Press Releases for 1995

NATIONAL INSTITUTES OF HEALTH
March 22, 1995
Contact: Elia Ben-Arii
Office of Scientific and
Health Communications
(301) 496-8188

Researchers Identify Multiple Hip Fracture Risk Factors, Steps to Reduce Risk

A host of readily identifiable factors, many of which can easily be modified, increase the risk of hip fracture in older women, according to researchers participating in the Study of Osteoporotic Fractures (SOF). The study, funded by the National Institutes of Health (NIH), involves more than 9,500 women aged 65 and older and suggests that there are a number of steps women can take that may decrease their fracture risk. These include staying active, walking for exercise, getting treatment for impaired vision, quitting smoking, stopping use of certain medications, reducing caffeine intake, maintaining body weight and taking steps to maintain bone density, including estrogen replacement therapy or other treatments.

The researchers found that women who have five or more risk factors have an especially high likelihood of suffering a hip fracture. Previous results from this group and others show that women with low bone density have a greater risk of hip fracture. This new study finds that assessing risk factors in addition to bone density further improves the ability to predict a woman's risk.

The results are reported in the March 23, 1995 issue of The New England Journal of Medicine by Steven R. Cummings, M.D., of the University of California, San Francisco (UCSF), and his colleagues at UCSF and four participating clinical centers in Baltimore, Md., Minneapolis, Minn., Pittsburgh, Pa., and Portland, Ore. SOF is a multicenter study in which over 9,500 white women aged 65 and above and not living in nursing homes have been participating for 6 to 8 years to help understand who is at risk for hip fracture. The study is supported by grants from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) and the National Institute on Aging (NIA), components of the NIH.

"The finding that there are many things that a woman can do on her own that may decrease her risk of hip fracture is extremely important," says Michael D. Lockshin, M.D., the acting director of NIAMS. "Also important is the idea that in the future it may be possible to identify specific women-and perhaps men-who are at especially high risk for hip fracture, and target them for intensive prevention efforts."

"Avoiding hip fracture is a life and death issue for many older people. It's a devastating injury," says Richard J. Hodes, M.D., director of the NIA. One of every six white women will have a hip fracture during her lifetime. Of the more than 250,000 people each year who have hip fractures, up to 20 percent will not survive more than a year. Of those who do survive, many are left unable to walk and are forced to enter a nursing home. "Focusing on the prevention of hip fractures is an important element in our efforts to promote independence and an enhanced quality of life for older people," says Hodes.

Researchers at the four participating clinical centers did tests for bone density and assessed other potential risk factors through physical examinations, questionnaires and interviews in 9,516 older women who had no previous hip fracture. They contacted these women at 4-month intervals for an average of 4.1 years to determine the frequency of hip fracture.

The SOF investigators identified 16 independent factors besides bone density that increased the risk of hip fracture in older women; some of these risk factors have been identified previously in less comprehensive studies. The effect of most individual risk factors was modest, but together their impact was substantial. Fifteen percent of the women in the study had five or more risk factors (not including low bone density); these women had an 18 times greater occurrence of hip fractures than the 47 percent of women with two or less risk factors. "A very small number of women with a lot of the risk factors plus low bone density account for most of the fractures," Cummings says. "The six percent of women who had five or more risk factors in addition to low bone density accounted for one-third of the 192 hip fractures we observed during the study period."

Because many of these risk factors can be identified by a simple physical examination and patient interview, they can provide health-care practitioners with valuable and easily obtained information that can help identify those older women who most urgently need to take steps to reduce their fracture risk.

Cummings and colleagues found that a woman whose mother suffered a hip fracture has twice the risk of hip fracture, and that this risk factor is independent of a woman's bone density. "Everyone has believed that family history is important, but this is the first time anyone has shown that it is in fact important and just how important it is," says Cummings. "What's surprising is that if your mother broke her hip, you're at higher risk of breaking your hip regardless of what your bone density is." Cummings emphasized, however, that "although you can't change your family history, you can reduce your risk in other ways. Taking precautions to reduce the risk of hip fractures is even more important for those with a family history."

