High Homocysteine Levels Increase Risk for Heart Attacks in People with Type 2 Diabetes Mellitus

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The summary below is from the full report titled "Elevated Plasma Homocysteine Level Is an Independent Predictor of Coronary Heart Disease Events in Patients with Type 2 Diabetes Mellitus." It is in the 20 January 2004 issue of Annals of Internal Medicine (volume 140, pages 94-100). The authors are M. Soinio, J. Marniemi, M. Laakso, S. Lehto, and T. Rönnemaa.

What is the problem and what is known about it so far?

Heart attacks remain leading causes of death and disability in most western countries. Smoking, high-fat diet, high cholesterol level, high blood pressure, diabetes, and kidney disease increase a person's risk for coronary heart disease and heart attacks. Recently, researchers identified several additional risk factors for heart disease. One of them is homocysteine level. Homocysteine is an amino acid that may be increased when intake of vitamins, such as folic acid, is low. Most studies that show that high homocysteine levels increase risk for heart attacks were in patients who already had coronary artery disease and did not have diabetes. Few studies address whether homocysteine level increases risks for heart attacks in people with diabetes mellitus.

Why did the researchers do this particular study?

To see whether high levels of homocysteine increase risks for heart attacks in adults with type 2 diabetes.

Who was studied?

830 Finnish men and women, 45 to 64 years of age, with type 2 diabetes.

How was the study done?

Researchers identified adults with diabetes from a Finnish national drug registry. Between 1982 and 1984, they measured each person's blood pressure and weight. They asked about smoking habits, alcohol intake, physical activity, medications, and chest pain. They took blood tests to measure levels of homocysteine, glucose, cholesterol and other lipids, and creatinine (a measure of kidney function). They also used blood tests (C-peptide values) to see which patients had type 1 and type 2 diabetes. Seven years later, the researchers reviewed death certificates and medical records to see whether anyone had died of or had been hospitalized with a heart attack. They then examined whether the heart attacks occurred more often in persons who had high homocysteine levels 7 years previously.

What did the researchers find?

High levels of homocysteine (plasma homocysteine levels 15 µmol/L) were associated with increased risk for fatal and nonfatal heart attacks, even after accounting for several other risk factors. High homocysteine levels also increased risks for death from heart attack.

What were the limitations of the study?

Researchers used a drug registry to identify study participants. Healthier people with early and less severe type 2 diabetes might not be listed in the registry. The study did not measure folate intake or changes in risk factors over time. It cannot tell us whether lowering homocysteine level with higher folate intake would reduce coronary artery disease.

What are the implications of the study?

Homocysteine is an independent risk factor for heart attacks in adults with type 2 diabetes.