Fig. 2.

The exposure-response association of the composite dietary antioxidant index (CDAI) with the prevalence of chronic respiratory diseases (CRDs) by restricted cubic spline (RCS). Analyses were adjusted for covariates age (20–39, 40–59, or ≥60), sex (male or female), race (Mexican American, Other Hispanic, Non-Hispanic White, Non-Hispanic Black or Other), education level (below high school, high school, or above high school), family income-to-poverty ratio (≤1.0, 1.1–3.0, or >3.0), smoking status (never smoker, former smoker, or current smoker), drinking status (nondrinker, low-to-moderate drinker, or heavy drinker), BMI (<25.0, 25.0–29.9, or >29.9), energy intake levels (in quartiles), physical activity (inactive, insufficiently active, or active), diabetes (yes or no), hypertension (yes or no), and supplement use (yes or no).