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Study confirms benefits of metformin in diabetes and heart failure

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – In diabetics with heart failure, use of metformin is associated with a lower risk of mortality than use of other anti-diabetic agents, even after controlling for other potential prognostic factors, according to a March 18 online report in Diabetes Care.

In the article, Dr. Finlay A. McAlister of the University of Alberta, Canada, and colleagues note that diabetes and heart failure commonly co-exist and that outcomes are reportedly better with metformin as opposed to other agents. Whether this reflects a benefit from metformin or a harmful effect of the other medications has been unclear – but the current study suggests the latter, say its authors.

From the UK General Practice Research Database, the researchers identified 1,633 adults who were newly diagnosed with both heart failure and type 2 diabetes after January 1988 and who died before October 2007. They also identified 1,633 age- and gender-matched control subjects with diabetes and heart failure. Controls had to be alive on the date their matched case died.

The overall mean age was 78 years, and the mean duration of concurrent diabetes and heart failure was 2.8 years.

According to the article, 45% of cases and 35% of controls had no exposure to anti-diabetic drugs, including insulin. (The researchers speculate that these patients controlled their diabetes with diet and lifestyle alone.)

Compared to these individuals, current users of metformin monotherapy had a 35% lower risk of all-cause mortality (adjusted OR, 0.65). In patients who used metformin alone or as part of combination therapy, the risk of all-cause mortality was reduced by 28% (adjusted OR 0.72).

There was no association between current use of other anti-diabetic therapies (including insulin) and mortality, “although few subjects were current users of thiazolidinedione monotherapy resulting in risk estimates with very wide confidence intervals,” the authors note.

In contrast, patients taking angiotensin-converting-enzyme (ACE) inhibitors or angiotensin-receptor blockers (ARBs) had reduced mortality (adjusted OR 0.55 and 0.76, respectively). This finding confirms that “anti-failure agents proven efficacious in trials are effective when deployed in usual clinical practice in diabetic individuals,” the researchers say.

But only 18% of study patients received both an ACE inhibitor/ARB and a beta-blocker, and only 12% of those with heart failure, diabetes, and overt atherosclerosis were taking an ACE inhibitor/ARB, beta-blocker, statin and aspirin.

“The underuse of proven efficacious therapies in patients with diabetes is a common theme in health services research and does result in adverse patient outcomes,” the investigators write.

The researchers say their results extend the findings of observational studies in the U.S. and Canada. They conclude, “Until randomized trial evidence becomes available, we believe our study and the extant published literature support the use of metformin-based strategies for glucose lowering in patients with diabetes and heart failure.”

Diabetes Care 2010.