Associations between chronotype, MTNR1B genotype and risk of type 2 diabetes in UK Biobank.

OBJECTIVE:To examine the association between the MTNR1B G risk allele, type 2 diabetes (T2D) and chronotype in the UK Biobank. METHODS:Data from the baseline investigation of the UK Biobank were utilized (n = 337 083 White British; mean age: 56.9 years; 54% women). MTNR1B rs10830963 was directly genotyped [CC (reference group), CG and GG]. Chronotype was divided into four categories: definitely morning (reference group); more morning than evening; more evening than morning; and definitely evening. Logistic regression analyses were performed to estimate odds ratios and 95% confidence intervals (CIs) for T2D, controlling for age, sex and other confounders. RESULTS:Carriers of the rs10830963 risk allele had a higher risk of T2D [CG vs. CC: OR (95% CI) 1.10 (1.07, 1.15); GG vs. CC: 1.21 (1.14, 1.29)]. Compared with definitely morning chronotype, participants with definitely evening chronotype exhibited the highest risk of T2D [1.25 (1.17, 1.33)]. Despite a nonsignificant interaction between chronotype and the risk allele [0.98 (0.94, 1.01), P = 0.176 for interaction term], we found that definitely evening chronotype (vs. definitely morning) was linked with a higher risk of T2D amongst CC and CG but not GG carriers. Additionally, we saw that the GG genotype (vs. CC) was associated with a higher risk of T2D across all chronotype categories, except for definitely evening. CONCLUSION:Our findings suggest that the MTNR1B G risk allele and late chronotype increase the risk of T2D. The association between late chronotype and higher risk of T2D appears to vary across MTNR1B rs10830963 genotypes. © 2019 The Authors. Journal of Internal Medicine published by John Wiley & Sons Ltd on behalf of Association for Publication of The Journal of Internal Medicine.

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