Diet Quality, Dietary Inflammatory Potential, and All-Cause Mortality in U.S. Adults With Asthma-COPD Overlap.

Asthma-COPD overlap (ACO) is associated with increased mortality and disease burden compared to asthma or COPD alone. Diet, a modifiable risk factor, influences inflammation and lung health, yet its impact on ACO mortality remains understudied. This study investigates the synergistic effects of the Healthy Eating Index (HEI-2015) and Dietary Inflammatory Index (DII) on all-cause mortality in ACO patients. Using data from the National Health and Nutrition Examination Survey (NHANES) 2007-2018, we analyzed 609 U.S. adults with ACO, defined by clinical and spirometric criteria. Dietary patterns were assessed via HEI-2015 (diet quality) and DII (inflammatory potential). Cox proportional hazards models evaluated associations with mortality, adjusting for sociodemographic, lifestyle, and clinical confounders. Restricted cubic spline analyses explored non-linear relationships, and Least Absolute Shrinkage and Selection Operator (LASSO) regression identified key dietary components for a prognostic nomogram. Healthier diets (higher HEI-2015) were associated with lower mortality risk (HR = 0.98, 95% CI: 0.97-0.99, highest quartile), while pro-inflammatory diets (higher DII) increased risk (HR = 1.13, 95% CI: 1.04-1.22). The combination of healthy and anti-inflammatory diets showed the strongest protective effect (HR = 0.68, 95% CI: 0.47-0.98). LASSO regression identified PUFA, total dairy, whole fruit, and n-6 fatty acids as key predictors, incorporated into a nomogram with moderate predictive accuracy (AUC: 0.64-0.67). Kaplan-Meier curves confirmed better survival in low-risk dietary groups (p < 0.0001). Subgroup analyses showed stronger effects in mild drinkers and non-hypertensive patients. High-quality, anti-inflammatory diets synergistically reduce mortality in ACO patients. Targeted nutritional interventions emphasizing whole fruits, dairy, and healthy fats may improve outcomes. Future research should validate these findings through interventional trials.