Factors Associated with Domain-Specific Asthma-Related Quality of Life in Adults with Asthma

Background/Objective: Asthma-related quality of life is related to multiple clinical, physiological, and behavioral factors. Nonetheless, the domain-specific associations of asthma control, inhaler adherence, lung function, and demographic characteristics remain poorly understood. This study aimed to examine the adjusted associations of asthma control, inhaler adherence, lung function, and age with individual domains of asthma-related quality of life. Methods: This cross-sectional observational study included 92 adults with asthma who demonstrated correct inhaler technique and adequate knowledge of their prescribed inhaler regimen. Asthma control was measured using the Asthma Control Test (ACT), inhaler adherence using the Test of Adherence to Inhalers (TAI), and quality of life using the Asthma Quality of Life Questionnaire (AQLQ). Pulmonary function was determined through spirometry. Spearman correlation analyses were initially conducted to identify associations between variables. Subsequently, separate multivariable linear regression models were created for each AQLQ domain, including ACT score, TAI score, age, and FEV1 % predicted as predictors. Results: A total of 92 adult patients with asthma were studied. Asthma control was significantly positively correlated with all AQLQ domains (all p < 0.001). In multivariable analyses, ACT had the largest absolute standardized coefficient within each of the four domain-specific models (standardized β range: 0.339–0.791). After adjustment, age was associated with the activity limitation and symptom domains, whereas FEV1 % predicted was associated only with the environmental stimuli domain. Inhaler adherence showed an inverse association with emotional functioning in the fully adjusted model (B = −0.094, 95% CI −0.158–−0.031; p = 0.0038). However, this association was absent in the bivariate analysis and in a sensitivity model excluding ACT (B = −0.015, 95% CI −0.067–0.037; p = 0.562), suggesting a possible suppression effect. Conclusions: ACT showed the largest standardized association within each domain-specific model, although the magnitude of its associations with the symptom and activity-limitation domains may partly reflect conceptual overlap between the instruments. The inverse TAI–emotional-functioning coefficient was model-dependent, did not meet the conservative multiplicity benchmark, and should be considered exploratory and hypothesis-generating. Additionally, lung function and age showed domain-specific associations, highlighting the need for a comprehensive, multidimensional approach in asthma management.