THURSDAY, Jan. 24, 2013 (HealthDay News) -- For people with type 2 diabetes, the key to living a long and healthy life may lie in avoiding kidney disease, now that new research finds the combination is particularly lethal.
The study found that 10-year mortality rates for people with both type 2 diabetes and kidney disease is more than 31 percent. But for people with only type 2 diabetes, the death rate after a decade was 12 percent. For those with neither condition, the 10-year death rate was about 8 percent.
"We've all been trained to think of type 2 diabetes as a bad thing, but it's particularly bad when you get kidney disease, too," said study author Dr. Maryam Afkarian, a kidney specialist and an assistant professor of medicine at the University of Washington in Seattle.
On the other hand, "We found that type 2 diabetes may not affect mortality as much if you don't get kidney disease," she said.
Results of the study are published in the February issue of the Journal of the American Society of Nephrology.
People with type 2 diabetes do not produce or properly use insulin, a hormone needed to convert food into energy. In the United States, about 26 million people have diabetes, and the number is growing. Type 2 diabetes has long been associated with an increased risk of death, especially from cardiovascular disease. And kidney disease is common in people with type 2 diabetes.
To better understand how the two diseases behave together, the researchers reviewed 10 years of data from the U.S. National Health and Nutrition Examination Survey, involving more than 15,000 people. About 42 percent of people with type 2 diabetes had kidney disease, they found.
When the researchers controlled the data to account for factors such as age, sex and body-mass index -- a calculation based on height and weight -- as well as duration of diabetes, the rates of death remained high for people with kidney disease and diabetes, at about 23 percent. The 10-year mortality for those with only type 2 diabetes was 9 percent when the data was adjusted for such factors, while the rate of death for people without diabetes or kidney disease was about 3 percent.
"As we expected, those with diabetes and kidney disease had a lot higher risk of mortality," said Afkarian.
"Clearly, we're not at the point of stopping type 2 diabetes," she said, "so the next question becomes, 'What happens if we can keep the kidneys healthy?'"
She said prevention efforts should focus on people who have diabetes but not kidney disease. "Try to control your risk factors to prevent kidney disease," she suggested. And, the biggest risk factor is uncontrolled blood sugar.
However, there also is a genetic component to developing kidney disease, she said. So, if you have those genes, you may develop kidney disease even if your blood sugar is well-controlled. But for most people with type 2 diabetes, controlling blood sugar levels can help prevent kidney disease, or at least slow its progression, she said.
Dr. Joel Zonszein, director of the Clinical Diabetes Center at Montefiore Medical Center in New York City, approved of the analysis. "It shows that once someone is sick, it's a bad marker," he said.
"We always have to emphasize much more on prevention. There's a nice correlation between A1C (a long-term measure of blood sugar control) and kidney disease. And people without high blood pressure tend to do better," he noted.
The problem, he said, is that it's often "a long time before people are diagnosed with type 2 diabetes, and when they are diagnosed, they're often undertreated, which leads to uncontrolled diabetes."
Zonszein said many people with type 2 diabetes who should be taking cholesterol and blood-pressure lowering medications aren't on them. Afkarian said people who have both type 2 diabetes and kidney disease should be monitored more closely by their physicians.
It's important to remember that it's much easier to prevent kidney disease than to stop it once it's begun, Afkarian said.
"There's a long time to intervene before kidney disease sets in," she said. "It can make all the difference in the world."
Learn more about diabetes and kidney disease from the American Diabetes Association.