Tan X, et al. - Researchers used data from the baseline investigation of the UK Biobank, to determine the link between the MTNR1B G risk-allele, type 2 diabetes (T2D), and chronotype. The study sample included 337,083 White British, with a mean age of 56.9 years, 54% were women. They directly genotyped MTNR1B rs10830963 (CC (reference group), CG, and GG). Four groups of chronotype were defined: definitely morning (reference group); more morning than evening; more evening than morning; and definitely evening. They noted that although the interaction between chronotype and the risk allele was non-significant, there was an association of definitely evening chronotype (vs definitely morning) with a higher risk of T2D among CC and CG but not GG carriers. Across all chronotype groups, except for definitely evening, a higher risk of T2D was observed in relation to the GG genotype (vs CC). Overall, an increased risk of T2D was reported in relation to MTNR1B G risk-allele and late chronotype. The link between late chronotype and higher risk of T2D seemed to differ across MTNR1B rs10830963 genotypes.