Purpose: Severe asthma is frequently accompanied by comorbidities such as chronic rhinosinusitis, nasal polyps, allergies, and gastroesophageal reflux disease (GERD). With increasing age, non-communicable conditions such as cardiovascular diseases and multimorbidity become more prevalent. This study aimed to analyze the prevalence of comorbidities and their impact on asthma-related outcomes over a two-year period using data from the Swiss Severe Asthma Registry (SSAR).

Patients and methods: We included 234 patients with baseline data and 2 years of follow-up visits from the SSAR. Patient's asthma control (ACT), quality of life (QoL), forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), diffusing capacity of the lungs for carbon monoxide (DLCO) and fraction expiratory nitric oxide (FeNO) and their association to comorbidities were analyzed longitudinally using general estimation equations (GEEs) with log link function.

Results: Over the study period, ACT and QoL scores significantly improved, and the frequency of exacerbations declined. The prevalence of the examined comorbidities remained stable. However, the presence of chronic obstructive pulmonary disease (COPD) was significantly associated with lower ACT scores, reduced QoL, and impaired pulmonary function (all p < 0.05). GERD was also linked to lower ACT and QoL (p < 0.05), while depression was associated with a significant decrease in DLCO (p < 0.05).

Conclusion: Our findings underscore the strong impact of comorbidities-particularly COPD, GERD, and depression-on asthma control, quality of life, and lung function in patients with severe asthma. These results highlight the need for integrated, multidisciplinary management strategies targeting comorbid conditions to improve overall asthma outcomes. Further research should explore these subgroups in more detail to guide personalized treatment approaches.