Clinical characteristics and risk factors for frequent exacerbation in adult asthma patients

Abstract

Backgrounds and purpose: The purpose of the treatment of asthma includes adequate symptom control and prevention of acute exacerbation. Poorly controlled asthma can cause frequent acute exacerbations and leads to deterioration of quality of life, increase in healthcare cost, and mortality. In our study, we investigated the clinical characteristics of asthmatic patients who had frequent exacerbations and analyzed the risk factors that may affect frequent exacerbations.

Methods: We performed a multicenter cohort study, including four university-affiliated hospitals. And a frequent exacerbation was defined as at least two exacerbations, including unscheduled outpatient clinic visits, emergency room (ER) visits, or hospitalizations in one year. Severe exacerbation was defined as asthma exacerbation, which needs hospitalization or intensive care unit(ICU) care. This study consists of 2 parts: a retrospective case-control study based on medical record review and a later 1-year follow-up prospective cohort study. Patients who were diagnosed as asthma and treated for more than one year in each institution were recruited, and then their medical record was reviewed for filling out a pre-designed questionnaire. We discriminated against the patients with recurrent or severe acute exacerbations in the previous year from the whole study population. Clinical and demographic characteristics, laboratory results, pulmonary function tests, and medication history were collected to analyze the risk factors that may affect recurrent asthma exacerbation. Then the subjects were followed for another 1 year and analyzed the incidence and risk factors for the following exacerbations.

Results: A total of 240 patients were recruited, and 28 patients (11.7%) had a frequent exacerbation in the previous year. When comparing frequent exacerbation(FE +) group with no frequent exacerbation (FE -) group, FE+ group had lower ACT(Asthma control test) score at enrollment, and higher major depression history, lower predicted % of pre-bronchodilator FEV1. In the analysis of past asthma medications, the FE+ group used more short-acting beta-agonist(SABA) inhaler and oral corticosteroid(OCS) during the last 6 months than FE- group.

In the prospective cohort study for the following 1 year, 92 patients are lost to follow up. And from the remnant 148 patients, 22 patients (14.9%) had recurrent exacerbation during the following 1 year. When compared to FE- group, the FE+ group in the prospective study showed significantly lower ACT score at follow-up, and the other risk factors for asthma exacerbations did not show a significant difference. The patients from the FE+ group seemed to show higher frequent exacerbation in the following year than FE- group (52.9% vs. 9.9%), the statistical difference could not be assessed due to the high missing rate in both groups. With multiple logistic regression analysis, the total amount of OCS used (OR 1.03, 95% CI 1.001-1.005, p = 0.001) and ACT score at enrollment (OR 0.817, 95% CI 0.741-0.901, p <0.05) were statistically significant risk factors in the retrospective study. In the follow-up prospective study, total OCS amount (OR 1.005, 95% CI 1.002-1.008, p = 0.001) and ACT score at follow-up (OR 0.884, 95% CI 0.787-0.994, p = 0.039) also seemed to affect frequent exacerbation.

Conclusion: We investigated the clinical characteristics or possible risk factors for the frequent exacerbator by prospective cohort study. Frequent exacerbation in the previous year and poor asthma control status seemed to be significant risk factors for further recurrent exacerbation. The use of oral corticosteroids has also been shown to affect frequent exacerbations, but the causal relationship is unclear. Further research on other correctable risk factors for recurrent exacerbation and treatment is also needed with the more extensive, well-designed study.