The research is in and it points to an increased risk of heart failure, heart attacks and death among patients taking diabetes drugs like Avandia (rosiglitazone).

The glitazone class of drugs to which Avandia belongs also includes Actos (pioglitazone).

Following on the heels of clinical trials and smaller studies that linked the drugs to heart problems earlier this year, Canadian researchers monitored all Ontario residents (159,026 people) over the age of 65 who were taking glitazones for diabetes between 2002 and 2006.

They tracked the incidence of hospital visits for congestive heart failure, as well as hospital visits for heart attacks and deaths. The effects of other diabetes drugs the group was taking were also noted.

The findings are published in the Dec. 12 issue of the Journal of the American Medical Association.

When the effects of Avandia and Actos were compared to the other drugs, researchers found that patients experienced a 60 per cent relative increase in heart failure, a 40 per cent relative increase in heart attacks and a 30 per cent relative increase in death.

Viewed another way, that risk means that in a group of 100 people, taking Avandia or Actos would result in three more cases of heart failure than in a group not taking the medications, four additional heart attacks and five additional deaths, over a four-year period in people over 65.

They found that the drugs are also associated with weight gain and edema, swelling caused by fluid in the body's tissue.

The researchers urge caution despite the findings. "We don't want people to panic. Treatment decisions must remain individualized with doctors and patients weighing the potential harms and benefits of these drugs, especially when used among the elderly who are at higher risk of cardiac complications," said Dr. David Alter, co-author and senior scientist with the Institute for Clinical Evaluative Sciences.

The researchers admit that the population sampled was of an older age and they cannot be certain a younger group of patients would have experienced the same risks.

On Nov. 14, the U.S. Food and Drug Administration issued a black box warning about heart attack risks for Avandia — the most severe type of warning the agency can require — pending further research.

The authors of the current study feel that the missing data the FDA sought can be found in their study. "Their review of the evidence found that the association between rosiglitazone and adverse cardiac events was mainly based on clinical trials not specifically designed to examine cardiac events or small observational studies of short duration," they write.

"Our large, well-designed population-based study provides more convincing evidence that rosiglitazone is associated with an increased risk of cardiac events and deaths among elderly patients with diabetes."

Health Canada issued an advisory in May, telling patients with underlying heart disease to consult their doctor if taking Avandia. It also warned patients with diagnosed heart problems to avoid using the medication.