Forest plot of per 1/10 increment of n-3/n-6 PUFAs ratio in diet and serum PL. Prospective studies eligible for dose–response analysis are referred to by first author and year of publication. The relative risks (RRs) are represented by the squares (the size is proportional to the weights used in the meta-analysis), and confidence intervals (CIs) are represented by the error bars. P values and I square for heterogeneity test were shown by using random effect model. The diamonds can separately represent the pooled RR for association between per 1/10 increment of dietary or serum PL ratio of n-3/n-6 PUFA and BC risk, which was combined by a two-stage random-effect model. Figure A indicated association of BC risk with per 1/10 dietary ratio of n-3/n-6 PUFA, whereas Figure B indicated association of BC risk with pre 1/10 serum PL ratio of n-3/n-6 PUFA.