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Impaired Kidney Function Linked to Bone Loss


 

Impaired kidney function was associated with increased bone loss in an analysis of data from the population-based Canadian Multicentre Osteoporosis Study.

Among 635 study participants whose bone mineral density had been tested at baseline and at 5 years' follow-up, estimated creatinine clearance (eCCr) and estimated glomerular filtration rate (eGFR) at baseline were predictive of bone loss at the hip and spine, according to Dr. Sophie A. Jamal of the University of Toronto and her colleagues.

“One way to decrease the economic costs, morbidity, and mortality associated with fractures in patients with [chronic kidney disease] is to identify patients at high risk and target treatments to this group,” Dr. Jamal and her colleagues wrote. The investigators analyzed baseline data to calculate eCCr and eGFR in 191 men and 444 women who were aged at least 50 years.

BMD was measured with dual-energy x-ray absorptiometry at the lumbar spine, femoral neck, and total hip.

Participants also had filled out questionnaires to assess risk factors for fractures and use of medications. The study ran from 2000 to 2005.

“The primary predictor of change in BMD during 5 years was eCCr measured at baseline and stratified into quartiles. Our secondary predictor was eGFR, also stratified into quartiles,” the researchers wrote.

The quartiles represented highest to lowest eCCr (from greater than 101.2 mL/min in the first quartile to less than 68.3 mL/min in the fourth) and eGFR (from greater than 86.3 mL/min to less than 68.5 mL/min) (Am. J. Kidney Dis. 2010;55:291-9 [doi:10.1053/j.ajkd.2009.10.049

“A cross-sectional analysis showed that compared with those in the first quartile, those with more impaired kidney function (in the second, third, and fourth quartiles of eCCr) had lower BMD at the lumbar spine, femoral neck, and total hip at year 5,” Dr. Jamal and her coinvestigators wrote.

Over the long term, they added, “these modest decreases result in substantial bone loss.”

Among the study's limitations were its observational design, its small sample size of all-white community dwellers, and, most importantly, the issue of competing mortality.

“To estimate longitudinal change in BMD, participants had to survive to the second measurement. It is possible that participants with the greatest impairment in kidney function had the most rapid bone loss and died before year 5, and as such, were not included in the analysis,” the researchers wrote.

The authors stated they had no financial conflicts to disclose.

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