MONTREAL — No difference in mortality was found at 4 years between baseline hemoglobin A1c levels of less than 6.5% and levels of 6.5%-7.0% in a prospective observational study of nearly 3,000 unselected patients with type 2 diabetes.
However, the Diabetes in Germany study also found a dramatically increased risk of mortality for those with baseline HbA1c levels greater than 8%, compared with those who began the study with lower HbA1c values. Other baseline predictors of mortality included age, smoking, cardiovascular disease, and systolic blood pressure, Dr. Markolf Hanefeld reported at the World Diabetes Congress.
“In a diabetes population rather well controlled for hemoglobin A1c, smoking status and good blood pressure control are of utmost importance for survival. However, at a level greater than 8%, [the degree of] glucose control becomes a serious risk factor for all-cause mortality,” said Dr. Hanefeld of the Center for Clinical Studies, Technical University, Dresden, Germany.
Of an initial 4,020 unselected patients aged 35-80 years with type 2 diabetes in Germany, 2,784 completed the study at a median of 3.7 years; 175 died during that time. Most (86%) had no history of major cardiovascular events (MACE) at baseline; 251 (8.5%) reported a first MACE during follow-up. Average baseline HbA1c for the entire group was 7.0%. Thirty-seven percent met the International Diabetes Federation's and American Association of Clinical Endocrinologists' target HbA1c of less than 6.5%; 57% met the American Diabetes Association's target of less than 7.0%. But 29% had values above 7.5%. The average HbA1c level for the entire group did not change over the 4-year period, Dr. Hanefeld said.
Among those who died during the study period, 6% had baseline HbA1c values of less than 6.5%; 5.3% had values of 6.5%-6.9%; 5.1% had values of 7.0%-7.9%; and 7.6% had values of 8% or higher. The same trend was seen in MACE.
In a multivariate analysis, the most significant factor predicting mortality was MACE at baseline, conferring a twofold greater risk. Also significant were smoking, age, and systolic blood pressure. Female gender cut the risk by half. Hemoglobin A1c did not contribute significantly to mortality, he said.
A comparison of these findings with the standard care arms of the randomized, controlled glucose-lowering trials ADVANCE, ACCORD, and VADT shows no link between HbA1c and mortality.
Dr. Hanefeld stated that he had no conflicts of interest.