Composite dietary antioxidant index, chronic respiratory disease, and all-cause mortality: National Health and Nutrition Examination Survey, 2003–2018

Diet rich in antioxidant may protect against chronic respiratory disease (CRD), but few studies have evaluated the association between composite dietary antioxidant index (CDAI) and CRD. The study aimed to examine the association of CDAI with the risk of CRD and all-cause mortality in CRD patients from the US.

Data were obtained from the National Health and Nutrition Examination Survey, 2003–2018. Logistic and Cox regression analyses were used to estimate association of CDAI with CRD and all-cause mortality. Dose-response relationship was examined by restricted cubic spline analyses.

Total 44,094 participants were eligible for CRD (aged 1–85 years; mean age: 45.71 years old), and 7,685 CRD patients for all-cause mortality (median follow-up: 7.58 years; 1,136 deaths before 12/31/2019). The risk for CRD, asthma, and chronic obstructive pulmonary disease was significantly decreased by 13–32% with the increase intake of CDAI, even after adjusting for confounders (all P < 0.001). The relationship between CDAI and three respiratory endpoints was U-shaped (all P for nonlinearity < 0.001). There was an obvious declining trend in the magnitude of mortality risk with the increase of intake of CDAI, especially in patients with asthma. Fully adjusted hazard ratio was 0.72 (95% confidence interval: 0.54–0.95), 0.55 (0.42–0.72), and 0.48 (0.34–0.66) for the second, third, and fourth quartile of CDAI in patients with asthma relative to the first quartile, respectively. The association with CRD risk was significantly modified by smoking status (P-interaction: 0.006).

Our findings indicate that high CDAI is a significant protective factor against CRD and all-cause mortality in the US population.