Impact of symptom variability on clinical outcomes in COPD: analysis of a longitudinal cohort

Abstract

Purpose

We compared clinical characteristics of COPD patients according to symptom variability and evaluated the effect of symptom variability during the first year of enrollment on clinical outcomes of COPD.

Methods

We analyzed COPD patients’ data from the Korean Obstructive Lung Disease (KOLD) cohort. Symptom variability was defined based on the value of standard deviation (SD) of mMRC scores obtained every 3 months during the follow-up period of the first year. Patients were divided into 2 groups: the consistent (SD of mMRC scores =0) and variable (SD of mMRC scores >0) groups. Clinical characteristics and outcomes were compared in terms of symptom variability.

Results

A total of 407 patients were included in the analysis. Patient age was 67.2 years and 97.8% of the subjects were male. Initial mMRC was 1.5 and the SD of mMRC scores during the first year was 0.5. There were 137 subjects (33.7%) in the consistent group and 270 (66.3%) in the variable group. The variable group showed a lower FEV₁ (P=0.019) and a higher mMRC score (P=0.001). The annual incidence of acute exacerbation of COPD (AE-COPD) tended to be higher in the variable group (P=0.078) and that of severe AE-COPD was higher in the variable group than in the consistent group (P=0.002). The variable group showed a higher proportion of annual exacerbators (P=0.001) and frequent exacerbators (P=0.017). In multivariate logistic regression analysis, the variable group was significantly associated with annual exacerbators (OR =1.963, P=0.011) and frequent exacerbators (OR =2.090, P=0.055).

Conclusion

COPD patients with symptom variability may have higher exacerbation risk as well as lower lung function and more severe respiratory symptoms.

Keywords:

• COPD
• symptom
• variability
• exacerbation
• death
• lung function

Supplementary materials

Figure S1 Survival function curves of time to the first exacerbation according to symptom variability. Time to the first exacerbation was shorter in the variable group than in the consistent group, for symptom variability during the follow-up period (P=0.056)

Figure S2 Survival function curves according to symptom variability. There was no significant difference in survival rates between the variable and consistent groups

Disclosure

The authors report no conflicts of interest in this work.