Asthma cases demonstrated significantly higher leptin level than that in non-asthma controls among overall populations (SMD:1.061, 95% CI: 0.784–1.338, p < 10−4), Caucasians (SMD:0.287, 95% CI: 0.125–0.448, p = 0.001), Asians (SMD:1.500, 95% CI: 1.064–1.936, p < 10−4) and Africans (SMD: 8.386, 95% CI: 6.519–10.253, p < 10−4). The gene discussed is LEP; the disease is asthma.