BackgroundInvestigation for the presence of asthma comorbidities is recommended by GINA as their presence can complicate asthma management.ObjectiveTo understand the prevalence and pattern of comorbidities and multimorbidity in adults with severe asthma and their association with asthma-related outcomes.MethodsThis was a cross-sectional study using data from the International Severe Asthma Registry from 22 countries. Thirty comorbidities were identified and categorized a priori as either (1) potentially T2-related, (2) potentially oral corticosteroid (OCS)-related or (3) mimicking/aggravating asthma. The association between comorbidities and asthma-related outcomes was investigated using multivariable models adjusted for country, age at enrollment, and sex.ResultsOf 11,821 patients, 69%, 67%, and 55% had ≥1 potentially T2-related, potentially OCS-related, or mimicking/aggravating comorbidities, respectively; 57% had ≥3 comorbidities, and 33% had comorbidities in all three categories. Patients with allergic rhinitis (AR), nasal polyposis (NP), and chronic rhinosinusitis (CRS) experienced 1.12- (p=0.003), 1.16- (p<0.001) and 1.29-times (p<0.001) more exacerbations/year, respectively, than those without. Patients with NP and CRS were 40% and 46% more likely (p<0.001), respectively, to have received long-term (LT) OCS. All assessed potential OCS-related comorbidities (except obesity) were associated with greater likelihood of LTOCS use (ORs: 1.23-2.77) and, except for dyslipidemia, with greater likelihood of uncontrolled asthma (ORs: 1.29-1.68). All mimicking/aggravating comorbidities assessed were associated with more exacerbations (1.24-1.68 times more), all (except bronchiectasis) with increased likelihood of uncontrolled asthma (ORs: 1.57-1.81) and all (except COPD) with increased likelihood of LTOCS use (ORs: 1.37-1.57). Greater number of comorbidities was associated with worse outcome.ConclusionIn a global study, comorbidity or multimorbidity is reported in most adults with severe asthma and is associated with poorer asthma-related outcomes.