Fish oil supplements do not prevent heart attacks or strokes in patients with diabetes, according to late breaking results from the ASCEND trial presented today in a Hot Line Session at ESC Congress 2018 and published in the New England Journal of Medicine.

In observational studies, higher consumption of fish is associated with lower risks of coronary artery disease and stroke. However, previous randomised trials have not been able to show that taking fish oil supplements containing omega-3 fatty acids reduce the risk of having cardiovascular events.

The ASCEND trial (A Study of Cardiovascular Events iN Diabetes) examined whether fish oil supplements reduce the risk of a cardiovascular event in patients with diabetes. Between 2005 and 2011, 15,480 patients with diabetes but no history of cardiovascular disease were randomly assigned to fish oil supplementation (1 g daily) or matching placebo.

The primary efficacy outcome was first serious vascular event, which included non-fatal heart attacks, non-fatal strokes or transient ischaemic attacks (sometimes called “mini-strokes”), or deaths from a cardiovascular cause (but excluding any intracranial haemorrhage, i.e. bleeding in the head or brain).

During an average of 7.4 years of follow-up, a first serious vascular event occurred in 689 (8.9%) participants allocated fish oil supplements and 712 (9.2%) participants allocated placebo. There was no significant difference between the two groups: rate ratio of 0.97 (95% confidence interval 0.87–1.08; p=0.55).

Professor Louise Bowman, principal investigator, Nuffield Department of Population Health, University of Oxford, UK, said: “Our large, long-term randomised trial shows that fish oil supplements do not reduce the risk of cardiovascular events in patients with diabetes. This is a disappointing finding, but it is in line with previous randomised trials in other types of patient at increased risk of cardiovascular events which also showed no benefit of fish oil supplements. There is no justification for recommending fish oil supplements to protect against cardiovascular events.”

The study was funded by: the British Heart Foundation, Medical Research Council Population Health Research Unit (MRC-PHRU), Bayer AG, Solvay, Abbott and Mylan. It was designed and run independently of the funders by the Clinical Trial Service Unit & Epidemiological Studies Unit (CTSU) in the Nuffield Department of Population Health (NDPH). The lead investigators abide by the CTSU guidelines not to accept payment or honoraria from drug companies.