Real-world walking cadence in people with COPD

Abstract

Introduction: The clinical validity of real-world walking cadence in people with COPD is unsettled. Our objective was to assess the levels, variability and association with clinically relevant COPD characteristics and outcomes of real-world walking cadence.

Methods: We assessed walking cadence (steps per minute during walking bouts longer than 10 s) from 7 days' accelerometer data in 593 individuals with COPD from five European countries, and clinical and functional characteristics from validated questionnaires and standardised tests. Severe exacerbations during a 12-month follow-up were recorded from patient reports and medical registries.

Results: Participants were mostly male (80%) and had mean±sd age of 68±8 years, post-bronchodilator forced expiratory volume in 1 s (FEV₁) of 57±19% predicted and walked 6880±3926 steps·day^-1. Mean walking cadence was 88±9 steps·min^-1, followed a normal distribution and was highly stable within-person (intraclass correlation coefficient 0.92, 95% CI 0.90-0.93). After adjusting for age, sex, height and number of walking bouts in fractional polynomial or linear regressions, walking cadence was positively associated with FEV_1, 6-min walk distance, physical activity (steps·day^-1, time in moderate-to-vigorous physical activity, vector magnitude units, walking time, intensity during locomotion), physical activity experience and health-related quality of life and negatively associated with breathlessness and depression (all p<0.05). These associations remained after further adjustment for daily steps. In negative binomial regression adjusted for multiple confounders, walking cadence related to lower number of severe exacerbations during follow-up (incidence rate ratio 0.94 per step·min^-1, 95% CI 0.91-0.99, p=0.009).

Conclusions: Higher real-world walking cadence is associated with better COPD status and lower severe exacerbations risk, which makes it attractive as a future prognostic marker and clinical outcome.

FIGURE 1

Real-world walking cadence in 593 individuals with COPD. Min: minimum; P₂₅: 25th percentile; Med: median; P₇₅: 75th percentile; Max: maximum.

FIGURE 2

Unadjusted and adjusted associations between clinical measures of COPD and real-world walking cadence, with p-values reported from linear regressions or fractional polynomial regressions. FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; mMRC: modified Medical Research Council scale; HRQoL: health-related quality of life; CAT: COPD Assessment Test; CCQ: Clinical COPD Questionnaire; HADS-D/A: Hospital Anxiety and Depression scale – Depression/Anxiety; MVPA: moderate-to-vigorous physical activity; VMU: vector magnitude units; C-PPAC: Clinical visit – PROactive Physical Activity in COPD; na: not applicable. ^#: unadjusted p-value; ^¶: p-value adjusted for age, sex, height and number of walking bouts; ⁺: p-value adjusted for age, sex, height, number of walking bouts and steps.