Newer Blood Test Predicts Diabetes, Heart Disease – BusinessWeek
For the current study, Selvin and her colleagues measured A1C from more than 11,000 stored blood samples from the Atherosclerosis Risk in Communities Study, which began in 1990. None of the study volunteers had diabetes or cardiovascular disease at the time the blood samples were taken.
The researchers then compared the A1C levels to fasting blood sugar levels and to the 15 years of overall health follow-up information gathered for the previous study.
During that time, 2,251 people were diagnosed with diabetes, nearly 1,200 were diagnosed with heart disease and 358 people had an ischemic (non-bleeding) stroke, according to the study.
As expected, the researchers found that elevated A1C levels were associated with an increased risk of being diagnosed with diabetes. Those with an A1C of less than 5 percent had a 48 percent reduced risk of diabetes, while people whose A1Cs were between 5 and 5.5 percent had a normal risk of diabetes. From there, however, the risk quickly went up. Those with an A1C of 5.5 to 6 percent had an 86 percent increased risk of diabetes. For those between 6 and 6.5 percent, the risk more than quadrupled. For people with levels above 6.5 percent, the odds of being diagnosed were more than 16 times higher than for someone with levels under 5.5 percent. These results were similar to those for fasting glucose levels, the study authors noted.
Where fasting glucose and A1C differed greatly, however, was in the prediction of future heart disease and stroke risk. While fasting glucose failed to predict future risk, the study found that A1C levels accurately did so.
People with A1Cs under 5.5 percent had an average risk of heart disease and stroke, but for people with an A1C between 5.5 and 6 percent, the risk went up 23 percent. For those with an A1C between 6 and 6.5 percent, the risk of cardiovascular disease jumped to 78 percent. When A1C went over 6.5 percent, the risk of cardiovascular disease went up nearly twofold.
Results of the study are published in the March 4 issue of the New England Journal of Medicine.

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