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Two studies in the Sept. 21, 2004, issue of Annals of Internal Medicine find that high levels of hemoglobin A1c (glycosylated hemoglobin), a measure of blood sugar control over previous months, are an independent risk factor for cardiovascular events, such as heart disease and stroke. HA1c predicts cardiovascular disease in people with and without diabetes. HA1c levels over 7 indicate poor control of blood sugar. In people with diabetes, high levels of HA1c -- and therefore poor control of blood sugar -- are known to increase risk for eye, kidney and foot problems.
A meta-analysis of previous studies of glycosylated hemoglobin, diabetes and cardiovascular disease found the risk for cardiovascular disease increased with increasing levels of glycosylated hemoglobin (Article, p. 421). In people with type 2 diabetes, a one-percentage point absolute increase in glycosylated hemoglobin was associated with an 18 percent increase in risk for total cardiovascular disease and a 28 percent risk for peripheral vascular disease. While the study did not prove that better control of blood sugar will prevent cardiovascular disease, the study suggests a strong association of blood sugar control and the development of heart disease and stroke.
In a six-year prospective study of 10,030 people aged 45 to 79, the risk for cardiovascular disease and total mortality increased continuously as levels of hemoglobin A1c increased (Article, p. 413). There was a 21 percent increase in cardiovascular events for every one percentage point increase in hemoglobin A1c above five percent. Steep progression occurred even when data were controlled for body mass, blood pressure, cholesterol levels, diabetes and previous cardiovascular events. The level of glycosylated hemoglobin was associated with these events even in people who did not have diabetes and who had glycosylated hemoglobin levels within the normal range. This study indicates a need to investigate whether improvements in glycemic control might improve health outcomes in people who do not have diabetes.
An editorial writer says the two studies "clearly prove that the glycosylated hemoglobin level is an independent progressive risk factor for incident cardiovascular events, regardless of diabetes status" (Editorial, p. 475). "Glycosylated hemoglobin level can now be added to the list of other clearly established indicators of cardiovascular risk, such as blood pressure and cholesterol level," the writer said in the editorial.
Researchers compared 26,000 patients hospitalized with heart problems before 1998 with 31,465 heart patients who were discharged after 1998, when a new discharge form prescribing appropriate heart medications and aftercare for heart patients was instituted (Improving Patient Care, p. 446). After the change, more patients received appropriate prescriptions (such as aspirin, beta-blockers, statins, ACE inhibitors and warfarin) than before, and fewer patients died or had to come back to the hospital for heart problems within a year of discharge. The researchers conclude that a simple, inexpensive quality improvement intervention such as a new hospital discharge form can improve the chance that patients will get appropriate drugs and may improve outcomes.