Type 2 Diabetes Increased Risk of Heart Disease, Stroke, and Death

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Almdal T, Scharling H, Jensen JS, et al.: The independent effect of type 2 diabetes mellitus on ischemic heart disease, stroke, and death: A population-based study of 13,000 men and women with 20 years of follow-up. Arch Intern Med 164:1422-1426, 2004.

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

Studies show that people with type 2 diabetes have a higher risk of cardiovascular diseases (CVD, or disease of the heart and blood vessels) and serious problems such as heart attack or stroke.

Most studies so far have followed specific groups of people. Researchers wanted to look at the risks of CVD in a larger, mixed population of people with type 2 diabetes.

Who was studied?

A total of 13,105 adults: 7,198 women and 5,907 men. All were part of the 20-year Copenhagen City Heart Study. Participants were divided into three groups. One group was made up of people with type 2 diabetes. Another was made up of people with blood glucose levels ranging from 120 to 200 mg/dl. The third group was made up of people with blood glucose levels of 120 mg/dl or lower.

At the start of the study, none of the participants had ever been hospitalized for serious CVD, heart attack or stroke.

How was the study done?

At the start of the study, participants filled out survey questions on cardiovascular risk factors. These included tobacco and alcohol use and physical activity.

Their body mass index (BMI, a measure of weight in relation to height) was calculated. Their blood pressure was taken. Blood samples were taken to measure levels of cholesterol and triglycerides (types of fat in the blood).

The patients were then followed for the next 20 years.

What did the researchers find?

People with type 2 diabetes have a much greater risk of serious problems with CVD. Compared to people without diabetes, the risk of heart attack is 1.5 to 4.5 times greater for women and 1.5 to 2 times greater for men. Also, the risk of stroke is 2 to 6.5 times greater among women with type 2 diabetes and 1.5 to 2 times greater for men.

For women, smoking, high blood pressure, high triglycerides, and heavy alcohol use all increased risk of death. For men, smoking, high blood pressure, heavy alcohol use, and low BMI increased risk of death.

For both men and women, high physical activity and high total cholesterol decreased the risk of death.

What were the limitations of the study?

The percentage of people with diabetes in the study group seems low compared with similar studies. Only 1.4% of women and 3.4% of men had diabetes. This may be because the researchers didn't include all people taking insulin.

What are the implications of the study?

The study shows the importance of controlling risk factors for people with type 2 diabetes. Also, it shows the importance of encouraging exercise.