Background: Patients with COPD might not report mild exacerbation. The frequency, risk factors, and impact of mild exacerbation on COPD status are unknown. Objectives: The present study was performed to compare features between mild exacerbation and moderate or severe exacerbation in Japanese patients with COPD. Patients and methods: An observational COPD cohort was designed at Keio University and affiliated hospitals to prospectively investigate the management of COPD comorbidities. This study analyzes data only from patients with COPD who had completed annual examinations and questionnaires over a period of 2 years (n=311). Results: Among 59 patients with mild exacerbations during the first year, 32.2% also experienced only mild exacerbations in the second year. Among 60 patients with moderate or severe exacerbations during the first year, 40% also had the same severity of exacerbation during the second year. Findings of the COPD assessment test and the symptom component of the St George’s Respiratory Questionnaire at steady state were worse in patients with mild exacerbations than in those who were exacerbation free during the 2-year study period, although the severity of the ratio of predicted forced expiratory volume in 1 second did not differ between them. Severe airflow limitation (the ratio of predicted forced expiratory volume in 1 second <50%) and experience of mild exacerbations independently advanced the likelihood of an elevated COPD assessment test score to ≥2 per year. Conclusion: The severity of COPD exacerbation seemed to be temporally stable over 2 years, and even mild exacerbations adversely impacted the health-related quality of life of patients with COPD.
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