ORLANDO — Higher levels of hemoglobin A1c significantly boosted the risk of heart failure in patients with diabetes in an analysis of more than 1,800 patients.
This association was seen even in patients with diabetes who did not have clinically apparent coronary heart disease (CHD), which suggests that poorly controlled hyperglycemia plays a direct role in causing heart failure, Dr. Antonio Pazin-Filho, an epidemiologist at Johns Hopkins University, Baltimore, said at a conference on cardiovascular disease epidemiology and prevention sponsored by the American Heart Association. The likely mechanism for this link is an increased risk of diabetic cardiomyopathy in patients with poorly controlled hyperglycemia, he said.
“The message is that patients with diabetes may benefit more if they can reach their glycemia goal,” noted Dr. Peter W.F. Wilson, professor of medicine at Emory University in Atlanta. The data also suggested the risk of heart failure from hyperglycemia was the highest in patients treated with insulin, suggesting that diabetic patients on insulin face the biggest risk from heart failure if they cannot maintain good glycemic control, Dr. Wilson said in an interview.
The study used data collected from people in the Atherosclerosis Risk in Communities study, a prospective study of nearly 16,000 people from four communities in the United States that began in 1987. The analysis by Dr. Pazin-Filho and his associates focused on 1,827 subjects diagnosed with diabetes during 1990–1992. These patients were followed for about 10 years, through the end of 2002. At baseline, 1,668 patients did not have CHD and 159 did.
During follow-up, 205 of the patients without CHD developed heart failure, defined as a first hospitalization for heart failure or death because of heart failure. Incident heart failure also occurred in 50 patients who had CHD at baseline. The 205 people who developed heart failure without preexisting CHD were further divided into 118 who developed heart failure without first being diagnosed with clinically apparent CHD during follow-up, and 87 who were first diagnosed with CHD during follow-up before their heart failure appeared.
The researchers then analyzed the risk these patients faced for developing heart failure relative to their serum level of hemoglobin A1c at baseline. The results showed that in patients with diabetes who did not have preexisting CHD, the risk of later developing heart failure was significantly linked to their HbA1c level. For each 1% increase in HbA1c at baseline, the risk of heart failure rose by 13% in an analysis that controlled for potential confounding factors at baseline including age, gender, race, education, health-insurance status, alcohol intake, smoking status, blood pressure, and serum lipid levels.
When the analysis excluded the 87 people who developed CHD before heart failure during follow-up, the link between baseline levels of Hb A1c and risk for heart failure was even stronger: For every 1% increase in serum HbA1c, the risk of heart failure rose by 15%, also a statistically significant effect.
However, in the patients who had preexisting CHD at baseline, the analysis showed no significant relationship between HbA1c levels and the risk of developing heart failure.
The usual goal for patients with diabetes is a serum level of HbA1c of 7% or less; normal levels are 6% or less. In Dr. Pazin-Filho's findings, the highest incidence of heart failure was in patients with a baseline level of more than 8%.