When you’re assessing older women for the risk of hip fracture, renal dysfunction is a red flag.

That’s the message from a multi-center study of 300 randomly selected women aged 65 and older who experienced fractures during a six-year follow-up period. The women lived in Portland, Ore., Monongahela Valley, Pa., Baltimore, and Minneapolis. When researchers compared the subjects to age-matched controls who had normal or near-normal kidney function (an estimated glomerular filtration rate [eGFR] of ≥60 mL/min/1.73 m2), those with an eGFR of 45-59 had a 57% increased risk of hip fracture; women with an eGFR <45 had a twofold higher risk.

The risk of trochanteric fracture was particularly pronounced:
seven times higher in women with an eGFR of <45 and four times higher in those with an eGFR of 45-59, compared with women who had a higher eGFR. Even after further adjustment for diabetes, health status, smoking, history of falls, and exercise, the risks were 5.0 and 3.7 times higher, respectively.

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Risk of femoral neck fracture did not differ significantly by eGFR. Nor was renal function associated with vertebral fracture. No other types of fractures were studied.“Abnormalities in phosphorus, calcium, and vitamin D metabolism that occur even in mild renal insufficiency may result in decreased formation of 1,25-dihydroxyvitamin D by the kidney, leading to decreased fractional calcium absorption, secondary hyper-parathyroidism, greater bone resorption, and increased risk of hip fracture,” the investigators speculated (Arch Intern Med. 2007;167:133-139).

“Our findings suggest that clinicians should consider renal function as part of the risk assessment for hip fracture in elderly women,” the authors concluded.