Associations Between Plasma Omega-3 and Fish Oil Use With Risk of Atrial Fibrillation in the UK Biobank

Meta-analyses of randomized trials with omega-3 products found an increased risk of atrial fibrillation (AF), and a recent study from the UK Biobank concluded that fish oil supplement (FOS) use was likewise associated with increased risk of AF. Conversely, a meta-analysis based on blood levels of omega-3 fatty acids found an inverse relationship with AF risk. Thus, the relationship between omega-3 fatty acids and risk of AF remains unclear.

We conducted a retrospective analysis of UK Biobank data to link both plasma omega-3 levels and reported FOS use with AF risk. Among participants without prevalent AF, a random sample of 261 108 had data on plasma omega-3 levels and 466 169 reported about FOS use. The primary outcome was incident AF during follow-up (median, 12.7 years). Multivariable-adjusted hazard ratios (HRs [95% CIs]) for fatty acids were computed continuously (per interquintile range [IQ₅R]) and by quintile. HRs were computed for dichotomous vs. continuous FOS use.

Plasma omega-3 levels were inversely associated with incident AF (HR per IQ₅R, 0.89 [95% CI, 0.86-0.93]). FOS use was reported by 31% of the cohort and was more common in older individuals. After multivariable adjustment, no association was observed between FOS use and AF risk (HR, 1.00 [95% CI, 0.97-1.02]).

Higher circulating omega-3 levels were linked to reduced AF risk in the UK Biobank. Further, after age was adjusted for as a continuous variable (as opposed to a dichotomous variable as in an earlier report), no association was found between FOS use and risk for AF.