Patients receiving maintenance haemodialysis have a cardiovascular mortality rate more than 20 times higher than the general population, and many standard preventative therapies have proven ineffective in this high-risk group. The results of a new randomised clinical trial, PISCES, suggest that daily supplementation with fish oil could offer a significant benefit, substantially reducing the rate of serious cardiovascular events.¹˒²

The PISCES trial was a double-blind, randomised, placebo-controlled study involving 1228 adult patients on maintenance haemodialysis at 26 sites in Canada and Australia. Participants were assigned 1:1 to receive either a daily 4 g dose of fish oil, containing 1.6 g of eicosapentaenoic acid (EPA) and 0.8 g of docosahexaenoic acid (DHA), or a matching corn-oil placebo. The trial followed patients for a median of 3.5 years. The primary endpoint was a composite of all serious cardiovascular events, defined as sudden and non-sudden cardiac death, fatal and non-fatal myocardial infarction (MI), peripheral vascular disease leading to amputation, and fatal and non-fatal stroke.¹

The study met its primary endpoint, showing a significantly lower rate of serious cardiovascular events in the fish oil group compared to the placebo group (0.31 vs 0.61 per 1000 patient-days). This translated to a 43% lower risk for those taking fish oil (hazard ratio [HR], 0.57; 95% CI, 0.47–0.70; P<0.001). The benefit was observed in patients both with and without a prior history of cardiovascular events. According to first author Dr Charmaine E. Lok, University of Toronto, Canada, “patients who took fish oil and had experienced a prior cardiovascular event actually had the same risk as a placebo patient who did not have a previous cardiovascular event.”² Secondary endpoints also favoured the fish oil group, with lower rates of cardiac death (HR, 0.55), fatal and non-fatal MI (HR, 0.56), and fatal and non-fatal stroke (HR, 0.37). Regarding safety, serious bleeding events occurred in 4.8% of the fish oil group versus 7.6% of the placebo group, with no other meaningful differences in adverse events.¹

Commenting on the findings, Dr David Charytan, NYU Grossman School of Medicine, New York, USA, called the study a "major achievement," noting it is "the first large outcome study to show a cardiovascular risk reduction in dialysis patients.”² The results suggest that n-3 fatty acid supplementation could be a valuable and accessible therapy to mitigate the high cardiovascular burden in this patient population.

Despite the positive results, experts advise a degree of caution. Dr Charytan emphasised the need for further research to validate the findings. “We should not stop at one study. We need more data from a large, well-powered trial to confirm these results and get a better understanding,” he concluded.²

This study was funded by the Heart and Stroke Foundation of Canada, the Lawson Health Research Institute, the Peter Munk Cardiac Care Innovation Fund, the Kidney CARE Network International, the National Health and Medical Research Council, and a private donation.

References

1. Lok CE, Farkouh M, Hemmelgarn BR, et al. Fish-Oil Supplementation and Cardiovascular Events in Patients Receiving Hemodialysis. N Engl J Med. 2025. https://doi.org/10.1056/NEJMoa2513032.

2. Melville NA. Fish Oil Shows Cardiovascular Benefits in Dialysis Patients. Medscape. 8 November 2025. https://www.medscape.com/viewarticle/fish-oil-shows-cardiovascular-benefits-dialysis-patients-2025a1000uze?src=rss.

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