After adjustment for BMI, associations between leptin, adiponectin and leptin/adiponectin ratio and breast cancer risk were no longer significant, while a significant positive association was observed for IL-6 (ORper SD increment = 1.32 (1.12–1.55); ORQ4vsQ1 = 1.55 (1.04–2.30), P-trend = 0.01). This evidence concerns the gene IL6 and breast cancer.