Clinical features and determinants of COPD exacerbation in the Hokkaido COPD cohort study

Exacerbations are among the major factors that may affect the natural history of chronic obstructive pulmonary disease (COPD). The aim was to investigate the clinical characteristics and determinants of COPD exacerbations in our 5-year observational cohort study which had a very low exacerbation frequency. A total of 279 patients with COPD participated in the Hokkaido COPD cohort study, and 268 subjects who had clinical data for multiple visits were analysed. Exacerbation was defined in multiple ways: the patient's subjective complaint, symptom definition, requiring prescription change, requiring antibiotic treatment, or requiring hospital admission. Exacerbation frequency (events per person per year) was 0.78 +/- 1.16, 0.24 +/- 0.47, 0.20 +/- 0.43, 0.13 +/- 0.28 and 0.06 +/- 0.19 for subjective complaint and symptom, prescription, antibiotic and hospital admission definitions, respectively. Exacerbation events did not significantly affect the annual decline in forced expiratory volume in 1 s. A high St George's Respiratory Questionnaire total score, especially activity score, and a low body mass index were strongly associated with exacerbation-free survival, exacerbation frequency and development of recurrent exacerbations. Despite the low exacerbation frequency in our cohort, impaired health-related quality of life and weight loss were found to be independent risk factors for COPD exacerbations.