Gait speed and mortality in chronic obstructive pulmonary disease (COPD)

Introduction: Functional and exercise capacity measures provide additional prognostic information in COPD, but many are not feasible at point of care testing. 4 metre gait speed(4MGS) is a simple physical performance measure that is consistently associated with adverse events in older adults. Method: In 371 patients with COPD attending hospital outpatient clinics, 4MGS, Medical Research Council(MRC) dyspnoea score, body mass index(BMI) and FEV1 were measured. The Age Dyspnoea Obstruction(ADO) index, an established prognostic index, was also calculated. Survival status was collected at 3 years. Cox proportional hazard regression was performed with censoring at 3 years. Receiver Operating Characteristic curves were plotted and compared to FEV1 %predicted and ADO. The model was validated in an independent cohort of 472 patients attending community COPD clinics. Results: Baseline characteristics: (mean(SD)): age 70(10), 58% male, BMI 27.8(6.6), MRC 3(1), FEV1 48.6(20.1)%pred, 4MGS 0.89(0.24) m/s. 4MGS was feasible in all participants. A multivariate model of 4MGS, Age, FEV1 and Sex(GAFS) was predictive of mortality at 3 years, with better discrimination than ADO and FEV1 and an area under the curve(AUC) of 0.74. In the validation cohort, the AUC of GAFS was 0.70. Conclusion: Gait speed is feasible as a point of care functional test in outpatient/community settings, and provides additional prognostic information in COPD than ADO or FEV1 alone.