Meta-analysis of 15 studies including 2152 lung cancer patients revealed a positive association between high Ki-67 level and smoking history (OR = 3.087, 95%CIs: 2.504–3.806, Z = 10.56, P < 0.001; I2 = 39.40%, P = 0.064, Additional file 1: Figure S1C). The gene discussed is MKI67; the disease is lung cancer.