Tight Blood Sugar Control in Older Diabetics May Not Reduce Heart Risk
But intensive control does improve other conditions, including eye and kidney health, study finds
TUESDAY, June 29 , 2010 (HealthDay News) -- Intensive control of blood glucose levels does not reduce the odds of cardiovascular disease for those with long-term type 2 diabetes who are at risk of heart problems, as researchers have known. But it may have some other benefits, a new analysis suggests.
Strict control of blood sugar in a certain group of patients may slow progression of eye disease and help kidney and peripheral nerve health, the researchers found.
The new study is the latest analysis from the ACCORD (Action to Control Cardiovascular Risk in Diabetes) trial.
The study results, like the previous research, apply only to a certain group of people with diabetes, said study lead author Dr. Faramarz Ismail-Beigi, professor of medicine at Case Western Reserve University and University Hospitals of Cleveland.
"The trial fundamentally is on older adults, average age 60, who had diabetes 10 years on average," he said. "All are type 2." Because they have had the disease for 10 years, typically the disease has progressed, he said. The 10,251 participants had either a history of heart disease or two or more risk factors for it.
The study compared intense blood sugar control -- A1C values of less than 6 percent -- with standard, 7 to 7.9 percent, control. A1C levels reflect blood sugar levels over the preceding three months. Under 6 percent is viewed as normal; diabetics are often advised to keep it at around 7.
The study results, published online June 29 in The Lancet, were to be presented Tuesday at the American Diabetes Association annual meeting, in Orlando, Fla.
Study participants were assigned to either intensive glucose-control therapy or standard therapy. When it was found that those in the intensive group had an increase in deaths, the study was stopped in February 2008, and all participants were switched to the standard group for the remainder of the five-year follow-up, which ended in June 2009.
In this new analysis, the researchers looked at kidney, eye and nerve problems. The intensive therapy did not reduce the risk of problems such as advanced kidney or eye complications. But it did delay the onset of albuminuria, protein in the urine, which is associated with renal failure, and some eye complications and nerve problems.
But those on tight control also gained more weight and were at risk for very low blood sugar, the study found.
The researchers concluded that: "The observed benefits associated with intense glycaemia management should be weighed against higher total and cardiovascular-related mortality, weight gain, and severe hypoglycaemia in patients at high risk of cardiovascular disease."
"A target of 6 percent or less with present strategies seems imprudent," the researchers wrote.
In a commentary accompanying the study in The Lancet, Dr. Ronald Klein of the University of Wisconsin School of Medicine and Public Health, Madison, noted the three-fold increase in severely low blood sugar found in those on intensive therapy. Technological improvements are needed, he said, to normalize blood sugar without causing it to drop dangerously low.
It's not surprising that no benefits were found for all complications, Klein said. "The study didn't really go long enough," he said, to observe the protective effect of intensive therapy on some complications.
Even so, he added, it's still crucial to control blood sugar -- perhaps just not as intensively as researchers previously thought necessary.
Other researchers in a subgroup of the ACCORD study reported online June 29 in the New England Journal of Medicine that tight glucose control helped reduce the progression of retinopathy, a common complication of diabetes that can cause blindness.
Looking at 2,856 study participants, the subgroup researchers found that the rates of progression of diabetic retinopathy were 7.3 percent with intensive therapy but 10.4 percent with standard therapy. Retinopathy was also less likely to progress in those who got intensive cholesterol-lowering treatment, but intensive blood pressure control had little effect on the eye disease, the researchers said.
In an editorial accompanying the study in the journal, Dr. Barbara Klein, also of the University of Wisconsin, Madison, said the subgroup study adds valuable information about the effect of blood sugar on retinopathy and points to the need for further study of the value of cholesterol-lowering drugs.
To learn more about eye complications of diabetes, visit the American Diabetes Association.