Poor HbA1c Control Raises HF Risk in Type 1


Major Finding: The incidence of heart failure in type 1 diabetes patients rose as HbA1c levels did, from 1.42 to 5.20 per 1,000 patient-years in patients with HbA1c levels of below 6.5% and at least 10.5%, respectively.

Data Source: An analysis of 20,985 type 1 diabetes patients aged at least 18 with no known heart failure in the Swedish national diabetes registry, who were registered during 1998-2003 and followed through 2009.

Disclosures: The study was supported by an unrestricted grant from AstraZeneca, Novo Nordisk Scandinavia, the Swedish Heart and Lung Foundation, and the Swedish Research Council. Dr. Lind has received honoraria from or been a consultant for Bayer, Eli Lilly, Novartis, Novo Nordisk Scandinavia, Medtronic, Pfizer, and Sanofi-Aventis; and has been a member of an advisory board for Novo Nordisk Scandinavia.

SAN DIEGO – Tight control of hemoglobin A1c levels significantly reduces the risk of heart failure in patients with type 1 diabetes, results from a large, long-term study show.

In fact, patients with very poor glycemic control were four times as likely to experience heart failure, compared with their counterparts with optimal glycemic control.

“Because treatment for heart failure improves survival and quality of life, clinicians should be observant of signs of heart failure in management of patients with type 1 diabetes, starting at an early stage,” lead author Dr. Marcus Lind wrote in the study, which was presented at the meeting and simultaneously published onlinei “Echocardiography might be warranted, especially in the presence of poor glycemic control, long duration of diabetes, or an adverse risk factor profile.”

Dr. Lind of the department of medicine at Uddevalla (Sweden) Hospital and his associates used the Swedish national diabetes registry to identify 20,985 patients aged 18 years or older with type 1 disease who had no known heart failure and who were registered between January 1998 and December 2003. They followed the cohort until hospital admission for heart failure, death, or end of follow-up on Dec. 31, 2009 (Lancet 2011 June 25 [doi: 10.1016/S0140-6736(11)60471-6]).

The incidence of heart failure was determined by dividing the number of patient-years of follow-up in a particular HbA1c category, reported as events per 1,000 years of follow-up. The six HbA1c categories were less than 6.5%, from 6.5% to less than 7.5%, from 7.5% to less than 8.5%, from 8.5% to less than 9.5%, from 9.5% to less than 10.5%, and 10.5% or greater. Cox regression analysis was used to study possible associations between heart failure and patients' characteristics.

The mean age of patients was 39 years, and 45% were female; they had had diabetes for a mean of 14 years, and their mean body mass index was 25 kg/m

After adjustment for age, sex, duration of diabetes, cardiovascular disease risk factors, acute myocardial infarction, and other comorbidities, a Cox regression analysis revealed that patients with an HbA1c level of 10.5% or higher were four times more likely to develop heart failure than were those who had an HbA1c level of less than 6.5%.

Other independent predictors of heart failure included age (hazard ratio, 1.64 per 10-year increase); duration of diabetes (HR, 1.34 per 10-year increase); BMI (HR, 1.05 per 1-kg/m

“For many years there have been observations that poor glycemic control is linked to heart attack and cardiovascular mortality,” Dr. Sue Kirkman, senior vice president of medical affairs and community information for the American Diabetes Association, said in an interview at the meeting. “This may be the first time that it's been shown to be linked to heart failure in a type 1 population.”

She called the study “hypothesis generating,” and noted that a long-term randomized trial will be needed to confirm the findings. “It is interesting, because it seems that in type 1 diabetes there may be a stronger link between glucose lowering and cardiac outcomes than in type 2 diabetes,” she said.

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Tight Control 'Essential'

How tightly should glycemia be controlled in diabetes? The clear message from Dr. Lind's and his colleagues' paper is that tight control of glycemia in type 1 diabetes is essential, especially now that they have shown that such control can prevent heart failure, besides other aspects of cardiovascular disease. In the future, even established type 1 diabetes cardiomyopathy might be rescued by gene-activated prosurvival paths, as shown in a mouse model. Only in developing countries, where tight control is often not feasible, could less-strict control be acceptable for type 1 diabetes.

LIONEL H. OPIE, M.D., is director of the Hatter Cardiovascular Research Institute at the University of Cape Town (South Africa). This was adapted from an accompanying commentary published online (Lancet 2011 June 25 [doi: 10.1016/S0140-6736(11)6078703]). He reported no conflicts of interest.

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