Dr Shu-Hung Wang, of the Taipei Veterans General Hospital, and his colleagues evaluated nearly 15 000 adults, 90% of them were woman that had lupus. They followed them for an average of six years.
During that time, 75 suffered a hip fracture. Of those, 57 were cervical fractures of the hip; the other 18 were trochanteric fractures of the hip.
"Anatomically, cervical hip fractures involve the [uppermost area of the thighbone]," said Dr Shu-Hung Wang, a rheumatology fellow at the hospital and a co-author of the study. "Trochanteric hip fracture occurs between the lesser and greater trochanters." Trochanters are the bony prominences near the end of the thighbone.
The researchers compared the women and men with lupus to the same number of healthy people without lupus. In the healthy group, 43 had hip fractures during the follow-up period, and they were evenly divided between the two types.
Confidence in numbers
Having lupus, the researchers concluded, raised the risk for cervical fractures compared to the general population, but not for the other fracture type. And women with lupus got cervical fractures at younger ages, the researchers said.
Not enough men were included in the study to do a scientific analysis of their fracture risk.
The study, which didn't prove that lupus leads to hip fractures, appeared online recently in the journal Arthritis Care & Research.
The number of people studied lends strength to the findings, said Dr David Pisetsky, a professor of medicine at the Duke University School of Medicine and a member of the scientific advisory board for the Lupus Research Institute. Pisetsky reviewed the findings but was not involved in the study.
"When you get 15 000 [subjects], you get confidence in the numbers," he said.
The higher risk of hip fracture is not surprising, due to the nature of the disease, he said. Lupus involves a malfunction of the immune system. Normally, the immune system makes antibodies in response to invaders; in lupus, the body can't differentiate invaders from normal tissue, so it makes autoantibodies that turn on the body, attacking normal tissue.
The autoantibodies cause inflammation, pain and damage to the body.
"The systemic inflammation affects bone," Pisetsky said. Patients often are prescribed steroid medicine to relieve the inflammation, but the medicines can also affect bones adversely, he said.
Although the risk to bones in lupus patients is known, the new study teases out details on the type of fracture risk, Pisetsky said.
Treatments, especially the steroids, can affect the bones, said Dr Joan Merrill, medical director of the Lupus Foundation of America and chairwoman of the clinical pharmacology research program at the Oklahoma Medical Research Foundation. "Steroids are also associated with increased risk for osteonecrosis [death of the bones], which literally can cause the hip joint and other joints to collapse," she said.
For those reasons, experts in recent years have been focusing on using the lowest dose possible of steroids to control symptoms, Pisetsky said.
To help preserve bone health, Pisetsky tells his lupus patients to get enough calcium and vitamin D and to take bone-maintenance drugs, if their doctor decides they are necessary.
Getting regular exercise can help too, he said. With age, lupus patients should try to preserve their balance, which can also reduce the risk of falls.
Study co-author Wang reported serving on advisory boards and receiving honoraria for speaking from several pharmaceutical companies. The study was funded by the Taiwan National Science Council, Taipei Veterans General Hospital and other institutions.
To learn more about lupus, visit the Lupus Foundation of America.