Lowering blood sugar levels could reduce the risk of coronaryheart disease in both diabetics and non-diabetics, according toresearchers at the Johns Hopkins Bloomberg School of Public Health andother institutions. The researchers found that Hemoglobin A1c (HbA1c)—ameasure of long-term blood glucose level—predicts heart disease risk inboth diabetics and non-diabetics. An elevated blood glucose level isthe defining feature of diabetes, but until now it was unclear whetherelevated glucose levels contributed independently to increasingheart-disease risk. The study is published in the September 12, 2005,issue of Archives of Internal Medicine.
“In persons withdiabetes, we know that traditional cardiovascular risk factors, such ashypertension and high cholesterol, should be treated aggressively. Ourresults also suggest that improving blood-glucose control may furtherreduce heart disease risk,” said Elizabeth Selvin, PhD, MPH, leadauthor of the study and a postdoctoral fellow in the Bloomberg Schoolof Public Health’s Department of Epidemiology. “For non-diabetics,lifestyle modifications, such as increased physical activity, weightloss and eating a healthful, low-glycemic, index diet rich in fiber,fruit and vegetables, may not only help prevent diabetes, but alsoreduce the risk of heart disease,” she said.
The researchers useddata from the Atherosclerosis Risk in Communities Study (ARIC), acommunity-based cohort of almost 16,000 people from four states—NorthCarolina, Mississippi, Maryland and Minnesota. HbA1c levels were takenfrom ARIC study participants during clinical examinations in 1990-1992.ARIC researchers tracked study participants for 10-12 years to acquirecoronary heart disease events, hospitalizations and deaths.
Inparticipants with diabetes, the researchers found a graded associationbetween HbA1c and increasing coronary heart disease risk. Each1-percentage-point increase in HbA1c level was associated with a 14percent increase in heart disease risk. According to the study authors,the current target for “good” glycemic control established by theAmerican Diabetes Association is an HbA1c value less than 7 percent.However, the researchers’ analyses suggest that heart disease riskbegins to increase at values even below 7 percent.
They foundthat those study participants without diabetes but who had “highnormal” HbA1c levels (approximately 5 percent to 6 percent) were at anincreased heart disease risk, even after accounting for other factorssuch as age, cholesterol level, blood pressure, body mass index andsmoking. Non-diabetic persons with HbA1c levels of 6 percent or higherhad almost a two-fold greater heart disease risk compared to personswith an HbA1c level below 4.6 percent.
“There are large, on-goingclinical trials which should definitively answer the question of theeffectiveness of blood glucose-lowering medications in decreasingcardiovascular risk in persons with type-2 diabetes. But our resultssuggest we should also be concerned about elevated blood sugar levelsin non-diabetics as well. An important next step is to investigatestrategies for lowering HbA1c in persons without diabetes,” said Selvin.
The study authors were supported in part by grants from the National Heart, Lung, and Blood Institute.
Co-authorsof the study are Elizabeth Selvin, Josef Coresh, Sherita H. Golden,Frederick L. Brancati, Aaron R. Folsom and Michael W. Steffes.
Materials provided by Johns Hopkins University Bloomberg School of Public Health. Note: Content may be edited for style and length.
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