Diabetic Kidney Disease Rates Remain Steady, but Manifestation has Shifted

Analysis of adult diabetics between 1998 and 2014 has found a significant shift in how kidney disease presents itself, a shift that may have implications for both diagnoses and treatment.

Investigators studied 6,251 diabetic patients who participated in the National Health and Nutrition Examination Surveys between 1988 and 2014: 1,431 who participated from 1988-1994, 1,443 from 1999-2004, 1,280 from 2005-2008, and 2,097 from 2009-2014.

They checked all patients for signs of diabetic kidney disease: persistent albuminuria, reduced estimated glomerular filtration rate (eGFR), or both.

The overall prevalence of diabetic kidney disease did not significantly change over time. It was 28.4% in 1988-1994, and it was 26.2% in 2009-2014 (prevalence ratio, adjusting for age, sex and race/nicity, 0.95; 95% CI, 0.86-1.06; p= 0.39 for trend).

However, the way kidney disease presented itself changed significantly from the first study period to the last. The prevalence of albuminuria decreased progressively from 20.8% in 1988-1994 to 15.9% in 2009-2014. The prevalence of reduced eGFR, on the other hand, rose from 9.2% in 1988-1994 to 14.1% in 2009-2014.

There was a similar pattern for severely reduced eGFR (<30 mL/min/1.73 m2). The adjusted prevalence ratio of the 2009-2014 period compared to the 1988-1994 period was 2.86 (95% CI, 1.38-5.91; p=&thinsp;0.004 for trend).

The eGFR trends held true for patients of both sexes and all ages, races and ethnicities. The changes in albuminuria rates, however, were only observed among patients under 65 years old and non-Hispanic whites.

Albuminuria, which indicates elevated levels of protein in the urine, has traditionally been the first detectable sign of damage to a diabetic patient’s kidneys. Reduced eGFR, which indicates declining ability to filter waste products out of the body, traditionally appears only after kidney disease progresses.

The authors of the new study, which appears in the Journal of the American Medical Association, suspect the reduction in albuminuria may stem from improved blood-sugar control, blood-pressure control and/or the hemodynamic effects of renin angiotensin aldosterone system (RAAS) inhibitors.

As for the trend toward reduced eGFR, the cause was less clear. It may be a consequence of increasing disease duration among American diabetics, the study authors wrote, noting that study participants who’d lived the longest with diabetes were the most likely to have reduced eGFR.

The results of the new study may indicate that physicians are missing cases of kidney damage in diabetic patients who have reduced eGFR but not the albuminuria that typically gets tested for. Those study results may also begin a hunt for medications that can halt or reverse reductions in eGFR.

“This ties into what the NIH calls the precision medicine initiative, which is an initiative to look at genetics and biomarkers and other factors to understand what's going on in individuals and to target therapies to individuals,” said the study’s lead author, Ian de Boer, an associate professor of medicine at the University of Washington. “In the kidney medicine space, how that is being applied is we would like to understand more than a person's albuminuria status and GFR. We want to understand a person's underlying biologic processes so we can target therapies to them.”