B44-18 Respiratory Muscle Strength and Exercise Capacity in Adults Who Have Pre-COPD, Prism, or COPD

Introduction The characterization of pre-COPD (respiratory symptoms, risk factors, or structural abnormalities without airflow limitation) and PRISm (Preserved Ratio Impaired Spirometry; FEV1/FVC ≥ 0.70 and FEV1 < 80% predicted) phenotypes is critical for understanding the early pathophysiology of chronic obstructive pulmonary disease (COPD; FEV1/FVC < 0.70). We hypothesized that exercise capacity and respiratory muscle strength would decline progressively from pre-COPD to PRISm to COPD. This study aimed to compare these and other physiological variables among the three groups and to identify independent associations between these variables and group classification. Methods In this cross-sectional study with consecutive sampling, 150 adults (n = 50 per group) were classified by post-bronchodilator spirometry as pre-COPD, PRISm, or COPD. We measured demographics, smoking pack-years, body mass index (BMI), spirometry (including FEF25–75), maximal inspiratory/expiratory pressures (MIP/MEP), mMRC dyspnoea score, and six-minute walk distance (6MWD). Group comparisons were performed using ANOVA or Kruskal-Wallis tests with Bonferroni-adjusted post-hoc analyses. Multinomial logistic regression, adjusted for age, BMI, and 6MWD, identified independent predictors of group classification. Results The COPD group was significantly older (p < 0.001), had lower BMI (p = 0.022), and higher smoking pack-years (p < 0.001) than both the pre-COPD and PRISm groups. Significant differences were observed across groups for FEV1, FEF25–75, mMRC dyspnoea score, and 6MWD (all p ≤ 0.003). Although 6MWD and FEF25–75 declined progressively from pre-COPD to PRISm to COPD (p < 0.001), MIP and MEP did not differ among groups (p ≥ 0.198). In the multinomial logistic regression model (Nagelkerke R² = 0.301, χ² = 46,629sd = 10; p < 0.001), only age and smoking pack-years emerged as independent predictors of group classification. Each additional pack-year increased the odds of PRISm (OR = 1.025; p = 0.020) and COPD (OR = 1.029; p = 0.009), while each year of age increased the odds of COPD (OR = 1.058; p = 0.046). Functional markers, including 6MWD, were not significant independent predictors. Conclusion This cross-sectional analysis reveals a dissociation in physiological decline: exercise capacity and small-airway function deteriorated from pre-COPD to COPD, whereas respiratory muscle strength was preserved. However, only age and smoking exposure independently predicted group classification, highlighting the central role of traditional risk factors in early disease stratification. Longitudinal validation is warranted. Acknowledgment: This study was supported by a collaboration between the Turkish Thoracic Society and the American Thoracic Society through the Methods in Epidemiologic, Clinical, and Operations Research (MECOR) Program in Türkiye. This abstract is funded by: None