Posted: Jun 21, 2011 11:43 PM
June 21, 2011 -- The number of Americans with diabetic kidney disease is rising, a new study shows.
About 40% of people with diabetes will develop kidney disease, a serious and costly complication that greatly increases the risk of other health problems, including cardiovascular disease.
Diabetic kidney disease is also the leading cause of end-stage renal disease, which requires treatment with regular dialysis or a kidney transplant.
Using data from government health surveys, researchers at the University of Washington, Seattle, found a 34% increase in cases of diabetic kidney disease from 1988 to 2008.
The percentage of diabetic people identified by the study who developed kidney disease did not appear to change during those years, holding steady at about 35%.
But because more people are developing diabetes, the numbers with kidney disease are also going up, the study shows.
That's discouraging, experts say, especially since management of diabetes has markedly improved over the last two decades.
More diabetic people now take medications to lower their blood glucose and cholesterol, and more are taking medications that lower blood pressure called renin-angiotensin-aldosterone system (RAAS) inhibitors, which are thought to protect the kidneys.
And at least in some respects, the medications seem to be making a difference. The study found that average blood glucose, blood pressure, and LDL"bad" cholesterol numbers have all gone down in diabetic people.
But kidney disease in diabetic people hasn't budged.
"I was hoping that would we see, among people with diabetes, a reduction in diabetic kidney disease and was surprised that that was not the case," says study researcher Ian H. de Boer, MD, assistant professor of medicine in the Kidney Research Institute at the University of Washington.
"We need to find ways to do more," de Boer says, "either by preventing diabetes itself, or by preventing diabetic kidney disease through new routes."
Why better treatments haven't seemed to put a dent in diabetic kidney disease has experts scratching their heads.
It may be that better treatments are helping to extend the health of the kidneys, delaying kidney disease until later in life, says Trevor J. Orchard, MBBCh, professor of epidemiology, pediatrics, and medicine at the University of Pittsburgh's Graduate School of Public Health.
Doctors used to think that if a person had lived with diabetes for more than 25 years and not developed kidney disease, they were unlikely to ever get it.
"Now, what we're seeing is the incidence is being pushed back 20 or 30 years and starting to rise then, and I think that's purely a result of the better blood pressure control, the better glycemic control, and the ACE inhibition," says Orchard, who was not involved in the study.
For the study, researchers looked at two common measures of kidney disease: albuminuria, or the presence of protein in the urine, and glomerular filtration rate (GFR), which is gauges how quickly the kidneys are able to clean waste out of the blood.
"They're each a sign of kidney disease. They probably reflect different types of kidney damage," de Boer says.
Over the two decades covered in this study, de Boer says they saw a shift toward less protein in the urine, but worse GFR, or kidney function.
He says it could be that current diabetes treatments may be lowering protein in the urine while failing to help or perhaps worsening GFR.
"They're each important manifestations of kidney disease. Each of those signs is bad. They're both associated with increased risks of cardiovascular disease and increased mortality rates," he says. "Having either one is bad, and both are worse."
"This paper shows it's actually the low GFR side of kidney disease that is most troublesome and increasing," de Boer says.
The study is published in the Journal of the American Medical Association.