Objective Exploring the risk factors for sarcopenia in elderly patients with chronic obstructive pulmonary disease (COPD) and constructing a risk prediction nomogram model. Methods A retrospective study was conducted on elderly COPD patients admitted to the General Internal Medicine Department of Tianjin Hospital in Tianjin from January 2024 to December 2024. They were divided into a sarcopenia group and a non-sarcopenia group based on the presence of sarcopenia. General data of the two groups were compared, and logistic regression analysis was used to identify risk factors for sarcopenia in elderly COPD patients. The diagnostic value of blood urea nitrogen/creatinine (BUN/Cr) in predicting COPD with sarcopenia was evaluated using receiver operating characteristic (ROC) curve analysis. Additionally, a risk prediction nomogram model was constructed and validated. Results The study included a total of 128 patients, with 30 cases in the sarcopenia group and 98 cases in the non-sarcopenia group. The sarcopenia group had higher age, age-adjusted Charlson comorbidity index (ACCI), and BUN/Cr ratio than the non-sarcopenia group (P<0.05); body mass index (BMI), low-density lipoprotein cholesterol, albumin, prealbumin, Cr, 6-minute walk distance and forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) were lower in the sarcopenia group than those in the non-sarcopenia group (P<0.05). Multivariate logistic regression analysis showed that age, BMI, albumin, BUN/Cr and theFEV1/FVC were independent risk factors for sarcopenia in elderly COPD patients. ROC curve analysis was used to assess the predictive value of BUN/Cr for sarcopenia in the COPD patients, with an area under the ROC curve (AUC) of 0.725, an optimal cutoff point of 80.45, sensitivity of 60%, and specificity of 82.7%. A prediction model was constructed based on the above risk factors, with an AUC of 0.912 (95%CI 0.853-0.971), sensitivity of 80.0%, and specificity of 89.8%. The calibration curve of the prediction model fitted well. The decision curve analysis indicated that the nomogram had good clinical predictive performance within the threshold range of 0.2-0.8. Conclusion The BUN/Cr is associated with the development of sarcopenia in elderly COPD patients, and the predictive nomogram based on risk factors exhibits good performance for elderly COPD patients with concurrent sarcopenia.
