(Reuters Health) - A new large study of fish oil and aspirin in people with diabetes has found that the oil supplements don’t prevent first-time heart attacks or strokes, yet aspirin does, although the benefit of aspirin therapy is canceled out by a higher risk of unwanted bleeding.

Nearly 15,500 volunteers were tested to see if either treatment made a difference. None of them had heart disease at the start of the study but all had diabetes, which typically increases the risk of cardiovascular problems two- to three-fold.

The results from the ASCEND study were reported Sunday at the European Society of Cardiology’s Annual Congress in Munich and online in The New England Journal of Medicine.

In the fish oil portion of the study, half the patients took a daily 1-gram capsule of n-3 fatty acids and the rest took a capsule containing olive oil as a placebo.

Participants were tracked for close to 7.5 years, on average. During that time, 9.2 percent of people taking the placebo died of heart disease, suffered a non-fatal heart attack or stroke, or experienced a mini-stroke known as a transient ischemic attack or TIA. The rate among fish oil recipients was 8.9 percent, a statistically insignificant difference.

Similarly, fish oil didn’t lower the risk of needing to have a blocked artery reopened. That procedure was done in 11.5 percent in the placebo group and 11.4 percent in the fish oil group.

When all causes of death were examined, the story was the same, with 9.7 percent in the fish oil group dying during the study compared with 10.2 percent with olive oil placebo, another insignificant difference.

“The study provides much-needed clarity regarding the benefits of fish oil supplements for people with diabetes but no history of cardiovascular disease,” said coauthor Dr. Louise Bowman in an email to Reuters Health. “The fish oil supplements were safe, but offered no added benefit.”

Dr. Bowman, a professor of medicine and clinical trials in the Nuffield Department of Population Health at the University of Oxford, said, “There are ongoing trials which are looking at the effects of higher doses, and so it remains to be seen whether a higher dose would be effective in preventing vascular events.”

But, she said, “a higher dose may not be so well-tolerated by patients.”

In the aspirin study, people who took 100 milligrams daily had a lower rate of cardiovascular events. The rates were 8.5 percent with aspirin and 9.6 percent with matching placebo - in this case a statistically significant difference.

But the odds of bleeding - including brain, stomach, eye or other serious bleeding - were higher as well: 4.1 percent with aspirin versus 3.2 percent with placebo.

Thus, while aspirin lowered the odds of serious cardiovascular events by 12 percent, it upped the risk of major bleeding by 29 percent.

“The absolute benefits were largely counterbalanced by the bleeding hazard,” said the team, led by Dr. Jane Armitage, Professor of Clinical Trials and Epidemiology at Nuffield.

The risk of fatal bleeding was the same in both groups.

The benefits of aspirin for people known to have heart disease are well established.

As for people without heart disease, “There is already good evidence that if you are healthy and not had any heart attacks, strokes or circulatory problems, the increased risk of bleeding from aspirin outweighs the small benefit from preventing heart attacks and strokes,” Dr. Armitage said. “We have now shown that the same applies to people with diabetes who have not had any circulatory problems.”

In general, the aspirin result “is good news for patients that they don’t have to take an extra tablet,” said Dr. Armitage. “This may allow some patients to stop aspirin and avoid the on-going risk of bleeding.”

Dr. Bowman said the ASCEND study is unique because it ” is one of the largest ever trials in diabetes and provides important information about two medical treatments, aspirin and fish oils. However, it was designed to be run extremely cost-effectively, using mail-based approaches, and so provided reliable information, relevant to the 400 million people in the world with diabetes, at a fraction of the cost of most large-scale clinical trials.”

SOURCE: bit.ly/2ockatf and bit.ly/2wpvntZ The New England Journal of Medicine, online August 26, 2018.