Habitual fish oil supplementation and the risk of incident atrial fibrillation: findings from a large prospective longitudinal cohort study

Aims: Mixed effects of fish oil supplementation on the risks of atrial fibrillation (AF) were observed in several large-scale randomized controlled trials. Whether this relationship would be modified by genetic AF risk, baseline cardiovascular disease (CVD) status and background oily fish consumption are unknown.

Methods and results: We included 468 665 participants without AF at baseline from the UK Biobank cohort. The association between fish oil supplementation and the AF risk was assessed in the study cohort and in several subgroups, including genetic AF predisposition, baseline CVD status, and background oily fish consumption. During a median follow-up of 11.1 years, fish oil users had a higher rate of incident AF (6.2% vs. 5.2%, adjusted hazard ratio of 1.10, and 95% confidence interval of 1.07, 1.13). Compared with non-users, fish oil users had a higher rate of incident AF in the low (3.7% vs. 3.0%, P= 0.02), intermediate (5.8% vs. 4.8%, P < 0.0001), and high (9.8% vs. 8.1%, P < 0.0001) genetic AF risk groups. In participants without CVD at baseline, fish oil users had a higher rate of incident AF (5.3% vs. 4.1%, P < 0.0001), which was not observed in participants with CVD at baseline (11.6% vs. 11.1%, P = 0.56), with significant interaction (P-interaction < 0.0001). The association between fish oil supplementation and the AF risk was not modified by background oily fish consumption (P-interaction = 0.62).

Conclusion: Habitual fish oil supplementation was associated with the risk of incident AF, regardless of genetic AF predisposition and background oily fish consumption. This association was observed only in individuals without CVD at baseline.