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

Background 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. Methods 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 [IQ 5 R]) and by quintile. HRs were computed for dichotomous vs. continuous FOS use. Results Plasma omega‐3 levels were inversely associated with incident AF (HR per IQ 5 R, 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]). Conclusions 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.