Definitions of chronic kidney disease need to change, study suggests

More women than men have chronic kidney disease, but more men develop kidney failure

More women than men have chronic kidney disease, but more men develop kidney failure.

In an effort to explain the disparity, researchers in Norway “investigated sex differences in the loss of kidney function and whether any sex disparities could be explained by comorbidity or (chronic kidney disease) risk factors,” the scientists wrote in their study, published in the Journal of the American Society of Nephrology.

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In the Renal Iohexol Clearance Survey in northern Europe, the researchers recruited 1837 people who were representative of the general population. Participants were tested to find their mean glomerular filtration rates — or GFR — at baseline. GFR is how much blood your kidneys filter each minute.

Over the course of 11 years of following up on the participants, researchers found men had a 25% steeper mean GFR decline than women, reported Toralf Melsom, MD, PhD, of the University Hospital of North Norway in Tromsø, and colleagues.

“This is the first study that repeats accurate measurements of kidney function in relatively healthy women and men during aging,” Melsom said in a statement, as reported by MedPage Today. “By doing so we provide important knowledge regarding age-related loss of kidney function and sex disparities in the prevalence of chronic kidney disease (CKD). The study may in part explain why more women are diagnosed with early CKD and more men develop severe CKD and kidney failure during aging.”

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To determine the kidney filtration rate, researchers injected participants with the contrast media iohexol, a kidney filtration marker, then took blood samples a few hours later to see check the filtration.

“This method has been regarded as too complicated to use in population-based studies; however during 11 years of follow-up, we performed more than 4,000 kidney function measurements in 1,837 people,” Melsom said in the statement.

According to the scientists, the findings could support age- and sex-specific cutoff values for defining CKD. For example, they wrote, a healthy 70-year-old woman with a GFR of 59 mL/min/1.73 m² and no albuminuria is labeled as having chronic kidney disease stage 3a, “even though her GFR is within the 95% age-and sex-specific reference range in European populations.”

“A CKD diagnosis may cause anxiety and referral to a specialist health care center, but according to our study her risk of accelerated GFR loss is low, and the risk of end stage kidney disease has been found to be minimal,” the researchers wrote.

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On the other hand, the researchers wrote, a man under age 50 with a GFR of 65 mL/min/1.73 m² doesn’t meet the criteria for chronic kidney disease, even though his GFR is clearly abnormal “and his lifetime risk of progression to CKD stages 4 and 5 may be significant.”

“Studies on measured GFR that include sex-specific morbidity or mortality endpoints are needed to decide whether the CKD definition should be adjusted for age and sex,” they wrote.

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