Association between dietary inflammation index and asthma COPD overlap

There are few studies on the relationship between dietary habits and asthma–COPD overlap (ACO). In this study, we aimed to investigate the association between dietary inflammation index (DII) score and ACO. Data from the National Health and Nutrition Examination Survey (NHANES) from 1999 to 2020. The DII score was first calculated and the demographic characteristics of the grouping based on the DII quartile were assessed. The weighted logistic regression model was used to study the relationship between DII and ACO. Subgroup analysis was used to further explore the differences in different subgroups. Restricted cubic spline (RCS) plot was used to show the general trend of DII score and disease risk, and threshold effect analysis was used to determine the inflection point. In a comparison of baseline characteristics, the highest ACO prevalence was found in the fourth quartile array of people in DII. An adjusted weighted logistic regression model showed that DII was positively correlated with the incidence of ACO. Subgroup analysis showed that the association was more pronounced in women, non-Hispanics, people with cardiovascular disease, and people without diabetes. The RCS graph shows that overall, the risk of ACO increases with the increase of DII score. Threshold effect analysis showed that the inflection point was 3.779, and the risk was more significant after the DII score was greater than the inflection point value (OR 2.001, 95% CI 1.334–3.001, P < 0.001). Higher DII scores were positively associated with ACO risk. These results further support diet as an intervention strategy for ACO prevention and treatment.