Fig. 1.

Representation of restricted cubic spline logistic regression models for ln-transformed copper and risk of IGR (A) and T2D (B). Knots were placed at the 20th, 40th, 60th, and 80th percentiles of ln (plasma copper concentrations). Adjusted ORs (solid line) and 95% CIs (dashed line) for IGR and T2D by ln-transformed plasma copper concentrations. Results were adjusted for sex, age (≤40, 40–49, 50–59, ≥60), BMI (≤18.5, 18.5–23.9, 24–27.9, ≥28), smoking (current, former, and never), drinking (current, former, and never), physical activity (yes or no), hypertension (yes or no), and family history of diabetes (any or none), plasma manganese, plasma magnesium, plasma iron, plasma chromium and plasma selenium.