目的·探讨儿童重症支气管哮喘（简称哮喘）的流行病学特征并分析其危险因素。方法·采用单中心前瞻性队列研究，纳入2021年1月1日—12月31日就诊于复旦大学附属儿科医院的难治性哮喘患儿674例，建立动态队列。收集队列成员的基本信息（包括患儿性别、年龄、出生胎龄、出生体质量等）和共存疾病情况，评估其哮喘控制情况、药物吸入技术水平、药物依从性，以及肺功能指标［1秒用力呼气容积（forced expiratory volume in one second，FEV₁）占预计值百分比（FEV₁%预计值），FEV₁/用力肺活量（forced vital capacity，FVC）和用力呼出50%肺活量的呼气流量（forced expiratory flow at 50% of FVC exhaled，FEF₅₀）、FEF₇₅、FEF_25-75占预计值百分比］、气道炎症指标［呼出气一氧化氮（fraction exhaled nitric oxide，FeNO）检测值］和过敏状态指标［外周血嗜酸性粒细胞（eosinophil，EOS）计数和总血清免疫球蛋白E（immunoglobulin E，IgE）浓度］。所有队列成员分别在其进入队列的第3、6、9和12个月至该院哮喘专病门诊接受再次评估。结果·至队列终点时，有52例（7.7%）患儿被诊断为重症哮喘。处于二手烟暴露环境、家中常年使用空调、共存疾病为鼻炎/鼻窦炎、FEV₁%预计值<80%、FEV₁/FVC<80%、小气道功能障碍、EOS>300/μL、IgE>200国际单位（international unit，IU）/L、FeNO>20/25 ppb［FeNO>20 ppb（≤12岁），>25 ppb（>12岁），1 ppb=1×10^-9 mol/L］在重症哮喘患儿中占比较高，母乳喂养至6月龄及以上、药物依从性好在非重症患儿中占比较高，差异有统计学意义（均P<0.05）。6~11岁重症哮喘患儿中男性占比更多，12~17岁重症哮喘患儿中女性占比更多，差异有统计学意义（均P<0.05）。多因素Logistic回归分析显示，小气道功能障碍是发生重症哮喘的独立危险因素［OR=5.158（95%CI 2.516~10.572）］。结论·难治性哮喘患儿在规范管理1年后，重症哮喘患儿占比有显著下降趋势；小气道功能障碍是其进展为重症哮喘的独立危险因素。

Objective ·To explore the epidemiological characteristics of severe asthma in children and analyze the risk factors. Methods ·A single-center prospective cohort study was conducted. Six hundred and seventy four children with difficult-to-treat asthma who visited the Children′s Hospital of Fudan University from January 1 to December 31, 2021 were included to establish a dynamic cohort. Basic information (including gender, age, gestational age at birth, birth weight, etc.) and comorbidity of the cohort members were collected. The asthma control status, drug inhalation technique level, medication compliance, pulmonary function parameters [forced expiratory volume in one second (FEV₁) as a percent-age of the predicted value (FEV₁%pred), FEV₁/ forced vital capacity (FVC), and the rate of estimated values of forced expiratory flow at 50% of FVC exhaled (FEF₅₀), FEF₇₅, and FEF_25-75 in percent-predicted value, respectively], airway inflammation index [fraction exhaled nitric oxide (FeNO)], and allergy status parameters [eosinophil (EOS) and immunoglobulin E (IgE)] of all cohort members were evaluated. All cohort members underwent re-evaluation respectively at the specialist asthma clinic of the hospital at 3, 6, 9, and 12 months. Results ·At the endpoint of the cohort, 52 children were diagnosed with severe asthma, accounting for 7.7%. A high proportion of severe asthma was found in children who were exposed to secondhand smoke, used air conditioning at home all year round, or had coexisting rhinitis/nasosinusitis, FEV₁%pred<80%, FEV₁/FVC<80%, small airway dysfunction, EOS>300/μL, IgE>200 IU/L, or FeNO>20/25 ppb [FeNO>20 ppb (≤12 years old) or >25 ppb (>12 years old), 1 ppb=1×10^-9 mol/L]. A high proportion of non-severe asthma was found in children who were breastfed for 6 months or longer, or had good medication compliance. The differences were statistically significant (all P<0.05). There were more males in children with severe asthma aged 6?11 years, and more females in children with severe asthma aged 12?17 years, with statistical significance (both P<0.05). Multiple-factor Logistic regression analysis showed that only small airway dysfunction was an independent risk factor for severe asthma [OR=5.158 (95%CI 2.516?10.572)]. Conclusion ·The proportion of children with severe asthma has a significantly decrease after one year of standardized management in children with difficult-to-treat asthma. Small airway dysfunction is an independent risk factor for the progression to severe asthma.