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Fish oil supplement use and atrial fibrillation

Whether fish oil supplement use affects the risk of incident atrial fibrillation was examined in a large UK prospective cohort study

Fish oil supplement use in patients with cardiovascular disease has been shown to provide a small beneficial advantage in terms of mortality and admission to hospital for cardiovascular reasons in patients with heart failure. However, not all studies with fish oils has have been positive.

For instance, other data in patients with atherogenic dyslipidaemia and high cardiovascular risk, have found that among statin-treated patients at high cardiovascular risk, the addition of omega-3 fatty acids, resulted in no significant difference in a composite outcome of major adverse cardiovascular events when compared with corn oil.

Despite these ambiguous findings with respect to cardiovascular disease, there is some evidence that fish oil supplement use among patients with atrial fibrillation (AF) is beneficial. For example, in one trial among patients with persistent atrial fibrillation on amiodarone and a renin-angiotensin-aldosterone system inhibitor, the addition of fish oil supplementation improved the probability of maintaining sinus rhythm after direct current cardioversion, possibly through prevention of atrial fibrillation recurrence.

In contrast, a recent study with both fish oils and vitamin D supplementation observed that compared with placebo, neither supplement had a significant effect on the risk of incident atrial fibrillation over a follow-up of more than 5 years. But when data has been pooled, one 2021 meta-analysis found that fish oil supplement use was associated with an increased risk of AF which was greater in trials testing >1 g/d.

With some evidence to suggest that both monogenic and polygenic factors contribute to AF risk in the general population, in the present study, a team of Australian researchers sought to examine whether habitual fish oil supplement use was associated with the risk of incident AF after adjustment for several factors including individual’s genetic risk score.

Using the UK Biobank data, individuals were dichotomised (Yes/No) as habitual fish oil users. After calculation of an AF genetic risk score, individuals were categorised to be at either low, immediate or high genetic risk.

The primary outcome of the study was set as incident AF and the researchers also considered the risk of AF in those with and without cardiovascular disease at the study baseline point. The results were adjusted for several factors including age, gender, consumption of oily fish and genetic risk score.

Fish oil supplement use and incident atrial fibrillation

A total of 468,665 individuals with a mean age of 56.5 years (45.2% male) were included in the analysis and followed for a median of 11.1 years.

During the period of follow-up, the risk of developing incident AF was significantly higher among fish oil supplement users (adjusted hazard ratio, aHR = 1.10, 95% CI 1.07 – 1.13, p < 0.0001).

When considering the risk of AF based on genetic risk scores, this was significantly higher for low (HR = 1.08), intermediate (aHR = 1.10) and high risk (aHR = 1.11) fish oil supplement users.

Finally, while there was no increased risk among those with existing cardiovascular disease (CVD), the risk was elevated (aHR = 1.13) among those without CVD at baseline.

The authors concluded that habitual fish oil supplement use was associated with a higher risk of incident atrial fibrillation and that this risk remained regardless of genetic AF risk and consumption of oily fish but was only observed in those without cardiovascular disease.

Zhang J et al. Habitual fish oil supplementation and the risk of incident atrial fibrillation: findings from a large prospective longitudinal cohort study Eur J Prev Cardiol 2022