"Other studies have pointed to this [link], but our study confirms it," says David Goltzman, MD, one of the study's authors. Goltzman is director of the Centre for Bone and Periodontal Research at McGill University in Montreal.
The antidepressants studied are a class known as selective serotonin reuptake inhibitors, or SSRIs. It includes such drugs as Prozac and Paxil.
Low levels of the brain chemical serotonin are associated with depression, and the drugs are thought to work by making serotonin more available.
SSRIs and Fracture Risk
Goltzman and his colleagues evaluated 5,008 adults 50 and older; the average age was 65.
They followed them for more than five years to see if they experienced "fragility" fractures -- the type suffered from relatively minor traumas such as falling out of bed.
Daily use of SSRIs was reported by 137 participants.
Even after the researchers adjusted for factors known to increase the risk of fractures -- such as falls, low bone density, and physical inactivity -- the adults on SSRI antidepressants had twice the risk of fracture than those not on such antidepressants.
X-rays confirmed the self-reports of fracture.
"In the SSRI group, there were 18 X-ray confirmed fragility fractures out of 137 people, or 13.5%," says Goltzman.
"In the non-user group, there were 317 X-ray confirmed fragility fractures out of 4,871 people, or 6.5%," Goltzman says.
Five SSRIs were used by study participants; besides Prozac and Paxil, they used Celexa, Luvox, and Zoloft.
How SSRIs May Boost Risk
The antidepressants may boost risk of fracture, Goltzman says, because of their effect on bone physiology. Serotonin recently has been found to be important in bone physiology.
One animal study, for instance, found that "if you alter the ability of the bone to use serotonin, you will get a reduction in bone density," Goltzman says.
Pharmaceutical Company Weighs In
The study does not prove cause and effect, says Amy Sousa, spokesman for Eli Lilly and Company, the maker of Prozac.
"The current Prozac product label lists 'osteoporosis' as an adverse event occurring on a rare basis -- less than 1 in 10,000 patients, based upon data from clinical trials," she says.
Goltzman's study is a small one, she adds.
Funding for the study was provided by a variety of sources, including Eli Lilly Canada, other pharmaceutical companies, and the Canadian Institutes of Health Research.
Those over 50 should simply be aware of the link, Goltzman says, and perhaps get a bone density test if they are thinking of going on SSRIs.
"If you are over 50, and your doctor prescribes an SSRI, go have a bone density test first, especially if you have had a fracture from a minor trauma," he says. "I would not tell a patient not to take SSRIs."
Paying attention to other lifestyle measures known to reduce fracture risk, such as staying active, getting enough vitamin D and calcium, not smoking, and not drinking alcohol to excess, is also important, Goltzman says.
More research is needed, says Robert P. Heaney, MD, a professor at Creighton University in Omaha, Neb., and a long-time osteoporosis researcher. "Depression itself is related to fracture risk," he says.
The study findings, Heaney agrees, do not suggest people should stop taking SSRIs if their doctor has decided the drugs can help them battle depression.
Depression is especially common among older adults, Goltzman notes, affecting about 10% of older people.
Goltzman's study appears in the Jan. 22 issue of the Archives of Internal Medicine.
SOURCES: David Goltzman, MD, director, Centre for Bone and Periodontal Research, McGill University, Montreal. Goltzman, D Archives of Internal Medicine, Jan. 22, 2007; vol 167: pp 188-194. Robert P. Heaney, MD, John A. Creighton University Professor, Creighton University, Omaha, Neb. Amy Sousa, spokeswoman, Eli Lily and Company, Indianapolis.
By Kathleen Doheny
Reviewed by Louise Chang