The study is published in the August 23rd issue of the Journal of the American Medical Association (JAMA).
The study, conducted by the University of Maryland School of Medicine in Baltimore, found that the women who had bone density levels below the nursing home average were more than twice as likely to suffer a fracture than women with higher than average bone density levels. The risk was more than three times greater for residents with low bone density who also had the ability to move around independently.
"Activity is good, but nursing home residents with better mobility are also more vulnerable to falls," says Sheryl Zimmerman, Ph.D., the lead investigator of the study who is now associate professor of epidemiology and social work at the University of North Carolina. "Mobility and low bone mineral density work together to dramatically increase the risk of fracture," says Dr. Zimmerman, who is also co-director of the Program on Aging at the Sheps Center for Health Services Research.
The study involved more than 1,400 white women from 47 randomly selected nursing homes throughout the state of Maryland. Researchers found that 80 percent of the women had osteoporosis, which means that they had low bone mineral density and weak, brittle bones. The women with the lowest levels of bone density had the greatest fracture rates.
"Hip fractures are a very debilitating injury for elderly nursing home residents," says Jay S. Magaziner, Ph.D., professor of epidemiology and director of the division of gerontology in the Department of Epidemiology and Preventive Medicine at the University of Maryland School of Medicine. "A quarter of those who suffer a hip fracture die within a year, and more than half of the survivors never regain the level of functioning they had before the fracture," says Dr. Magaziner, a co-author of the study.
Using a van equipped with special equipment to test bone mineral density, researchers from the University of Maryland's division of gerontology traveled to area nursing homes to measure bone density in the arms of study volunteers. Eighteen months later, they reviewed the medical records of the participants to determine the number of new fractures. A total of 223 osteoporosis-related fractures occurred among 180 women in the study (some women had more than one fracture). Seventy-percent of the fractures resulted from falls.
The study focused on white women because this group comprises two-thirds of the U.S. nursing home population, and the incidence of osteoporosis-related fractures is highest among elderly white women. All of the women who volunteered for the study were over age 65.
"Nursing home fractures are often associated with frailty and illness, but bone mineral density is not always considered to be an important factor," says Julie M. Chandler, Ph.D., associate director in the epidemiology department at Merck Research Laboratories. "Our research shows that bone mineral density is a main contributor to the fracture risk in nursing homes," says Chandler, the lead author of the study.
The researchers hope the data will help doctors and caregivers prevent fractures among nursing homes residents. "In addition to evaluating a resident's bone strength, we should also consider their level of activity," says Dr. Magaziner. "Although further study is needed, medications and dietary supplements to improve bone density or prevent bone loss may offer some protection. Patients who are more mobile may benefit from exercises to improve strength and balance and reduce the risk falling."
The study was funded by grants from Merck Research Laboratories and the National Institute on Aging.
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