Xin Zhang ^1,2* Jipeng Mo ^1,2* Kaiyu Yang ^1,2* Tiewu Tan ^1,3* Hui Qin ^1,3* Cuiping Zhao ^1,4*

• ¹ Nanjing Medical University, Nanjing, China
• ² Emergency Medicine, Changzhou No.2 People's Hospital, Changzhou, Jiangsu Province, China
• ³ Intensive Care Medicine, Changzhou No.2 People's Hospital, Changzhou, Jiangsu Province, China
• ⁴ Geriatrics, Changzhou No.2 People's Hospital, Changzhou, Jiangsu Province, China

Background: Recent research has identified the Low-Carbohydrate Diet (LCD) score as a novel biomarker, with studies showing that LCDs can reduce carbon dioxide retention, potentially improving lung function. While the link between the LCD score and chronic obstructive pulmonary disease (COPD) has been explored, its relevance in the U.S. population remains uncertain. This study aims to explore the association between the LCD score and the likelihood of COPD prevalence in this population.Methods: Data from 16,030 participants in the National Health and Nutrition Examination Survey (NHANES) collected between 2007 and 2023 were analyzed to examine the relationship between LCD score and COPD. Propensity score matching (PSM) was employed to reduce baseline bias. Weighted multivariable logistic regression models were applied, and restricted cubic spline (RCS) regression was used to explore possible nonlinear relationships. Subgroup analyses were performed to evaluate the robustness of the results. Additionally, we employed eight machine learning methods-Boost Tree, Decision Tree, Logistic Regression, MLP, Naive Bayes, KNN, Random Forest, and SVM RBF-to build predictive models and evaluate their performance. Based on the best-performing model, we further examined variable importance and model accuracy.Results: Upon controlling for variables, the LCD score demonstrated a strong correlation with the odds of COPD prevalence. In compared to the lowest quartile, the adjusted odds ratios (ORs) for the high quartile were 0.77 (95% CI: 0.63, 0.95), 0.74 (95% CI: 0.59, 0.93), and 0.61 (95% CI: 0.48, 0.78). RCS analysis demonstrated a linear inverse relationship between the LCD score and the odds of COPD prevalence. Furthermore, the random forest model exhibited robust predictive efficacy, with an area under the curve (AUC) of 71.6%.Conclusions: Our study of American adults indicates that adherence to the LCD may be linked to lower odds of COPD prevalence. These findings underscore the important role of the LCD score as a tool for enhancing COPD prevention efforts within the general population. Nonetheless, additional prospective cohort studies are required to assess and validate these results.