WASHINGTON, June 25 (Reuters) - Two studies published on Monday added to the growing evidence that the most popular class of drugs taken to treat depression may contribute to fragile bones in elderly people.
The research focused on a class of antidepressant drugs called selective serotonin reuptake inhibitors. Millions of people, including many elderly, take these drugs, known as SSRIs, which include Eli Lilly and Co's Prozac, known generically as fluoxetine.
Two teams of researchers found that older men and women taking SSRIs had more bone loss than those not taking the drugs, which account for more than 60 percent of U.S. antidepressant drug prescriptions. A drop in bone mass can lead to osteoporosis and bone fractures.
A team led by Dr. Susan Diem of the University of Minnesota tracked 2,722 women, average age 78, including 198 SSRI users. They measured their bone mineral density five years apart.
Those taking the antidepressants experienced a density decrease at the hip of 0.82 percent per year, compared to 0.47 percent per year among those not taking them, the study found.
"We found that SSRI use was associated with increased rates of bone loss in this group of older women," Diem said in a telephone interview.
"But our research cannot definitively determine whether the SSRIs are the cause of the increased rates of the bone loss or whether the increased rate is due to other differences between SSRI users and nonusers," Diem added.
Diem noted, for example, that users of these drugs may be less physically active than people not using the drugs.
"I don't want people stopping their antidepressants for these results. These are all preliminary findings," Diem said. "However, I think our findings suggest that this area needs to be further looked at."
In the second study, researchers led by Dr. Elizabeth Haney of Oregon Health & Sciences University in Portland tracked 5,995 men, average age 74, including 160 who used SSRIs. Bone mineral density at the hip was 3.9 percent lower among SSRI users and 5.9 percent lower in the spine in than men not taking antidepressants, the study found.
Haney's team compared other antidepressants and found no apparent effects on hip or spine density measurements between men who took tricyclic antidepressants or a third type of antidepressant called trazodone and those who took no antidepressants.
The studies, published in the journal Archives of Internal Medicine, did not look at fracture risk.
But another study by researchers from McGill University in Montreal, published in January, found that older adults taking these drugs had double the risk of a bone fracture compared to those not taking the drugs.
SSRIs inhibit a protein that transports serotonin, a chemical messenger involved in sleep and mood. The protein has been discovered in bone as well, raising the possibility these drugs may affect bone strength, the researchers said.
