PITTSBURGH, Dec. 6 -- Symptoms of depressionÐnot high blood sugarÐpredict coronary heart disease (CHD) among people with Type 1 diabetes, according to researchers at the University of Pittsburgh Graduate School of Public Health (GSPH) in a report published in the January 2000 issue of Atherosclerosis.
"We believe this is the first study to show that depressive symptomology is linked to coronary heart disease in Type 1 diabetes," said Trevor J. Orchard, M.D., professor of epidemiology at GSPH and principal investigator on the study. These results also provide further evidence that blood sugar levels fail to strongly predict the likelihood of this complication.
Investigators say they were not surprised to identify increased depressive symptoms as a risk factor, since depression is emerging as a risk factor for cardiovascular disease in the general population. "But the strength of the link was surprising," said Dr. Orchard, who added, "In addition, these results suggest that the high blood sugar association with the development of coronary heart disease among Type 1 diabetics is complex."
The study looked at risk factors for CHD and lower extremity arterial disease (LEAD), both common complications of Type 1 diabetes, and found that these two vascular disorders have different sets of risk factors, although both are thought to be due to the same disease process--atherosclerosis.
"We were particularly surprised to find no relationship between high glycemic levels and CHD, despite the fact that blood sugar and LEAD are closely connected," said Dr. Orchard.
These findings open doors to potential new ways of helping Type 1 diabetics avoid the development of vascular diseases, according to Dr. Orchard. "Knowing the risk factors for CHD and LEAD could help physicians develop specialized prevention and treatment plans," he said, adding that watching for symptoms of depression could be particularly helpful in managing CHD in Type 1 diabetics.
The current analysis used data from the Pittsburgh Epidemiology of Diabetes Complications Study, an ongoing 10-year prospective study of risk factors for complications of childhood-onset Type 1 diabetes. A total of 658 Type 1 diabetic participants (332 men and 326 women) were initially examined during the period 1986 through 1988, and then every two years, for diabetes complications and their risk factors. CHD was defined as the presence of angina, or a history of heart attack or death from CHD. The researchers measured LEAD using a comparison of blood pressures from the leg and arm.
Results showed that factors leading to CHD in Type 1 diabetics include hypertension, depressive symptoms, kidney disease and low levels of HDLc (good) cholesterol. Besides high blood sugar, risk factors for LEAD are smoking and high levels of LDLc (bad) cholesterol. A longer duration of the Type 1 diabetes condition is a factor for both CHD and LEAD, and men tend to develop CHD slightly more often than do women, while women have a slightly higher incidence of LEAD.
"Going into this study, we suspected that traditional risk factors - blood pressure and blood lipids - alone would not explain the high incidence of CHD in Type 1 diabetics," Dr. Orchard said. "We felt there were other important risk factors involved, and now we know that they include symptoms of depression."
Now that a link has been established between CHD and depression, Dr. Orchard said more studies are needed on the relationship between the two. Researchers at the University of Pittsburgh are currently pursuing additional analyses.
While CHD and LEAD often occur with age in the general population, they occur earlier and progress more rapidly among Type 1 diabetics. The reasons for this accelerated atherosclerosis are not entirely known.
Type 1 diabetes is the more severe, insulin-dependent form of the disease, affecting nearly one million people in the United States. Formerly known as "juvenile diabetes," Type 1 diabetes can occur at any time throughout life, but it generally strikes before the age of 35, according to Dr. Orchard. Type 2 diabetes comes on more gradually, usually after the age of 40, and it often affects people who are overweight. While 85 to 90 percent of diabetics are classified as Type 2, Dr. Orchard said evidence shows that about 10 percent of these individuals are really Type 1.
Regardless of whether one has Type 1 or Type 2, inadequately controlled blood sugar levels in diabetes can produce severe damage to small blood vessels, which can result in blindness, kidney disease and peripheral nerve damage.
The University of Pittsburgh study is supported by a grant from the National Institutes of Health. For more information about the GSPH at the University of Pittsburgh, please access http://www.pitt.edu/~gsphhome/. .
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Atherosclerosis