SDC1 and chronic obstructive pulmonary disease: Among the annotated genes of the DMRs and also identified in circadian entrainment pathway, in females, PER3 has been previously associated with childhood and adolescence lung function (FEV1) [35]; in males, SDC1 was found as a differentially expressed genes in COPD development by robust rank aggregation method and in KEGG pathway in the previous study [36].