Diabetes has long been recognized by clinicians as a risk factor for heart disease. Now a study shows the association works both ways: MIs pose a significant risk for developing diabetes or impaired fasting glucose (IFG), a prediabetic condition.

In the study, an American-Italian team analyzed data involving 8,291 patients collected during an earlier randomized Italian trial. All the participants had had an MI within the previous three months, and none had diabetes. But during 3.5 years of follow-up, 998 (12%) developed the disease, defined as ≥7 mmol/L blood glucose.

Compared with the general population, these patients were up to 4.5 times more likely to develop new-onset diabetes (3.7% vs. 0.8%-1.6%) and greater than 15 times more likely to develop IFG (27.5% vs. 1.5%).

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Of the 7,533 patients whose baseline fasting glucose level was ≤6.1 mmol, 33% developed either diabetes or IFG. The proportion doubled to two thirds, when a normal blood glucose level of 5.6 mmol/L was used for analysis.

“These findings indicate that just as diabetes can be considered a coronary heart disease risk-equivalent, acute MI should potentially be considered a prediabetes risk-equivalent,” the researchers conclude (Lancet. 2007;370:667-675).

“Patients with both coronary heart disease and diabetes had significantly worse outcomes than people with only one of these conditions,” they add. These included greater likelihood of dying. Compared with patients whose fasting glucose was normal, patients with levels between 5.6 and 6.05 mmol/L faced a 10% higher risk of death. That risk became 15% higher in patients whose blood glucose was between 6.1 and 7 mmol/L and soared to 44% higher with the onset of diabetes.

However, the study also found that smoking cessation, healthy weight, and eating a more Mediterranean-style diet rich in fruits, vegetables, poultry, fish, and nuts were factors that substantially lowered the chances of developing diabetes or IFG.

“This has important implications for counseling patients soon after they have an MI,” the researchers note. “It’s an opportune time to institute lifestyle changes in patients motivated by a life-changing event.”