The scientists also found that people suffering from type 2 diabetes who used insulin to get blood sugar levels down to near normal were 50 percent more likely to die during the study period as those who used a combination of oral drugs, such as metformin and sulphonylurea.

But in a large study published in The Lancet medical journal, the researchers from Cardiff University said this may have been because type 2 diabetics who need insulin tend to be older and sicker to start with.

The findings suggest keeping diabetics on oral drugs that increase the body's sensitivity to insulin, combined with diet and exercise, may be the safest way of controlling blood sugar in type 2 diabetics, and doctors should strive to keep their patients on this treatment for as long as possible, they said.

This study will raise a few eyebrows, said Craig Currie, who led the study by a team from Cardiff's medical school.

Conventionally, doctors have always been told to drive down (blood sugar levels) as low as possible. It will come as a major surprise to many doctors that taking people down too far appears to be quite risky, he said in a telephone interview.

Currie said the findings on insulin should not prompt urgent action, but patients should arrange to see their doctor sometime over the next few weeks to discuss it with them.

The study is the latest of several investigating whether using aggressive drug treatments to achieve near normal blood sugar levels can help prevent some of the most serious risks of diabetes, such as heart attacks and strokes.

A U.S. government-sponsored trial called ACCORD was stopped in February 2008 because there were 20 percent more deaths among diabetics with heart problems who got intensive treatment compared to those who were treated more conservatively.

Type 2 diabetes -- often called adult-onset diabetes -- is a common disease that interferes with the body's ability to properly use sugar and insulin, a substance produced by the pancreas which normally lowers blood sugar after eating.

Diabetes is reaching epidemic levels, with an estimated 180 million people suffering from it around the world.

Overweight people have an increased risk of developing it, and cases are predicted to rise swiftly in coming decades as obesity rates also increase.

In this study, scientists analyzed links between death rates and blood sugar levels in almost 48,000 patients who were over 50 and being treated for type 2 diabetes. The data were taken from the UK General Practice Research Database from November 1986 to November 2008.

They found that both patients with the highest blood sugar levels and those with the lowest levels had increased risk of death -- 79 percent and 52 percent respectively. The lowest risk of death was in those with blood sugar levels of 7.5 percent.

Death risk in people given insulin-based treatment was 49 percent higher than those give oral medicines, they said. They also pointed out a possible link between use of insulin and cancer progression that had been reported in a previous study.

(Additional reporting by Julie Steenhuysen in Chicago, editing by Michael Roddy)

Medicine