Chronic kidney disease (CKD) is more likely to develop in women compared with men, but men are more likely to progress to kidney failure requiring renal replacement therapy. Now new research sheds light on this apparent contradiction by revealing that age-related kidney function decline occurs more rapidly in healthy men vs women.
In the Renal Iohexol Clearance Survey (RENIS), investigators assessed glomerular filtration rate (GFR) over time in 1837 Northern European adults (53% women) aged 50-62 years. Individuals were healthy at baseline and free of diabetes, CKD, and cardiovascular disease, including a subset who were also free of hypertension, obesity, albuminuria, cancer, and smoking history. For accuracy, the team measured GFR by plasma iohexol clearance over approximately a decade rather than relying solely on estimated GFR using serum creatinine or cystatin.
At baseline, the mean measured GFR was significantly higher among men than women: 98.0 vs 90.0 mL/min/1.73 m2. Men had a 25% steeper rate of annual decline in mean measured GFR than women, however: 1.20 vs 0.96 mL/min/1.73 m2 per year.
“Although the relationship between age and GFR was very close to linear in women, it was curvilinear in men, with steeper GFR slopes at older ages,” Toralf Melsom, MD, of the University Hospital of North Norway in Tromsø, and colleagues reported in the Journal of the American Society of Nephrology.
Rates of kidney function decline in men vs women were more pronounced at older ages. Health status did not explain these differences.
According to the investigators, the findings support age- and sex-specific cutoff values for defining CKD. For example, a 70-year-old healthy woman with a GFR of 59 mL/min/1.73 m2 and no albuminuria is labeled as having CKD stage 3a, but she is well within the normal reference range and has a low risk of kidney failure. Conversely, a man younger than 50 years who has an abnormal GFR of 65 mL/min/1.73 m2 does not meet formal criteria for CKD but carries a significant risk of progression.