Change in gait speed predicts hospitalization, death in IPF patients

A considerable decline of >0.07 m/s in 4-metre gait speed (4MGS) over 6 months is associated with a higher risk of all-cause, nonelective hospitalization or death over the next 6 months in patients with a newly diagnosed idiopathic pulmonary fibrosis (IPF), suggests a study.

“4MGS change has potential as a surrogate endpoint for interventions aimed at modifying hospitalization/death,” the researchers said.

The mean change in 4MGS over 6 months was ‒0.05 m/s (95 percent confidence interval [CI], ‒0.09 to ‒0.01; p=0.02). A decline of 0.07 m/s or more in 4MGS over 6 months demonstrated better discrimination for the index event than change in 6-minute walk distance, forced vital capacity, Composite Physiologic Index, or Gender Age Physiology index. [Respirology 2023;28:649-658]

A significant between-group difference in time to event was observed in Kaplan‒Meier curves (substantial decline vs minor decline/improvers: >‒0.07 vs ≤‒0.07 m/s; p=0.007). Those with substantial decline were at greater risk of hospitalization/death (adjusted hazard ratio, 4.61, 95 percent CI, 1.23‒15.83). A multiple imputation analysis revealed similar results.

“We observed a decline in 4MGS over 6 months in IPF that was comparable to the decline observed in patients with chronic obstructive pulmonary disease (COPD) over 12 months, consistent with different disease trajectories and more rapid functional decline in IPF compared to COPD,” the researchers said. [Eur Respir J 2014;43:1298-1305]

“This decline correlated with [decrease] in established exercise capacity, increased respiratory disability, and deterioration in health-related quality of life measures,” they added.

Consistent results

Previous studies that explored the relationship between change in gait speed and prognosis focused on community-dwelling older adults. Results were consistent in showing either a reduced mortality risk with improving gait speed or higher mortality with a reduction in gait speed. [J Gerontol A Biol Sci Med Sci 2013;69:354-362; J Gerontol A Biol Sci Med Sci 2012;68:456-464; Hepatology 2016;63:574-580]

On the other hand, data on the association between change in gait speed and hospitalization were limited. One such study reported fewer inpatient hospitalization days for each annual 0.10-m/s increase in gait speed among older veterans. [J Rehabil Res Dev 2005;42:535-546]

“Further research is required to corroborate [the current] findings, but we propose that 4MGS may have potential as a surrogate endpoint of adverse outcomes in people with IPF,” the researchers said.

Some 132 individuals with newly diagnosed IPF and measured 4MGS change over 6 months participated in this prospective cohort study. The composite outcome events were first hospitalization and death at 6 months. Eighty-five participants had complete data (paired 4MGS plus index event). To address the missing data, multiple imputation was used.

The researchers used receiver-operating curve plots to identify a 4MGS change cut-point. They also used Cox proportional hazard regression to examine the association between 4MGS change and time to event.

“IPF is characterized by a progressive functional decline and poor prognosis,” the researchers said. “There is interest in validating surrogate endpoints that are associated with adverse outcomes, such as hospitalization or death, since these could potentially reduce the sample size, duration, and costs of clinical trials.” [Am J Respir Crit Care Med 2011;183:788-824; Thorax 2012;67:938-940]