Elderly Patients with Tuberculosis Combined with Diabetes Mellitus: A Comprehensive Analysis of Lymphocyte Subpopulation Dynamics, Clinical Features, Drug Resistance and Disease Regression

Objective: The aim of this study was to evaluate lymphocyte subsets and clinical outcomes in patients with pulmonary tuberculosis (PTB) combined with type 2 diabetes mellitus (T2DM). Methods: Between January 2022 and March 2024, 320 patients aged > 60 years were included, 95 of whom had comorbid DM. Lymphocyte subsets (T-lymphocytes, B-lymphocytes, and natural killer cells, NK) were assessed in both groups of patients using fluorescence-associated cell sorting. Clinical characteristics, drug resistance, regression and lymphocyte subsets were compared in PTB patients with DM versus PTB patients alone. The correlation between lymphocyte subsets-related indices and the above characteristics in PTB patients with DM was analyzed. Results: Compared with PTB patients alone, PTB patients with comorbid DM had a higher positive rate (81.05% vs 62.67%, P = 0.001), prolonged course of antituberculosis treatment (298 [244, 339] days vs 223 [179, 254], P < 0.001) and a lower cured rate (64.21% vs 75.56%, P = 0.039). Compared with PTB patients only, PTB patients with comorbid DM had higher T-lymphocytes and CD4+ T-lymphocytes (P < 0.001, P = 0.006) and lower NK cells (P < 0.001). In PTB patients with comorbid DM, both treatmentprolonged patients and drug-resistant patients showed reduced NK cells. NK cells were slightly elevated in cured patients, although there was no significant difference (P = 0.082). Conclusion: Lymphocyte homeostasis is altered in PTB patients with comorbid DM, making them more susceptible to severe clinical manifestations and therapeutic outcomes. Notably, NK cells have been identified as key regulatory cells with a significant impact on prolonged treatment course and drug resistance. This study provides new ideas and methods for individualized treatment of PTB combined with DM in the elderly, which can help to optimize the treatment plan and improve the outcome and quality of life of patients.