Abstract
<title>Abstract</title> <p>Background This study analyzed the demographic characteristics, smoking history, pulmonary function, fractional exhaled nitric oxide (FeNO), complete blood count, total IgE, and other relevant indicators of outpatients in a hospital in Shanxi Province during the periods of July to September from 2022 to 2024. It aimed to explore the characteristics and duration of changes in airway sensitivity before and after the widespread COVID-19 pandemic in China, and to elucidate the patterns and potential mechanisms underlying the impact of SARS-CoV-2 infection on airway sensitivity. Methods A retrospective cross-sectional analysis recruited 500 respiratory outpatients annually from a Shanxi hospital each July–September across 2022 (pre-pandemic), 2023 and 2024 (1 and 2 years post mass infection), with 1500 subjects in total. We gathered demographic, smoking, pulmonary function, exhaled nitric oxide, blood routine and serum total IgE data. Chi-square test handled categorical data, while one-way ANOVA plus LSD post-hoc tests assessed normally distributed continuous indicators. Results Age and smoking rate showed a “decrease then rebound” trend (2022: 50.04 years, 38.4%; 2023: 47.19 years, 29.8%; 2024: 50.86 years, 37.4%). The positive rate of airway hyperresponsiveness was 20.8% in 2022, peaked at 26.8% in 2023, and declined to 21.2% in 2024 (P = 0.039). The FEV₁ decline after provocation was 7.93% in 2022, sharply rose to 12.59% in 2023, and partially recovered to 10.18% in 2024 (P < 0.001). Eosinophil counts (×10⁹/L) and total IgE (IU/mL) increased from 0.14 and 142.79 in 2022 to 0.23 and 191.59 in 2023, then decreased to 0.20 and 163.95 in 2024, both remaining above baseline (all P < 0.001). FeNO₅₀ showed no significant difference across the three years (P > 0.05). Conclusions After SARS‑CoV‑2 infection, airway sensitivity and type 2 inflammatory markers exhibited a pattern of “sharp rise in 2023, partial remission in 2024 but still above baseline,” indicating that infection independently drives increased respiratory sensitivity, with partially reversible but long‑term systemic immune dysregulation. The dissociation between FeNO and systemic markers suggests a predominantly systemic immune imbalance. In the post‑pandemic era, infection history should be incorporated into respiratory health risk assessments, and long‑term management should be strengthened. Trial registration No tial registration.</p>