Relationship Between Asthma Control Status and Health-Related Quality of Life in Japan: A Cross-Sectional Mixed-Methods Study.

INTRODUCTION:There is limited information regarding multidimensional relationships between asthma control and health-related quality of life (HRQoL), work productivity, and asthma symptom burden in Japan. Furthermore, systematic qualitative investigations about asthma burden have not been performed. METHODS:This cross-sectional, mixed-methods study included Japanese patients (≥ 20 years) with asthma adherent to inhaled corticosteroids/long-acting β2-agonists (ICS/LABA). The primary endpoint was impact of asthma on HRQoL, measured using the Asthma Health Questionnaire-33 (AHQ-33). Secondary endpoints were cough burden (Japanese-adapted Leicester Cough Questionnaire [J-LCQ]) and impact of asthma on work/activities (asthma-specific Work Productivity and Activity Impairment Questionnaire [WPAI:Asthma]). Quantitative data were assessed for the overall population and for well-controlled (WC) and not well-controlled (NWC) asthma subgroups. Qualitative verbal interviews further assessed the impact of NWC asthma on patients' HRQoL; emergent themes were extracted using thematic analyses. RESULTS:Of 454 patients, 45.2% (n = 205) had NWC asthma. Patients with NWC asthma had significantly worse asthma- and cough-related HRQoL across all AHQ-33 and J-LCQ domains and significantly greater work and activity impairment versus patients with WC asthma, across all assessed WPAI:Asthma domains. AHQ-33 total score was highly correlated with J-LCQ total and domain scores (r = - 0.8132 to r = - 0.7407). Nine themes emerged from qualitative interviews and confirmed that patients with NWC asthma had considerable HRQoL impairment due to asthma symptoms. CONCLUSIONS:Patients with NWC asthma had higher symptom burden and worse HRQoL than patients with WC asthma, despite ICS/LABA adherence. Cough burden correlated with HRQoL, suggesting cough may be one of the key markers to inform treatment strategy for patients with asthma.