Age-Stratified Analysis of the Clinical Efficacy of Subcutaneous Immunotherapy for Allergic Rhinitis in Chinese Patients

<b>Background/Objectives:</b> To investigate the relationship between patient age and the clinical efficacy of subcutaneous immunotherapy (SCIT) for allergic rhinitis (AR), aiming to provide a reference for patient selection and efficacy improvement in clinical practice. <b>Methods:</b> We conducted a retrospective statistical analysis of clinical data from 240 AR patients who underwent standardized house dust mite (HDM) SCIT for at least 6 months at our hospital between 2019 and 2025. Patients were stratified into four age groups (children, young adults, middle-aged adults, and the elderly) according to the World Health Organization (WHO) classification. The clinical efficacy, nasal symptom scores, Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) scores, peripheral blood regulatory T cell (Treg) and regulatory B cell (Breg) levels, and adverse reactions were analyzed across these age strata. Additionally, to investigate the underlying mechanisms, we utilized a public single-cell transcriptomic dataset (GSE176269; <i>n</i> = 35, age 4 months-65 years) to assess the relationship between T cell senescence and age through data integration and senescence gene set scoring. For multiple comparisons, the significance level was adjusted using the Bonferroni method. This adjustment ensured the overall significance level (α) of the study was maintained at 0.05, and the final adjusted significance level (α') for each age group was 0.0125. <b>Results:</b> The overall response rate for the entire cohort was 62.5%. Age-stratified analysis revealed a significantly higher response rate in children (83.3%) compared to middle-aged and elderly patients (48.5% and 20%, respectively), with the difference being statistically significant (<i>p</i> < 0.001). Following treatment, both total nasal symptom scores and RQLQ scores decreased significantly across all age groups compared to baseline (<i>p</i> < 0.001). Peripheral blood Treg and Breg levels increased post-treatment in all age groups; however, the increase was not statistically significant in the middle-aged and elderly groups (<i>p</i> > 0.0125). The incidence of systemic adverse reactions was 4.17% (all Grade I), occurring primarily in the child and young adult groups, but the difference among age groups was not statistically significant (<i>p</i> > 0.0125). Mechanistically, our single-cell analysis revealed that T cells within the nasal mucosa exhibit significant age-dependent senescence. <b>Conclusions:</b> SCIT is a safe and effective treatment for AR across all age groups. However, pediatric patients appear to derive greater benefit compared to middle-aged and elderly patients, a finding that corresponds with age-stratified immunological data. Therefore, different efficacy expectations should be considered when selecting SCIT for patients of varying ages, and future research should explore strategies targeting T cell senescence to enhance desensitization efficacy in elderly patients.