Background Randomized trials of pharmacologic strength omega-3 fatty acid (n3-FA)-based therapies suggest a dose-dependent cardiovascular benefit. Whether blood n3-FA levels also mediate safety signals observed in these trials, such as increased bleeding and atrial fibrillation (AF), remains uncertain. We hypothesized that higher baseline n3-FA levels would be associated with incident bleeding and AF events in MESA (Multi-Ethnic Study of Atherosclerosis), which included a population free of clinical cardiovascular disease at baseline. Methods and Results We examined the association between baseline plasma n3-FA levels (expressed as percent mass of total fatty acid) with incident bleeding and AF in MESA, an ongoing prospective cohort study. Bleeding events were identified from review of hospitalization International Classification of Diseases, Ninth Revision (ICD-9), and International Classification of Diseases, Tenth Revision (ICD-10), codes, and AF from participant report, discharge diagnoses, Medicare claims data, and study ECGs performed at MESA visit 5. Separate multivariable Cox proportional hazard modeling was used to estimate hazard ratios of the association of continuous n3-FA (log eicosapentaenoic acid [EPA], log docosahexaenoic acid [DHA], log [EPA+DHA]) and incident hospitalized bleeding events and AF. Among 6546 participants, the mean age was 62.1 years and 53% were women. For incident bleeding, consistent statistically significant associations with lower rates were seen with increasing levels of EPA and EPA+DHA in unadjusted and adjusted models including medications that modulate bleeding risk (aspirin, NSAIDS, corticosteroids, and proton pump inhibitors). For incident AF, a significant association with lower rates was seen with increasing levels of DHA, but not for EPA or EPA+DHA. Conclusions In MESA, higher plasma levels of n3-FA (EPA and EPA+DHA, but not DHA) were associated with significantly fewer hospitalized bleeding events, and higher DHA levels (but not EPA or EPA+DHA) with fewer incident AF events.

Background and aims

High-dose eicosapentaenoic acid (EPA) therapy was beneficial in high-risk patients without clinical cardiovascular disease (CVD). Whether higher plasma levels of EPA and docosahexaenoic acid (DHA) have similar benefits in those without subclinical CVD is unclear. We aim to evaluate the interplay between plasma omega-3 fatty acids and coronary artery calcium (CAC) in relation to CVD events.

Methods

We examined 6568 participants from the Multi-Ethnic Study of Atherosclerosis (MESA) with plasma EPA and DHA levels and CAC measured at baseline. The primary outcome was incident CVD events (myocardial infarction, angina, cardiac arrest, stroke, CVD death). Hazard ratios for the primary outcome were adjusted for potential confounder using Cox regression.

Results

Mean ± SD age was 62.1 ± 10.2 years and 52.9% were females. The median follow-up time was 15.6 years. Higher log_e(EPA) (adjusted hazard ratio, aHR = 0.83; 95% CI, 0.74-0.94) and log_e(DHA) (aHR = 0.79; 95% CI, 0.66-0.96) were independently associated with fewer CVD events. The difference in absolute CVD event rates between lowest vs. highest EPA tertile increased at higher CAC levels. The adjusted HR for highest vs. lowest EPA tertile within CAC = 0 was 1.02 (95% CI, 0.72-1.46), CAC = 1-99 was 0.71 (95% CI, 0.51-0.99), and CAC≥100 was 0.67 (95% CI, 0.52-0.84). A similar association was seen in tertiles of DHA by CAC category.

Conclusions

In an ethnically diverse population free of clinical CVD, higher plasma omega-3 fatty acid levels were associated with fewer long-term CVD events. The absolute decrease in CVD events with higher omega-3 fatty acid levels was more apparent at higher CAC scores.