Changes in the BODE index, exacerbation duration and hospitalisation in a cohort of COPD patients

INTRODUCTION: We investigated the relationship between frequency of exacerbation and duration and change in functional status, as measured by the BODE index in chronic obstructive pulmonary disease (COPD) patients. METHODS: This was a longitudinal cohort study of 56 patients with moderate to severe COPD. Body mass index, spirometry, Modified Medical Research Council (MMRC) dyspnoea score and six-minute walk distance (6MWD) were measured annually when the patients were clinically stable. Data on frequency and duration of COPD exacerbations occurring in the community and requiring hospitalisation were collected prospectively. Early stage exacerbations were identified through the use of individualised patient action plans and further reinforced by fortnightly phone contact. RESULTS: At the two-year follow-up, the BODE index increased in 33 patients, remained stable in 18 and decreased in five patients. Patients with increased BODE index had significantly higher hospital presentation rates and longer total bed-days compared to those with stable BODE index. Among the 33 patients with increased BODE index, 20 had lower 6MWD and higher MMRC scores, indicating deteriorating functional status, and 13 had higher levels of airway obstruction. Between these two subgroups, patients with deteriorating functional status had higher exacerbation frequency, longer exacerbation duration and higher inpatient bed-days. Linear regression showed that total annual duration of exacerbation was predictive of change in 6MWD. CONCLUSION: Change in the BODE index is a sensitive measure of deteriorating functional status in COPD patients. Duration of exacerbation has greater impact on functional status than frequency of exacerbation episodes.