Background The economic impact of multimorbidity in severe or difficult-to-treat asthma has not been comprehensively investigated. Aims To estimate the incremental healthcare costs of coexisting chronic conditions (comorbidities) in patients with severe asthma, compared with non-severe asthma and no asthma. Methods Using health administrative data in British Columbia, Canada (1996–2016), we identified, based on the intensity of drug use and occurrence of exacerbations, individuals who experienced severe asthma in an incident year. We also constructed matched cohorts of individuals without an asthma diagnosis and those who had mild/dormant or moderate asthma (non-severe asthma) throughout their follow-up. Health service use records during follow-up were categorised into 16 major disease categories based on the International Classification of Diseases. Incremental costs (in 2016 Canadian Dollars, CAD$1=US$0.75=₤0.56=€0.68) were estimated as the adjusted difference in healthcare costs between individuals with severe asthma compared with those with non-severe asthma and non-asthma. Results Relative to no asthma, incremental costs of severe asthma were $2779 per person-year (95% CI 2514 to 3045), with 54% ($1508) being attributed to comorbidities. Relative to non-severe asthma, severe asthma was associated with incremental costs of $1922 per person-year (95% CI 1670 to 2174), with 52% ($1003) being attributed to comorbidities. In both cases, the most costly comorbidity was respiratory conditions other than asthma ($468 (17%) and $451 (23%), respectively). Conclusions Comorbidities accounted for more than half of the incremental medical costs in patients with severe asthma. This highlights the importance of considering the burden of multimorbidity in evidence-informed decision making for patients with severe asthma.

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重度哮喘患者多发病的经济负担：一项为期 20 年的人群研究

背景 尚未对重度或难治性哮喘中多发病的经济影响进行全面调查。目的 与非重度哮喘和无哮喘患者相比，估计重度哮喘患者共存慢性病（合并症）的增量医疗保健成本。方法 使用加拿大不列颠哥伦比亚省（1996-2016 年）的卫生行政数据，我们根据药物使用强度和急性发作的发生率确定了在事件发生年份中经历过严重哮喘的个体。我们还构建了未诊断为哮喘的个体和在整个随访期间患有轻度/休眠或中度哮喘（非重度哮喘）的个体的匹配队列。根据国际疾病分类，随访期间的卫生服务使用记录被分为 16 个主要疾病类别。增量成本（以 2016 年加元计算，1 加元=0.75 美元=₤0.56=0.68 欧元）估计为重度哮喘患者与非重度哮喘和非哮喘患者之间的医疗保健成本调整差异。结果 相对于无哮喘，重度哮喘的增量成本为每人年 2779 美元（95% CI 2514 至 3045），其中 54%（1508 美元）归因于合并症。相对于非重度哮喘，重度哮喘与每人每年 1922 美元的增量成本相关（95% CI 1670 至 2174），其中 52%（1003 美元）归因于合并症。在这两种情况下，最昂贵的合并症是哮喘以外的呼吸系统疾病（468 美元（17%）和 451 美元（23%），分别）。结论 合并症占重症哮喘患者增量医疗费用的一半以上。这凸显了在对严重哮喘患者进行循证决策时考虑多种疾病负担的重要性。