Health-related quality of life and associated factors among adults with bronchial asthma assessed by the EQ-5D-5L: an unmatched case–control study in southern Vietnam

Background and Objectives Evidence on health-related quality of life (HRQoL) measured with EQ-5D-5L and its determinants in Vietnamese adults with asthma is limited. We estimated the proportion of patients with HRQoL impairment (EQ-5D-5L index <1), described affected dimensions, and identified independent correlates. Methods We conducted an unmatched case–control study (case:control = 1:2) at a district-level Asthma–COPD outpatient clinic in Ho Chi Minh City between October 2024 and March 2025. Adults with physician-confirmed asthma per GINA 2023 were consecutively enrolled. Cases were defined as patients with EQ-5D-5L index <1; controls had index=1. Both groups were identified from the same source population and enrolled concurrently. The Vietnamese EQ-5D-5L value set was applied. Univariable and multivariable logistic regression yielded crude and adjusted odds ratios (aOR) with 95% confidence intervals (CI). Reporting followed STROBE. Results Of 210 patients (median age 58 years; 68.6% female), 39 (18.6%) were cases. Anxiety/depression was the most affected dimension (11.9%), followed by mobility (10.0%). Median EQ-5D-5L index was 1.0000 (IQR 1.0000–1.0000), with a ceiling effect of 81.4%; median EQ-VAS was 80 (IQR 70–85). No missing data were identified for any key variable. In multivariable analysis, older age (aOR 1.90 per 1 SD ≈16.3 years; 95% CI 1.08–3.33; p=0.026) and female sex (aOR 2.72; 95% CI 1.00–7.36; p=0.049) were independently associated with impairment, while higher FEV 1 was protective (aOR 0.58 per 1 SD ≈20.3% increase; 95% CI 0.39–0.87; p=0.008). Model fit: Hosmer–Lemeshow p=0.374; Nagelkerke R 2 =0.236; AUC=0.773. EQ-5D-5L index and EQ-VAS did not differ across GINA control categories (Kruskal–Wallis p=0.791 and p=0.214). Conclusions Nearly one in five outpatients had HRQoL impairment, predominantly in the anxiety/depression dimension. Older age, female sex, and reduced lung function were independently associated with impairment. HRQoL screening should be integrated into asthma care with special attention to mental health in older women and patients with reduced FEV 1 .