Prevalence, disease burden, and treatment reality of patients with severe, uncontrolled asthma in Japan

The severe asthma and severe, uncontrolled asthma (SUA) populations in Japan are not well-studied. We investigated the prevalence of continuously treated severe asthma and SUA patients, their disease burden, and the treatment reality via a Japanese health insurance claims database.

Continuously treated asthma patients (patients prescribed inhaled corticosteroids for asthma ≥4 times in the past year) aged ≥17 years at the index date (latest visit between April 2014 and March 2015 for asthma treatment) were included in this analysis (KEIFU study, UMIN000027695). Asthma severity and control status at the index date were defined using modified criteria of ERS/ATS guidelines. Asthma hospitalization, oral corticosteroid (OCS) use, and total medical expenses were calculated using data up to 12 months post-index date.

We identified 10,579 patients as continuously treated asthma patients. Of these, 823 (7.8%) had severe asthma; 267 (2.5%) and 556 (5.3%) patients had SUA and severe, controlled asthma (SCA), respectively. Compared with SCA and mild to moderate asthma patients, a greater percentage of SUA patients required hospitalization (13.7%, 6.2%, and 3.0%, respectively) and were prescribed OCSs (67.4%, 45.9%, and 16.2%, respectively). Yearly total medical expenses were also greater for SUA patients (mean [standard deviation]: 8346 [12,280], vs 5989 [10,483] and 3422 [8800] USD, respectively).

The percentages of severe asthma and SUA patients continuously treated in Japan were obtained through this large-scale analysis using a health insurance claims database. SUA patients had greater medical and economic burdens, suggesting more appropriate treatment is required according to the treatment guidelines.