Association of pulmonary rehabilitation outcomes with inflammatory and nutritional status in patients with chronic respiratory diseases: a real-world retrospective cohort study

Objective This study aimed to investigate the interrelationships among pulmonary rehabilitation outcomes, systemic inflammation, and nutritional status in patients with chronic respiratory diseases, and to provide evidence supporting—but not establishing causality for—multidimensional clinical intervention strategies. Methods A real-world retrospective cohort analysis was performed on clinical records of 100 patients with chronic respiratory diseases hospitalized in the Department of Respiratory Medicine of a tertiary respiratory center in China between January 2018 and December 2022. Pre- and post-comprehensive rehabilitation (pharmacotherapy, pulmonary rehabilitation exercise, individualized nutritional support, and health education) data were collected, including pulmonary function parameters (FEV1, FVC, FEV1/FVC, TLC, and RV), six-minute walk distance (6MWD), inflammatory markers (C-reactive protein, white blood cell count, and neutrophil percentage), and nutritional indicators (body mass index, serum albumin, and total protein). Cases with >20% missing data were excluded; remaining missing values were handled by complete case analysis. Paired t-tests were used to evaluate pre-post differences, multiple linear regression to identify independent predictors of pulmonary function improvement, and Pearson correlation analysis to examine inter-variable associations. Regression covariates were selected by univariate screening at p < 0.20. Results The mean patient age was 57.74 ± 8.81 years, with 41 males (41%). Following intervention, FEV1 increased from 1.47 ± 0.43 L to 1.65 ± 0.44 L ( p < 0.001), 6MWD improved from 428.97 ± 88.59 m to 470.40 ± 92.99 m ( p < 0.001), and BMI rose from 18.15 ± 2.40 to 18.59 ± 2.47 kg/m 2 ( p < 0.001). CRP decreased from 6.85 ± 4.50 to 4.95 ± 4.71 mg/L ( p < 0.001). Seventy-six percent of patients exceeded the FEV1 minimal clinically important difference (MCID, ≥100 mL), and 63% exceeded the 6MWD MCID (≥30 m). Correlation analysis demonstrated a moderate positive association between ΔFEV1 and Δ6MWD ( r = 0.41, p < 0.001) and a significant negative association between ΔFEV1 and ΔCRP ( r = −0.21, p = 0.039). Multiple linear regression showed that no variable independently predicted ΔFEV1 after full adjustment (overall model p = 0.297); the nutritional adequacy score showed only a non-significant trend ( β = 0.024, p = 0.093), interpreted as an exploratory finding. Conclusion Comprehensive intervention was associated with significant improvements in pulmonary function, exercise tolerance, and nutritional status alongside reductions in systemic inflammation in patients with chronic respiratory diseases. The observed correlations between changes in FEV1, 6MWD, and CRP highlight potentially interrelated mechanisms, though causality cannot be established from this retrospective, uncontrolled design. These findings support multidimensional management strategies, pending validation in prospective controlled trials.