LEP and lung cancer: At first, we carried out a subgroup analysis by language (English or Chinese), but we found no statistical significance between serum leptin concentrations and lung cancer regardless of whether the studies were published in English or in Chinese (SMD=-0.33 95%CI=-1.21–0.54, P=0.456; SMD=0.33, 95%CI=-0.60–1.26, P=0.487, respectively).