The relationship between asthma duration and FEV1 among distinct severe asthma phenotypes

<bold>Background:</bold> The influence of variable disease duration in severe asthma (SA), and its phenotypes, is unknown. <bold>Aims:</bold> We investigated the relationship between asthma duration and lung function according to SA phenotypes in U-BIOPRED. <bold>Methods:</bold> We included SA patients aged ≥18 at baseline. Long and short duration of asthma was defined as ≥15 or <15 years, respectively. Patients were stratified by sputum proteomic clusters.¹ Wilcoxon rank sum and Chi-squared tests with Bonferroni correction were used for comparisons. Links between asthma duration and FEV1 were determined using multivariable linear regression models adjusted for age, sex, BMI, ethnicity and smoking history. <bold>Results:</bold> In 411 SA patients, 137 (33%) and 274 (67%) had a short (median[IQR]: 8[5-12] years) and long (32[23-43] years) duration of asthma, respectively. Previous ICU admission (31vs9%, p<0.001), pneumonia (44vs27%, p=0.047) and lower FEV1% (63vs73%, p=0.032) were more likely in patients with asthma for ≥15 years compared with <15 years. Asthma duration was independently associated with FEV1 (−6mL, 95%CI-10,-2). In 131 SA patients with well-characterised granulocyte and atopic phenotypes, longer asthma duration was associated with lower FEV1 in eosinophilic asthma (−16mL, 95%CI -31,-1) [Table 1]. <bold>Conclusion:</bold> Longer disease duration may be important in patients with severe eosinophilic asthma, likely to be due to differences in pathobiological mechanisms. <fig><object-id>erj;64/suppl_68/PA1247/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>