In the subgroup analysis of ethnicity, we found no association between serum leptin concentrations and lung cancer in Chinese people (SMD=0.50, 95%CI=-0.17–1.17, P=0.144) and in Europeans (SMD=-0.70, 95%CI=-1.79–0.39, P=0.208) (Figure 2). Here, LEP is linked to lung carcinoma.