PHILADELPHIA — The increased risk of hip fracture in women with lower bone mineral density mainly reflects an increased risk of nonsevere fracture rather than severe fracture, Jane A. Cauley, Dr.P.H., reported at the annual meeting of the American Society for Bone and Mineral Research.
Dr. Cauley, a professor of epidemiology at the University of Pittsburgh, looked for differences in risk factors for severe and nonsevere hip fractures using data from the longitudinal Study of Osteoporotic Fractures, involving 9,704 women aged 65 years and older.
The women were contacted every 4 months by postcard to determine if a hip fracture had occurred. The average follow-up period was 10.5 years.
Preoperative hip radiographs were obtained for 462 women—249 with femoral neck fractures and 213 with intertrochanteric fractures.
The fractures were rated by a single radiologist using the Garden and Kyle systems.
Most hip fractures were classified as severe. Of the femoral neck fractures, 70% were displaced. Of the intertrochanteric fractures, 72% were unstable.
For femoral neck hip fracture, women who went on to have undisplaced fractures had a femoral neck BMD about 7% lower than did women who had a displaced fracture. Among women in the lowest tertile for femoral neck BMD, 58% had displaced fractures, compared with 83% of women in the highest tertile for BMD.
Although lower femoral neck BMD was associated with a greater risk of both types of fracture, a one-standard-deviation decrease in BMD was associated with a more than threefold increased risk of having an undisplaced fracture. There was only an 86% increase in having a displaced fracture.
For intertrochanteric hip fracture, women who went on to have stable fractures had an intertrochanteric BMD about 7% lower than did women who had an unstable fracture. Among women in the lowest tertile for intertrochanteric BMD, 62% had unstable intertrochanteric fractures compared with about 80% of women with higher BMD, said Dr. Cauley.
Again, while low intertrochanteric BMD was associated with an increased risk of both types of intertrochanteric fractures, women with lower BMD had a threefold increase in the risk of having a stable intertrochanteric fracture, compared with an almost twofold increased risk of having an unstable fracture.
One standard deviation decrease in walking speed was a risk factor for femoral neck displaced and undisplaced fractures. A greater height at the age of 25 and steroid and alcohol use were associated with an increased risk for a femoral neck displaced factor.
Dr. Cauley disclosed that she has received research grants from Pfizer Inc., Novartis Pharmaceuticals Corp., Merck & Co, and Eli Lilly & Co. She also has received consulting fees from Novartis.