Does the occurrence of a severe asthma exacerbation change the rate of subsequent events?

Background Severe exacerbations requiring hospitalization are an important component of the natural history of asthma and a major source of its burden. Whether the occurrence of a severe exacerbation affects the rate of subsequent events has far-reaching implications in asthma management. Methods Using the centralized administrative health databases of British Columbia, Canada (1997/01/01 –2016/03/31), we created an incidence cohort of patients with at least one severe asthma exacerbation, defined as an episode of hospitalization with asthma as the primary diagnosis. We used an accelerated failure time joint frailty model for the time intervals between severe asthma exacerbations. Analyses were conducted separately for pediatric (< 14 years old) and adult (≥14 years old) patients. Results There were 3,039 patients (mean age at baseline 6.4, 35% female) in the pediatric group and 5,459 patients (mean age at baseline 50.8, 68% female) in the adult group, with 16% and 15%, respectively, experiencing at least one severe asthma exacerbation during follow-up. The first follow-up severe asthma exacerbation was associated with an increase of 79% (95% CI: 15% – 186%) in the rate of the subsequent events for the pediatric group. The corresponding value was 186% (95% CI: 85% – 355%) for the adult group. For both groups, the effects of subsequent severe exacerbations were not statistically significant. Conclusion Our findings suggest that among patients who have experienced their first severe asthma exacerbation, preventing the next event can drastically change the course of the disease and reduce the burden of future exacerbations.