RBP4 and type 2 diabetes mellitus: To our best knowledge, only two cohort studies have examined the association between RBP4 and type 2 diabetes risk in general populations: the Atherosclerosis Risk in Communities (ARIC) study reported a positive association only in women, but not in men or total study population [16]; while a cohort study among a Chinese population observed a positive association in total study participants but did not examine potential heterogeneity by sex [17].