Correlation Between Vitamin D, Inflammatory Markers, and T Lymphocytes With the Severity of Chronic Obstructive Pulmonary Disease and its Effect on the Risk of Acute Exacerbation: A Single Cross-sectional Study

•Lower 25-hydroxyvitamin D level and higher inflammatory level may be an adverse prognostic factor for patients with chronic obstructive pulmonary disease (COPD).•Vitamin D affects COPD by affecting inflammatory cytokines and T lymphocyte levels.•The nomogram model in our study can be used in daily clinical practice to predict the risk of acute exacerbation and hospitalization in patients with COPD. Chronic obstructive pulmonary disease (COPD) will become the fourth largest cause of death of chronic diseases in the world in 2030. The incidence of COPD ranked top among chronic diseases in the world. At present, there is a lack of simple and effective drugs for the treatment of COPD and for slowing the progression of the disease. The application of vitamin D as a drug in clinical treatment has been a research hotspot. In this study, we investigated the correlation between serum 25-hydroxyvitamin D (25(OH)D), inflammatory markers, and T lymphocytes with the severity of COPD and its effect on the risk of acute exacerbation. In this study, we recruited hospital inpatients and outpatient clinic patients with COPD. Their levels of 25(OH)D, inflammatory markers, and T lymphocytes were assessed. We built a nomogram model to evaluate the risk of acute exacerbation of COPD. The inflammatory mediators were higher in patients with acute exacerbation of COPD (AECOPD) than those in patients with COPD, but 25(OH)D showed the opposite phenomenon. In logistic regression analysis, high levels of neutrophil-lymphocyte ratio, C-reactive protein, and partial pressure of carbon dioxide and low levels of vitamin D, partial pressure of oxygen, and forced expiratory volume in the first as a percentage of predicted were regarded as independent risk factors for AECOPD. These variables were used for the construction of the nomogram model. The AUCs of the model were 0.971 (95% CI, 0.952–0.989), and 0.981 (95% CI, 0.959–1.000) in the training and testing set respectively, demonstrating that the model exhibited high accuracy for the prediction of the risk of acute exacerbation of COPD. The calibration curve of the nomogram found a high degree of consistency between the expected and actual values. The decision curve analysis and clinical impact curve indicated that the nomogram has clinical applicable for patients with COPD. A considerable percentage of patients with COPD were found to have insufficient vitamin D levels. Patients with AECOPD reported more symptoms than those with COPD. Th