To hear Sally Field tell it, reversing bone loss with the drug Boniva is important because you have only “one body and one life.” And the 63-year-old actress—who looks around 45 in commercials for the bone-building drug—implies that many, if not most, healthy and fit middle-aged women are on the road to osteoporosis.

They’re not.

According to the National Osteoporosis Foundation, about 10 million Americans have osteoporosis, 80 percent of them women, but an additional 34 million have “low bone mass” that puts them at increased risk. Sally Field is in the former group, but many women in the latter category, experts contend, are being unnecessarily treated with bisphosphonate drugs like Boniva, Fosamax, or Actonel.

“These ads blur the line between those who have moderate and severe risk factors for osteoporosis,” says Lisa Schwartz, an associate professor of medicine at the Dartmouth Institute for Health Policy and Clinical Practice. “The majority of bad fractures occur at the end of life, often in a woman’s late 70s.”

Losing some bone mass as you age is normal: Women lose an average of 2 to 7 percent of their bone mass every year during the first few years after the onset of menopause, which can pose problems if they start out with low bone mass to begin with. Doctors often do bone density scans in 50-something women, especially those who have a family history of osteoporosis, to determine whether they need to be on bisphosphonate drugs. (The U.S. Preventive Services Task Force recommends a bone density test at least once for all women ages 65 or older.)

A scan measurement of -2.5 or lower indicates osteoporosis, which requires frequent monitoring, lifestyle changes like weight lifting, supplements of vitamin D and calcium, and—often—treatment with a bisphosphonate drug. A scan measurement above -1 means normal bone mass and very low risk of osteoporosis. A reading of -1 to -2.5, however, indicates osteopenia, a “gray area” that doesn’t necessarily mean a future diagnosis of osteoporosis, says Bess Dawson-Hughes, director of the bone metabolism laboratory at Tufts University in Boston (who receives consulting fees from bisphosphonate manufacturers). “We shouldn’t imply that people in this intermediate zone have a disease,” she says. “Some with low bone mass will go on to develop osteoporosis, but some will not.”

To help better guide women (and men) with low bone mass, Dawson-Hughes two years ago chaired the National Osteoporosis Foundation’s committee to develop new guidelines. The foundation, which gets significant funding from pharmaceutical manufacturers, recommended that doctors calculate a 10-year fracture risk, using bone density testing as well as certain clinical factors, to determine whether to put patients on drugs. Those with a hip fracture risk of 3 percent should consider treatment, as well as those with a 20 percent or greater risk of having other fractures. Anyone with a previous hip or spine fracture or who has a bone density reading of -2.5 or less should also be treated. (The old guidelines, based on research only in postmenopausal white women, recommended treatment with a density reading of less than -2.0 or if women had low bone mass and one or more risk factors like smoking or the use of corticosteroid drugs.)

If doctors follow the new guidelines, says Dawson-Hughes, they will wind up treating fewer younger women with bisphosphonates. In an August study, she and her colleagues calculated that fewer than 10 percent of women in their 50s should be treated with bone-building drugs, compared with 42 percent who would have qualified under the old guidelines. Just 18 percent of women in their 60s would be eligible, compared with nearly 60 percent of 60-year-olds under the old guideline. On the other hand, she says, “slightly more” women in their 70s and 80s would qualify for the medications under the new guidelines since they’re more likely to experience crippling and often life-shortening fractures. (Bone-building drugs can cut the incidence of fractures in half for those with osteoporosis.)

While the new guidelines took into account the costs and benefits of treatment and the risks and costs of experiencing fractures, says Dawson-Hughes, they didn’t factor in the side effects associated with these drugs. Bisphosphonates can cause gastrointestinal upset and a rare condition in which part of the jaw bone dies; this is estimated to occur in 1 in 10,000 to 1 in 100,000 patients but is more likely in breast-cancer patients who are put on high doses (since research suggests it lowers their risk of recurrence). For this reason, dentists are often reluctant to perform extensive dental work on those taking bisphosphonates; any bone that’s exposed may not heal properly.

It’s also important to realize that no one knows the long-term effects of taking bone-building drugs for 20 or 30 years. Fosamax, the first bisphosphonate, was approved in 1995. Some experts worry that while the drugs slow down bone loss, they may also slow down remodeling, the process of the bone healing itself from tiny injuries caused by, say, exercise or daily activities. It could be that the drugs subtly change bone structure, though “the concern is conceptual at this point,” says Dawson-Hughes.

Unfortunately, too many doctors are probably still overmedicating low-risk women with osteopenia. If you get a bone density scan and fall into this gray area, make sure your doctor calculates your 10-year fracture risk to help guide your decision about going on medications.

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