In addition to women whose mothers had suffered a hip fracture (especially before age 80), women who were tall at age 25 and women who weighed less than they had at age 25 also had an increased risk of hip fracture. The more weight a woman had gained since age 25, the lower her risk of hip fracture. However, Cummings notes, "gaining weight is bad for your heart, and heart disease, not hip fracture, is the number one killer of women." As for the negative effects of losing weight, Cummings explains: "Weight loss can be a sign of underlying illness. The decline in weight could also indicate loss of muscle that makes a woman more prone to falling." The higher risk for taller women may be because when they fall they fall harder or because of differences in the geometry of their hip bones that may affect fracture risk.

Other factors that increased the risk of hip fracture were poorer health as rated by the women themselves, a history of hyperthyroidism, a history of any other fracture since age 50 and therapy with anticonvulsants or certain long-acting medications commonly taken for anxiety or insomnia. As caffeine intake increased, so did the risk of hip fracture. Women who spent less than 4 hours a day on their feet had twice the risk, while women who regularly walked for exercise had a 30 percent lower risk of hip fracture. Risk tended to decrease as the distance walked per day increased. Smoking was also a risk factor, probably because smoking limits normal weight gain and has adverse effects on health, physical fitness and exercise patterns.

Four observations that were made by physical examination indicated an increased risk of hip fracture: inability to stand from a chair without using one's arms, a resting pulse rate of more than 80 beats per minute, poor depth perception and reduced ability to perceive visual contrast. Being unable to stand up from a chair without using your arms means you are more likely to fall, and doubles your risk of hip fracture. The increased risk due to vision problems suggests that treating or preventing eye conditions such as cataracts, diabetic retinopathy and glaucoma may help prevent hip fractures. Lower bone density also increased the risk of hip fracture, as has been shown in many previous studies.

The researchers also identified a number of factors that were not associated with increased risk of hip fracture. Cummings says some of these results were surprising: "This study does not support widely held beliefs that fair hair color, northern European ancestry, earlier natural menopause or use of aluminum-containing antacids are associated with an increased risk of hip fracture," he says. In addition, in contrast to other studies, results of this study indicate that moderate alcohol intake does not increase hip fracture risk. A history of breast feeding also did not increase risk.

The results were consistent with the view that estrogen therapy protects against hip fracture, although the small number of women taking estrogen limited the strength of these results. However, another study from this group has found that current and long-term use of estrogen reduces the risk of hip fracture.

"The most important thing about this study is that it points out the importance of risk factors besides bone density in the cause of hip fractures," says Cummings. "This is complicated, and bone density clearly plays a role, but so do other factors about the health of the whole woman."

The coordinating center for SOF is at UCSF, and the four clinical centers are at the University of Pittsburgh, in Pennsylvania; the Kaiser Permanente Center for Health Research, in Portland, Oregon; University of Maryland at Baltimore; and University of Minnesota, Minneapolis. Nearly 100 investigators are involved in this study.

The National Institute of Arthritis and Musculoskeletal and Skin Diseases, in collaboration with other Institutes and agencies, including the National Institute on Aging, leads and coordinates the Federal biomedical research effort in bone and musculoskeletal disease. The Institute supports research projects, research training, clinical trials, and epidemiologic studies, and disseminates information on research results.

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Reference : Risk factors for hip fracture in white women. Steven R. Cummings, M.D., Michael C. Nevitt, Ph.D., Warren S. Browner, M.D., M.P.H., Katie Stone, M.A., Kathleen M. Fox, Ph.D., Kristine E. Ensrud, M.D., M.P.H., Jane Cauley, Dr.P.H., Dennis Black, Ph.D., and Thomas M. Vogt, M.D., M.P.H., for the Study of Osteoporotic Fractures Research Group, The New England Journal of Medicine , March 23, 1995.

Contact Information:

For further information, including other researchers available for comment, contact:

NIAMS media contact: Elia Ben-Ari (301) 496-8190
NIA media contact: Vicky Cahan (301) 496-1752
UCSF media contact: Rebecca Higbee (415) 476-2557