Modest Kidney Function Loss Speeds Bone Mineral Density Decline

NEW YORK—Even slight kidney impairment can speed up the loss of bone mineral density (BMD) among older people, putting them at risk of potentially disabling fractures, according to a study in the February issue of the American Journal of Kidney Diseases.

“Our findings highlight the importance of estimating kidney function when evaluating patients for fracture risk,” said Sophie A. Jamal, MD, PhD, of the University of Toronto, and her colleagues.

Most people who have chronic kidney disease (CKD), or who are at risk for this condition, don’t know it, according to Dr. Kerry Willis, senior vice president for scientific activities at the National Kidney Foundation. “The new findings show the potential impact of early identification of kidney disease in preventing complications that can cause disability and premature death,” Willis said.

When a person’s kidney function is completely lost—a condition known as end-stage renal disease—he or she is at much greater risk of sustaining a hip fracture, Jamal and her colleagues explained in their report.

To better understand the relationship between more modest kidney impairment and bone loss, the researchers followed 191 men and 444 women age 50 and older for five years. They used two different techniques—estimated creatinine clearance and estimated glomerular filtration rate—to gauge patients’ kidney function at the beginning of the study. The first test measures how quickly the kidneys clear creatinine (a waste product), from the blood, and the second gauges the speed at which fluid flows through the kidney. Study participants also had their BMD measured at the beginning of the study and five years later.

Jamal and her team found that the people with impaired kidney function lost BMD faster than those whose kidneys were working normally.

For example, the study participants with the worst kidney function showed a 9.3 percent greater decrease in their lower spine BMD over a five-year period compared to those with normally functioning kidneys.

The results were basically the same with either kidney function measure.

“Not only is this a substantial loss, but equally concerning is that the bone loss occurs with even modest impairment of kidney function,” said Jamal and her colleagues.