Summarized dose–response association between dietary ratio of n-3/n-6 PUFAs and risk of breast cancer. Adjusted RRs from each exposure quantile of dietary ratio of n-3/n-6 PUFAs in included individual studies were represented by the gray diamonds, and corresponding intervals (CIs) were represented by the lightgray trendline. The dash line indicated that dose–response linear trend (P
trend = 0.012) between dietary ratio of n-3/n-6 PUFAs and risk of breast cancer by use of variance-weighted least squares regression of fixed effect model; the black curve indicated nonlinear (curvilinear) trend (P
trend = 0.018) by use of restricted cubic splines functional model with three knots at percentiles 25%, 50%, and 75% of the distribution.