Pre-Diabetics Face High Heart Attack Risk Now*

New research shows that cardiovascular risks can increase even before patients develop diabetes.

People with diabetes have a higher than average risk of developing cardiovascular disease. Researchers led by Dr. Frank B. Hu of the Harvard School of Public Health in Boston, Massachusetts found that women who later developed type 2 diabetes had a risk of heart attack almost 4 times higher than women who never developed diabetes. Once women were diagnosed with diabetes, the risk increased to 4.5 times that of non-diabetics.

The researchers uncovered the same trend in risk of stroke. Undiagnosed diabetics had more than twice the risk of stroke as those who were never diagnosed with the disease.

So even before people develop diabetes, their heart disease risk is already elevated.

Consequently, "for pre-clinical diabetes, it's very important to manage your cardiovascular risk factors," he added. These include being overweight, sedentary and having high blood pressure, as well as having high levels of certain fats in the blood. All of these risk factors can be managed with diet, exercise and medications if necessary.

These findings are based on a 20-year follow-up of 117,629 female nurses. When the women first entered the study in 1976, only 1,508 had type 2 diabetes. During the study, the researchers observed how many women suffered heart disease or stroke, and who developed type 2 diabetes.

Over the 20-year period, an additional 5,894 women were diagnosed with type 2 diabetes. The women also had 1,556 heart attacks and 1,405 strokes. Eight hundred and fifteen women died of heart disease, and another 300 died from stroke, Hu and his team write in the July issue of Diabetes Care.

Hu explained that researchers have long suspected that the risk of cardiovascular disease may climb years before a person is diagnosed with diabetes. According to the "common soil" hypothesis, both conditions stem from similar risk factors, such as obesity.

However, during the study, when Hu and his colleagues eliminated the influence of risk factors for both conditions, they found that those later diagnosed with type 2 diabetes still had a higher-than-average chance of having heart attack or stroke before their diagnosis. As such, he suggested that some soon-to-be diabetics may have insuliun resistance--a pre-diabetic condition in which the body fails to efficiently respond to insulin, and which can also increase the risk of developing cardiovascular disease.

He recommended that people with a family history of diabetes who are obese check in regularly with their doctors to see if they have developed insulin resistance. And when people are diagnosed with diabetes, Hu suggested they try to temper their risk of cardiovascular disease through diet, exercise and by controlling blood pressure if it is too high.

In another study using the same group of patients and published in the same issue of Diabetes Care, Hu and another research team, led by Dr. Eunyoung Cho of Harvard Medical School, found that the more overweight diabetic women were, the higher their risk of developing cardiovascular disease.

Interestingly, women who gained weight before being diagnosed with diabetes--even starting as young as 18 years old--also had a higher than average risk of cardiovascular disease.  However, weight changes that occurred after a diagnosis of diabetes appeared to have no significant impact on the chance of developing cardiovascular disease.

It is very difficult to study the impact of weight changes after being diagnosed with diabetes, Hu explained, so these results should not be interpreted as a green light for diabetics to gain weight. Rather, the findings provide further evidence that body changes that occur before a diagnosis of diabetes can have a significant impact on future health.

"Weight gain in adulthood, even prior to a diagnosis of diabetes, can substantially increase the risk of cardiovascular disease," Hu noted. SOURCE: Diabetes Care 2002;25:1129-1134, 1142-1148.