"This new analysis does not answer the question whether the observed increase in heart failure leads to other serious complications, including death," Nissen said. "The authors did not examine the risk of cardiac death in patients who developed congestive heart failure while taking a TZD drug. Instead, they looked at overall cardiovascular mortality. This finding neither confirms, nor refutes, the hypothesis that TZDs lead to major complications of heart failure, including death," he said.
And concentrating on the risks, rather than the benefits, of these drugs misses the point, another expert said. The real question, according to Dr. Victor Montori, is whether these drugs are of any benefit at all to patients.
Right now, it's a matter of faith that lowering blood sugar really prevents the complications of type 2 diabetes, said Montori, an associate professor of medicine at the Mayo Clinic in Rochester, Minn., and co-author of an accompanying journal editorial.
There haven't yet been any large, extended clinical trials that measure the outcomes that really matter to diabetic patients, Montori said. Those outcomes include feeling better and living longer, he said. "Therefore, clinicians and patients cannot have a discussion with confidence about the potential benefits and downsides of currently available diabetes medications," he said.
Montori believes that, right now, it's not clear that the blood sugar reductions seen with these drugs actually prevent diabetes complications such as heart disease. The proof that reducing blood sugar prevents the complications of diabetes is based on evidence from patients with the much rarer, inherited type 1 diabetes which is usually treated with insulin, he said.
"That same proof is much shakier in patients with type 2 diabetes." Montori said. "And it seems that it matters with which drug you lower blood sugar in patients with type 2 diabetes."
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