Lowering blood sugar levels could reduce the risk of
coronary heart disease in both diabetics and nondiabetics,
according to researchers at the Johns Hopkins
Bloomberg School of Public
Health and other institutions.
The researchers found that Hemoglobin A1c — a
measure of long-term blood glucose level — predicts
heart disease risk in both diabetics and nondiabetics. An
elevated blood glucose level is the defining feature of
diabetes, but until now it was unclear whether elevated
glucose levels contributed independently to increasing
heart disease risk. The study is published in the Sept. 12
issue of Archives of Internal Medicine.
"In persons with diabetes, we know that traditional
cardiovascular risk factors, such as hypertension and high
cholesterol, should be treated aggressively. Our results
also suggest that improving blood-glucose control may
further reduce heart disease risk," Elizabeth Selvin, lead
author of the study and a postdoctoral fellow in the
Bloomberg School's
Department of Epidemiology, said. "For nondiabetics,
lifestyle modifications such as increased physical
activity, weight loss and eating a healthful, low-glycemic
index diet rich in fiber, fruit and vegetables, may not
only help prevent diabetes but also reduce the risk of
heart disease," she said.
The researchers used data from the Atherosclerosis
Risk in Communities Study, a community-based cohort of
almost 16,000 people from North Carolina, Mississippi,
Maryland and Minnesota. Hemoglobin A1c, or HbA1c, levels
were taken from ARIC study participants during clinical
examinations from 1990 to 1992. ARIC researchers tracked
study participants for 10 to 12 years to acquire coronary
heart disease events, hospitalizations and deaths.
In participants with diabetes, the researchers found a
graded association between HbA1c and increasing coronary
heart disease risk. Each 1 percentage point increase in
HbA1c level was associated with a 14 percent increase in
heart disease risk. According to the study authors, the
current target for "good" glycemic control established by
the American Diabetes Association is an HbA1c value less
than 7 percent. However, the researchers' analyses suggest
that heart disease risk begins to increase at values even
below 7 percent.
They found that those study participants without
diabetes but who had "high normal" HbA1c levels
(approximately 5 percent to 6 percent) were at an increased
heart disease risk, even after accounting for other factors
such as age, cholesterol level, blood pressure, body mass
index and smoking. Nondiabetic persons with HbA1c levels of
6 percent or higher had almost a twofold greater heart
disease risk compared to persons with an HbA1c level below
4.6 percent.
"There are large, ongoing clinical trials which should
definitively answer the question of the effectiveness of
blood glucose-lowering medications in decreasing
cardiovascular risk in persons with type-2 diabetes. But
our results suggest we should also be concerned about
elevated blood sugar levels in nondiabetics as well. An
important next step is to investigate strategies for
lowering HbA1c in persons without diabetes," Selvin
said.
Co-authors of the study are Elizabeth Selvin, Josef
Coresh, Sherita H. Golden, Frederick L. Brancati, Aaron R.
Folsom and Michael W. Steffes.
They were supported in part by grants from the
National Heart, Lung and Blood Institute.
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