Diabetes is dangerous even before the disease becomes full-blown, boosting the risk of death from heart disease in its earliest form, Australian researchers said on Monday.

Before most people develop type 2 diabetes, they have trouble metabolizing sugar, a problem known as pre-diabetes that affects 56 million people in the United States.

Elizabeth Barr of the International Diabetes Institute in Melbourne, Australia, said that a large study found people with pre-diabetes had more than double the risk of death from heart disease after five years.

Type 2 diabetes is linked with obesity, poor diet and lack of exercise and is becoming a growing problem in many parts of the world. It can lead to blindness, limb loss, heart disease and early death.

Barr and colleagues studied 10,429 Australians age 25 or older for about five years. Patients were considered pre-diabetic if they had abnormal blood glucose levels after fasting.

These patients have a 2.5 times higher risk of death from heart problems than those who metabolized glucose normally, said the researchers, whose work was published in the journal Circulation.

“This study confirms the clinical importance of pre-diabetes, and suggests the need to target glucose abnormalities with lifestyle interventions,” Barr said in a statement.

Studies have shown that people with pre-diabetes can prevent type-2 diabetes through dietary changes and increased physical activity.

The pre-diabetes finding follows another large study that suggests people with type 2 diabetes have a far higher risk of stroke even within the first five years of diagnosis.

In that study, researchers at the University of Alberta in Canada, evaluated 12,272 people with type 2 diabetes. All had been recently diagnosed with diabetes and had a mean age of 64 years.

After five years, they compared the rate of stroke among the diabetics in the study with the general population and found the type-2 diabetics had double the risk of having a stroke.

The study, published recently in the American Heart Association’s journal Stroke, was among the first to look at the stroke risk of newly diagnosed diabetics.

Most studies have looked at stroke rates among diabetics within 10 years of diagnosis.

“We hope our findings will help dispel the notion that the risk of stroke occurs only in the long term,” Dr. Thomas Jeerakathil, an assistant professor of neurology who led the study at the university, said in a statement.