The prevalence and disease burden of severe eosinophilic asthma in Japan

Abstract

Background: There are limited data on the prevalence and burden of severe eosinophilic asthma (SEA) both in Japan and globally. This study aimed to assess the prevalence and burden of SEA in Japan. Methods: This study was a retrospective, observational cohort analysis using health records or health insurance claims from patients with severe asthma treated at Kyoto University Hospital. The primary outcome was the prevalence of SEA, defined as a baseline blood eosinophil count !300 cells/lL. Secondary outcomes included frequency and risk factors of asthma exacerbations, and asthma-related healthcare resource utilization and costs. Results: Overall, 217 patients with severe asthma were included; 160 (74%) had eosinophil assessments. Of these, 97cases (61%), 54cases (34%), and 33cases (21%) had a blood eosinophil count !150, !300, and !500 cells/lL, respectively. Proportion of SEA was 34%. Blood eosinophil count was not associated with a significantly increased frequency of exacerbations. In the eosinophilic group, lower % forced expiratory volume in 1 second and higher fractional exhaled nitric oxide were predictive risk factors, while the existence of exacerbation history was a predictive risk factor for asthma exacerbations in the non-eosinophilic group. Severe asthma management cost was estimated as ¥357,958/patient-year, and asthma exacerbations as ¥26,124/patient-year. Conclusions: Approximately, one-third of patients with severe asthma in Japan have SEA. While risk factors for exacerbations differed between SEA and severe noneosinophilic asthma, both subgroups were associated with substantial disease and economic burden. From subgroup analysis, blood eosinophil counts could be an important consideration in severe asthma management.

The Prevalence, Characteristics, and Patient Burden of Severe Asthma Determined by Using a Japan Health Care Claims Database

“…17,18 In several studies, including TENOR (Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens), patients experiencing a recent exacerbation were 6-to 8-fold more likely to experience a future exacerbation than those without a recent exacerbation. 13,19,20 Consistent with this finding, the present study's multivariate analysis showed that the risk of exacerbations during the follow-up period increased in patients who currently had severe asthma or eosinophilic disease or who had experienced asthma exacerbations in the previous year. Among patients with severe asthma, the risk of a subsequent exacerbation increased in patients who experienced an exacerbation in the previous year and in patients who used daily oral corticosteroids for 3 months.…”

“…8e11 A cross-sectional survey conducted in northern California found that the total per-person costs for severe asthma are almost triple those for moderate asthma. 9 In Japan, although several studies 12,13 have been conducted to assess severe asthma subphenotypes in patients treated in a hospital-based setting, the clinical characteristics, disease burden, and patient behavior have not been well documented for severe asthma treated in various clinical settings, including local hospitals and clinics.…”

Burden of Asthma in Elderly Japanese Patients: Using Hospital-Based Administrative Claims Data

“…We also found that for Japanese patients with severe asthma, asthma-associated total outpatient costs and hospitalization costs (per patient) increased with age. The total outpatient cost associated with severe asthma (¥319,436/patient/year) was similar to that previously reported by Nagasaki et al (¥357,958/patient/year) [14]. Since Nagasaki et al [14] estimated medical costs between 2013 and 2014 using claims data in Kyoto University Hospital, the characteristics of the study population might have been similar to those in our study.…”

“…The total outpatient cost associated with severe asthma (¥319,436/patient/year) was similar to that previously reported by Nagasaki et al (¥357,958/patient/year) [14]. Since Nagasaki et al [14] estimated medical costs between 2013 and 2014 using claims data in Kyoto University Hospital, the characteristics of the study population might have been similar to those in our study. However, another retrospective cohort study conducted by Inoue et al reported the total outpatient cost (comprising ER visits, outpatient visits, and prescriptions) of ¥141,515/patient/year between 2009 and 2015; this discrepancy may be due to the study period.…”

Blood eosinophil count as predictor of asthma exacerbation. A meta‐analysis

“…Sixteen cohort studies, [10][11][12][13][14][15][16]18,19,21,28,[36][37][38][39][40] 6 cross-sectional studies, 7,8,20,25,41,42 and one case-control study 17 examined the association of elevated blood eosinophil count with asthma exacerbation.…”