is good evidence that treating osteoporosis with bisphosphonates (a family of medicines which includes Fosamax, Actonel, and Boniva) prevents fractures.

So we know that testing bone density is important in women over 65. But we don’t know how frequently we should be recommending the test. Medicare pays for the test every two years, and in the absence of scientific information about how frequently the test is valuable, that has become the accepted default.

This week’s New England Journal of Medicine published a study that helps shed some light on the question. Almost 5,000 women 67 years of age older who did not have osteoporosis at the beginning of the study were enrolled. The women had periodic bone density studies for up to 15 years. The goal of the study was to find the length of time between tests that would safely detect most cases of osteoporosis before a fracture occurred.

Not surprisingly the safe testing interval depends a lot on the initial bone density. For women with advanced osteopenia*, a testing interval of only 1 year was required to detect osteoporosis in time. For women with moderate osteopenia, retesting in 4 years was adequate. Women with mild osteopenia or normal bone density could wait 15 years before the next test. The intervals also varied with the age of the women, with younger women losing bone density more slowly than older women.

These findings should be validated in large studies before put to use. But if the general theme is right, women in their 60s with normal bone density can safely defer their next test for a decade.

Learn more:

Patients With Normal Bone Density Can Delay Retests, Study Suggests (NY Times)
Many Older Women May Not Need Frequent Bone Scans (Shots, NPR’s health blog)
How Often Should Women Be Screened for Osteoporosis? (Wall Street Journal health blog)
Bone-Density Testing Interval and Transition to Osteoporosis in Older Women (New England Journal of Medicine article)
Medications for Osteoporosis (my summary in 2008)

* Definition of various levels of bone density according to T score
Bone Density            T score
Normal                          greater than -1
Mild osteopenia            between -1 and -1.5
Moderate osteopenia   between -1.5 and -2
Advanced osteopenia   between -2 and -2.5
Osteoporosis                  less than -2.5