Active asthma and longer disease duration associated with more hyperinflation and increased diffusion capacity – TRAIL Cohort

Abstract

<b>Background:</b> Observations from long-term follow-up studies of well-characterised asthma in adults are sparse. We aimed to explore static lung volumes and diffusion capacity after over 30 years with asthma. <b>Methods:</b> A total of 125 adults with an objectively verified diagnosis of asthma between 1974-1990 at a Danish respiratory outpatient clinic, completed a follow-up visit 2017-19. All participants (age range 44-88 years) completed a comprehensive workup and were based on these assessments classified as having either active asthma or complete remission. The examination program included measurements of static lung volumes and diffusion capacity. <b>Results:</b> Participants with active asthma were hyperinflated (RV/TLC ratio 0.43, 95% CI 0.41—0.45) compared with those in remission (RV/TLC ratio 0.38, 95% CI 0.36—0.41). Participants with active asthma had a higher diffusion capacity (100 % predicted, 95% CI 97—104) compared to those in remission (94 % pred., 95% CI 89—99). Longer asthma duration was associated with higher diffusion capacity with 0.47 % (95% CI 0.14—0.80) higher per year, adjusted for age and smoking. Patients on GINA step 4 and 5 treatment were more hyperinflated (mean 14 % pred., 95% CI 3—27) and had higher airway resistance (mean 53% pred., 95% CI 9—97) compared with participants on GINA step 1. Persons with uncontrolled disease had substantially higher airway resistance (72% pred. 95% CI 20—124) than well-controlled individuals. <b>Conclusion:</b> Patients with active and severe asthma for more than 30 years have higher diffusion capacity and more hyperinflation compared to patients in remission.