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Diabetes Study Partially Halted Due to Cardiac Risk

February 7, 2008 at 6:25 PM EDT
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A new study on Type 2 diabetes was partially halted after research showed lowering blood sugar levels for some high-risk patients increased their chances of dying from a heart attack. The head of the American Diabetes Association details the surprising findings.

RAY SUAREZ: Researchers have long believed that lowering blood sugar in diabetes patients would reduce the risk of dying from heart disease, but that theory was thrown into question yesterday when the National Institutes of Health halted part of a study of more than 10,000 patients with Type 2 diabetes.

The reason: Researchers discovered that aggressively lowering blood sugar levels actually increased their risk of death.

Here to tell us more is Dr. John Buse, vice president of the study’s steering committee and the president of medicine and science at the American Diabetes Association.

Doctor, what question was this clinical trial designed to answer?

DR. JOHN BUSE, American Diabetes Association: Well, as you mentioned, for a long time we’ve thought that lowering blood sugar lowers the risk of complications. And we wanted to specifically look at whether taking blood sugar from a moderate level down to a very low level would reduce complications further than what we already knew.

RAY SUAREZ: And what was the health status of the 10,000 or so people in the study?

DR. JOHN BUSE: Well, they were middle-aged and older. Most of them had had a heart attack in the past or some known vascular disease, but at minimum they had to be middle-aged and have multiple risk factors for cardiovascular disease.

RAY SUAREZ: And remind us again, what is diabetes? What’s actually happening inside the body that’s hurting you?

DR. JOHN BUSE: Diabetes is a disease that’s defined by blood sugar, but 75 percent of people with diabetes eventually die of heart attack or strokes, so it’s really very intimately related to cardiovascular disease.

And the notion is that high levels of blood sugar and the related problems with cholesterol and blood pressure just lead to accelerated atherosclerosis, as well as other complications.

Complications from very low sugar

RAY SUAREZ: So when these patients embark on an aggressive course of lowering blood sugar, what happened to them?

DR. JOHN BUSE: Well, this was a very aggressive program. Very few patients in the United States are treated in this way. Many of the patients had to take multiple injections of insulin a day, monitor their blood sugar very frequently, taken an assortment of pills for blood pressure, cholesterol, diabetes.

They had frequent telephone contact with the study staff, at least every two to four weeks, lots of adjustments of their therapy over time. And we tried to get their blood sugar levels down to normal.

What happened in the end was the data safety and monitoring board noticed that about three patients per 1,000 patients per year more in the intensive group died during the approximately four years of follow-up than in the standard less intensively treated group.

RAY SUAREZ: Well, just a moment ago you explained why it is that high blood sugar, abnormally high blood sugar, was hurting the body and what the risks were. Do we know yet what happened, why more people died when your trials worked so hard to bring their blood sugar down into a normal range?

DR. JOHN BUSE: To be honest, we don't really know. We know a number of things that it doesn't seem to be, as far as what the problem was.

It doesn't seem to be the particular drugs that we used or the particular combinations of drugs that we used. It doesn't seem to be hypoglycemia or low blood sugar. It doesn't seem to be weight gain, which is often a complication of diabetes therapy.

But to be honest, we can't be very definitive about any of these things. But what we do still know is that moderate levels of blood sugar are associated with good outcomes in diabetes. And now we have this concern that going beyond that to very low, normal levels of blood sugar may be associated with a problem in high-risk people.

Altering the study

RAY SUAREZ: Did you stop the tests for all the patients involved in this part, even people who outwardly had their health improved by lowering their blood sugar?

DR. JOHN BUSE: So we actually didn't stop the test. What we've done so far is we've taken the patients who were in the intensive group, where the death rate was a bit higher, and moved them to the standard group.

And, in fact, one of the other very interesting things that we discovered through this process is that the overall rate of death was lower than we expected. It's about half to a third of what we believe to be the background rate of death in patients with diabetes, this degree of diabetes.

So these patients as a whole did very, very well. It's just that there seemed to be a few extra deaths in the intensively treated group.

Taking health precautions

RAY SUAREZ: Well, if you're among the many Americans who may be on the verge of developing Type 2 diabetes or if you have persistently high blood sugar or are, in fact, diabetic, what's the takeaway message from this? What are you telling people they should be doing?

DR. JOHN BUSE: Well, I think takeaway message is, first of all, it's very important if you have diabetes to control your blood pressure and your cholesterol. There's no new message there.

If you're middle-aged and older and you have complications with your diabetes, particularly a prior history of heart attack or stroke, moderate levels of blood sugar seem to be very safe.

So the test that we use to measure average blood sugar is called the A1c, so an A1c of around seven.

In general, for most other people, younger patients, going to lower levels seems appropriate. So, in general, the recommendation is still an A1c of less than seven.

RAY SUAREZ: Dr. Buse, thanks a lot for joining us.

DR. JOHN BUSE: It's a pleasure.