Circulating long-chain n-3 polyunsaturated fatty acid and incidence of stroke: a meta-analysis of prospective cohort studies

Background: Circulating long-chain (LC) n-3 polyunsaturated fatty acid (PUFA) can provide objective measures that reflect both dietary consumption and relevant biological processes. Nevertheless, prospective cohort studies on circulating LC n-3 PUFA in relation to incidence of stroke have yielded inconsistent results. We therefore conducted a meta-analysis to quantitatively evaluate the association. Results: A total of 2,836 stroke events occurred among 20,460 individuals aged 35-79 yr from 10 prospective cohort studies. Circulating LC n-3 PUFA was significantly associated with reduced risk of stroke (RR: 0.86; 95% CI: 0.76, 0.98; I-2 = 0.00%), especially 22: 5n-3 (RR: 0.74; 95% CI: 0.60, 0.92) and 22: 6n-3 (RR: 0.78; 95% CI: 0.65, 0.94). The associations were more pronounced with ischemic stroke (RR: 0.81; 95% CI: 0.68, 0.96), but not with hemorrhagic stroke (RR: 0.95; 95% CI: 0.60, 1.49). A 1% increment of 22: 5n-3 and 22: 6n-3 proportions in circulating blood was associated with 25% (RR: 0.75; 95% CI: 0.64, 0.87) and 11% (RR: 0.89; 95% CI: 0.83, 0.95) reduced risk of stroke, respectively. Materials and Methods: Pertinent studies were identified from Cochrane Library, PubMed and EMBASE database through June 2017. Multivariate-adjusted risk ratios (RRs) with 95% confidence interval (CI) for incident stroke when comparing the top with the bottom tertiles of baseline LC n-3 PUFA proportions in blood were pooled using a random-effect model. Conclusions: Circulating LC n-3 PUFAs were linearly associated with reduced risk of stroke, especially 22: 5n-3 and 22: 6n-3. Such findings highlight the importance of circulating LC n-3 PUFA in the development of ischemic stroke.