Association between the comprehensive dietary antioxidant index and adult asthma: A cross-sectional study based on NHANES 2003 to 2018.

Increasing evidence suggests that oxidative stress plays a key role in the pathogenesis of asthma; however, research on the association of the comprehensive dietary antioxidant index (CDAI) with asthma remains limited. Therefore, this study aims to explore the association between CDAI and asthma. Data from the National Health and Nutrition Examination Survey (NHANES) (2003-2018) were analyzed to examine the association between CDAI, derived from two 24-hour dietary recalls, and asthma, defined by self-reported physician diagnosis. Logistic regression was used to examine the overall association, while restricted cubic spline models were applied to explore potential nonlinear relationships. A total of 35,945 adult participants were included, with 14.2% diagnosed with asthma. In the unadjusted model, higher CDAI levels, particularly within a moderate range, were generally associated with a lower risk of asthma. After adjustment for potential confounders, the highest CDAI quartile showed lower odds of asthma than the lowest quartile; however, this comparison did not reach statistical significance (odds ratio = 0.88, 95% confidence interval: 0.76-1.02; P = .078). Importantly, restricted cubic spline analysis demonstrated a significant nonlinear association between CDAI and asthma (P for nonlinearity <.05), with asthma risk declining at moderate CDAI levels and rising at very high levels. Subgroup analyses showed stronger protective effects among adults aged 40 to 60 years, females, non-Hispanic Blacks, other Hispanic populations, former smokers, and individuals with obesity. Sensitivity analyses indicated that most individual dietary antioxidants exhibited nonlinear associations with asthma, except for vitamin A. CDAI is nonlinearly associated with asthma risk, with moderate levels generally reducing risk, while very high intake may diminish this benefit, highlighting the role of antioxidant-rich diets in asthma prevention. Future prospective cohort studies and mechanistic investigations are warranted to clarify causal relationships and to determine optimal dietary antioxidant intake ranges for asthma prevention.