Association between the composite dietary antioxidant index and prevalence of kidney stone disease in adults: A nationally representative cross-sectional study

Background Individual dietary antioxidants have been shown to be protective factors against kidney stone disease (KSD). However, the correlation between the composite dietary antioxidant index (CDAI), a reliable indicator for the total dietary antioxidant intake, and KSD has not yet been investigated. Objectives To evaluate the association between the CDAI and prevalence of KSD in American adults. Methods This cross-sectional analysis utilized data from the National Health and Nutrition Examination Surveys (NHANES) 2007–2018. Participants aged ≥ 20 years with a self-reported history of KSD and CDAI were included. Weighted proportions and multivariate regression models were used to study the independent relationship between KSD and CDAI. Generalized additive model (GAM) and smooth curve fitting were performed to explore the potential non-linear correlation, and a two-piecewise linear regression model was then applied to examine the threshold effect and to calculate the turning point. Results A total of 29 763 adults were included, with a mean CDAI of 0.64. The prevalence of KSD was 10.02 %. Multivariate regression analysis indicated that the CDAI was negatively correlated with KSD [OR(95 %CI) = 0.979 (0.962, 0.996),p = 0.018]. Compared to participants in the lowest CDAI quartile, those in the highest CDAI quartile had a significantly lower kidney stone prevalence [OR(95 %CI) = 0.786 (0.667, 0.926),p = 0.004]. Smooth curve fitting and piecewise linear regression suggested that the turning point of the CDAI was 4.146. When the CDAI was less than 4.146, the prevalence of KSD decreased by 4.5 % for every 1 unit increase in CDAI [OR(95 %CI) = 0.955 (0.933, 0.978), p < 0.001]. However, when the CDAI was greater than 4.146, the prevalence increased by 3.6 % for every 1 unit increase in the CDAI [OR(95 %CI) = 1.036 (1.002, 1.076), p = 0.041]. Conclusions There was a U-shaped association between the CDAI and KSD. Both low and high CDAI scores were associated with a higher prevalence of KSD. When the CDAI was controlled at approximately 4.146, the risk of KSD was the lowest. These results suggest that maintaining an appropriate CDAI by planning dietary antioxidant components may help to prevent and control KSD.