Moderate renal impairment raises the risk of hip fracture, particularly trochanter fracture, in older white women, reported Dr. Kristine E. Ensrud, and her associates in the Study of Osteoporotic Fractures.
“These findings suggest that clinicians should consider including renal function as part of the risk assessment for hip fracture in elderly women,” the researchers reported. An increased rate of hip fractures has been reported in patients with end-stage renal disease, those undergoing dialysis, and those who have received a renal transplant. However, this is the first longitudinal study of the link between hip fracture and mild to moderate renal insufficiency, according to Dr. Ensrud of the Veterans Affairs Medical Center, Minneapolis, and her associates.
They conducted a case-cohort study within the Study of Osteoporotic Fractures, a prospective study of over 9,700 women living in four U.S. regions that were aged 65 and older when enrolled in 1986–1988. The investigators assessed 149 white patients randomly selected from among those who sustained hip fractures during a mean follow-up of 6 years, and 377 without hip fractures.
A decreased estimated glomerular filtration (GFR) rate was significantly associated with an increased risk for hip fracture, even after the data were adjusted to account for traditional risk factors, the researchers reported (Arch. Intern. Med. 2007;167:133–9). In patients with a mildly decreased GFR the hazard ratio for hip fracture was 1.7, and in those with a moderately decreased GFR the hazard ratio was 2.3, compared with subjects who had a normal GFR.
Similarly, in subjects with a mildly decreased GFR the risk of trochanteric fracture in particular was increased nearly fourfold, and in those with moderately decreased GFR it was increased fivefold, compared with those who had a normal GFR. The underlying mechanisms for these associations are not yet understood. Abnormalities in phosphorous, calcium, and vitamin D metabolism occur in even mild renal insufficiency. And moderate renal dysfunction has been linked with increased inflammation, impaired coagulation, anemia, and malnutrition, Dr. Ensrud and her associates noted.
In an editorial comment accompanying the report, Dr. Stuart M. Sprague of Northwestern University, Chicago, said that “a staggering 19.2 million Americans, or 11% of the adult population,” currently have chronic kidney disease (CKD).
The study findings “are potentially very important, as they support the concept that a diagnosis of osteoporosis based on [bmd] criteria should not be made in patients with CKD and used as a predictor of fracture outcome,” Dr. Sprague wrote (Arch. Intern Med. 2007;167:115–6).