This study compares the prognostic value of glycated hemoglobin (HbA1c) and fasting glucose in identifying adults at risk for diabetes or cardiovascular disease. The research involved 11,092 non-diabetic adults without a history of diabetes or cardiovascular disease from the Atherosclerosis Risk in Communities (ARIC) study. HbA1c levels were measured in whole-blood samples collected during the second visit (1990–1992). The study found that HbA1c levels were significantly associated with the risk of newly diagnosed diabetes and cardiovascular outcomes. For example, HbA1c levels of 6.5% or higher were linked to a 16.47-fold increased risk of diabetes compared to levels of 5.0–5.5%. Similarly, higher HbA1c levels were associated with increased risks of coronary heart disease and stroke. In contrast, HbA1c and all-cause mortality showed a J-shaped association, suggesting that very low HbA1c levels may also be risky. Fasting glucose levels were not as strongly associated with cardiovascular outcomes as HbA1c. When adjusted for fasting glucose, HbA1c remained significantly associated with cardiovascular disease and mortality. The study also found that HbA1c improved risk discrimination for coronary heart disease when added to models including fasting glucose. The study concluded that in a community-based population of non-diabetic adults, HbA1c was similarly associated with the risk of diabetes and more strongly associated with cardiovascular disease and all-cause mortality compared to fasting glucose. These findings support the use of HbA1c as a diagnostic test for diabetes. The study highlights the importance of HbA1c in assessing long-term cardiovascular risk and suggests that HbA1c values exceeding 6.0% may be clinically useful for identifying individuals at risk for diabetes and cardiovascular disease. The study also notes that race did not significantly modify the associations between HbA1c and cardiovascular outcomes, despite differences in HbA1c levels between blacks and whites.This study compares the prognostic value of glycated hemoglobin (HbA1c) and fasting glucose in identifying adults at risk for diabetes or cardiovascular disease. The research involved 11,092 non-diabetic adults without a history of diabetes or cardiovascular disease from the Atherosclerosis Risk in Communities (ARIC) study. HbA1c levels were measured in whole-blood samples collected during the second visit (1990–1992). The study found that HbA1c levels were significantly associated with the risk of newly diagnosed diabetes and cardiovascular outcomes. For example, HbA1c levels of 6.5% or higher were linked to a 16.47-fold increased risk of diabetes compared to levels of 5.0–5.5%. Similarly, higher HbA1c levels were associated with increased risks of coronary heart disease and stroke. In contrast, HbA1c and all-cause mortality showed a J-shaped association, suggesting that very low HbA1c levels may also be risky. Fasting glucose levels were not as strongly associated with cardiovascular outcomes as HbA1c. When adjusted for fasting glucose, HbA1c remained significantly associated with cardiovascular disease and mortality. The study also found that HbA1c improved risk discrimination for coronary heart disease when added to models including fasting glucose. The study concluded that in a community-based population of non-diabetic adults, HbA1c was similarly associated with the risk of diabetes and more strongly associated with cardiovascular disease and all-cause mortality compared to fasting glucose. These findings support the use of HbA1c as a diagnostic test for diabetes. The study highlights the importance of HbA1c in assessing long-term cardiovascular risk and suggests that HbA1c values exceeding 6.0% may be clinically useful for identifying individuals at risk for diabetes and cardiovascular disease. The study also notes that race did not significantly modify the associations between HbA1c and cardiovascular outcomes, despite differences in HbA1c levels between blacks and whites.