AIP and type 2 diabetes mellitus: When AIP was transformed into categorical variables based on quartile, the adjusted ORs for T2DM in the quartiles 2, quartiles 3, and quartiles 4 were 0.93 (95% CI: 0.74, 1.18), 1.08 (95% CI: 0.85, 1.37), and 1.99 (95% CI: 1.57, 2.52), respectively, in comparison to the quartiles 1 in Model 3 (P for trend < 0.001).