Four trajectories of severe asthma have been identified that have different patterns of progression but similar disease burden and morbidity.

An observational study based on Swedish data from the NORdic Dataset for aSThmA Research (NORDSTAR) [link here] tracked 4,543 severe asthma patients over a ten-year period.  

During each year of follow-up, patients were classified according to asthma severity based on their asthma treatment level for that calendar year. The research team also looked at the time to severe asthma, minimum asthma treatment level, and the number of changes in the progression of treatment levels.

The analysis revealed four ‘clinically meaningful’ trajectories of severe asthma: “consistently severe asthma” (n=389, 8.6%),  “gradual onset severe asthma” (n= 942, 20.7%), “intermittent severe asthma” (n=1685, 37.1%), and “sudden onset severe asthma” (n=1527, 33.6 %).

All four trajectories had a high burden of disease with only a few clinically relevant differences in asthma medication use, asthma control outcomes and co-morbidities, the researchers reported in their paper published in the European Respiratory Journal. 

“From a clinical point of view, we believe this finding is intuitive and highlights that once severe asthma has occurred the morbidity of disease is critical regardless of different ways of developing severe asthma,” the authors wrote. 

For example, those with “consistently severe asthma” had a higher daily inhaled corticosteroid dose and more prevalent osteoporosis compared with the other trajectories.

Whereas patients with “sudden onset severe asthma” were less likely to have allergy, rhinitis, atopic dermatitis, osteoporosis and cardiovascular disease compared to the “consistently severe asthma” trajectory. 

Differences were also seen in clinical events preceding disease progression in patients with new onset severe asthma. 

Patients with “gradual onset severe asthma” had higher markers of uncontrolled asthma, respiratory infections and T2- related co-morbidities ten years prior to developing severe asthma compared to patients with “sudden onset severe asthma”, who had lower levels until one to three years before developing severe asthma. 

“Clinically, we believe that these two trajectories suggest that for both “gradual onset severe asthma” and “sudden onset severe asthma”, the period of increasing loss of asthma control prior to developing severe asthma, seems to be concomitant with an increase in T2-comorbidities,” the investigators wrote. 

This finding suggested that patients with a combination of increasing loss of asthma control and development of T2 co-morbidities were an at-risk group for severe asthma development, and a possible group to target for earlier interventions.  

“Once severe asthma is developed the morbidity of disease appears to be similar irrespective of trajectory to disease. This emphasises the need for early identification of patients at high risk of progressing into severe asthma as well as the importance of future development of early interventions to prevent asthma progressing into severe disease,” the study authors concluded.  

The trial was financially supported by Novartis and Sanofi & Regeneron Pharmaceuticals.