Low Bone Mineral Density and Risk of Fracture in White Female Nursing Home Residents.

Low Bone Mineral Density and Risk of Fracture in White Female Nursing Home Residents Chandler JM, Zimmerman SI, Girman CJ, et al (Department of Epidemiology, Merck Research Laboratories, Blue Bell, Pa; Department of Epidemiology and Preventive Medicine, University of Maryland at Baltimore; Department of Diagnostic Radiology, University of Maryland Medical Center, Baltimore, Md; Cecil G Sheps Center for Health Services Research, School of Social Work, and Department of Family Medicine, University of North Carolina, Chapel Hill, NC), JAMA. 2000;284:972-977.

The rate of hip fracture among female nursing home residents who are white is almost 10 times higher than in community-dwelling elderly persons. Research has established that low bone mineral density (BMD) is a strong predictor of fracture in community-dwelling women who are white but that relationship has not been clearly investigated among female nursing home residents who are white. This study investigated the relationship between low BMD and risk of fracture in nursing home residents.

Subjects were 1,456 women who were white, 65 years of age or older, and resided in any of 47 randomly selected licensed, long-term nursing facilities in Maryland. Of these subjects, 89 residents (6.2%) were taking medications for osteoporosis and 43 residents (3%) had a history of fracture in the past 6 months. Baseline measures were collected between April 1995 and June 1997. The researchers assessed BMD at the distal radius of the dominant arm using a DTX-100 single x-ray absorptiometer. Demographic data were collected as well as functional, cognitive, psychosocial, and medical status from the Minimum Data Set (MDS).

During the 18 months after baseline examination, the medical records of all participants were reviewed and osteoporotic fractures that were documented by a physician were counted. The mean BMD and standard deviation (SD) of the full cohort of subjects were 0.302 [+ or -] 0.07 g/[cm.sup.2], which came to 3.5 SDs below the normal mean for young women. Eighty-two percent of residents had a BMD 2.5 SDs lower than the normal mean, and 54% had values that were 3.5 SDs lower than the normal mean. A total of 223 osteoporotic fractures occurred among 180 women, 38% of which were hip fractures.

For each decrease of one SD in BMD, fracture risk increased 40%. Transfer independence was also found to be a strong, independent predictor of fracture risk. Together, the strongest predictors of fracture were low BMD and independence in transfer. These predictors operated synergistically to increase fracture risk. In this way, for a resident with very low BMD, who was also independent in transfers, the risk of fracture more than tripled. Among residents who required assistance with transfers, those with the lowest BMD levels had a 60% higher risk of fractures than those with higher BMD levels. The authors speculated that residents who were independent in transfers may have had greater opportunity to fall than those requiring assistance, because many fractures occurred during transfer activities. Higher BMD may have protected some failers against fracture.

According to the authors, few residents were receiving osteoporosis medication at baseline, and information about medication use during follow-up was unavailable during this study. Therefore, the authors believed that their estimates of the BMD-fracture risk relationship may be conservative because including those residents who were being treated for low BMD might affect the estimate. The authors suggested further study to determine whether interventions to increase BMD will lower the fracture rate among nursing home residents.

Sondra E Dunkle, PT, EdD Pocatello, Idaho