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Chronic obstructive pulmonary disease (COPD) is increasingly recognised as a systemic disease in which extrapulmonary comorbidities, including sarcopenia, osteoporosis and cardiovascular disease, contribute to symptoms, decreased functional capacity and mortality.1 As such, predicting functional decline in COPD using traditional lung function parameters alone can be difficult. 6-minute walk distance (6MWD) has emerged as a simple, validated measure of physical performance and an important prognostic tool in COPD.2 Notably, declines in 6MWD are more strongly associated with mortality than declines in forced expiratory volume in one second (FEV1),3 and 6MWD remains an independent predictor of survival after accounting for airflow limitation in COPD.4 Given the prognostic value of 6MWD, identifying patients with COPD at greatest risk for functional decline is crucial.