CHI3L1 and asthma: After categorizing included studies into different subgroups according to the ethnicity of study population, results indicated that CHI3L1 rs4950928 variant was associated with decreased asthma risk among Caucasians under the dominant model (GG + GC vs. CC: OR = 0.621, 95% CI = 0.484–0.797, P = 0.000), the codominant model (GC vs. CC: OR = 0.612, 95% CI = 0.470–0.796, P = 0.000) and the allele model (G vs. C: OR = 0.696, 95% CI = 0.567–0.856, P = 0.001) (Fig. 2).