Role of Gait Speed in the Assessment of Older Patients
Authors: Matteo Cesari
Journal: JAMA (2011)

OVER THE LAST 3 DECADES, A LARGE AND increasing amount of evidence has documented the importance of physical function in elderly individuals, both as a crucial component of clinical assessment as well as a specific outcome for interventions. However, the evaluation of physical function is still not considered as relevant as that of other clinical or biochemical parameters. Insufficient time, inadequate space, and the need for special equipment are some of the obstacles to the routine assessment of physical function in the geriatric clinical settings. To overcome these limitations, gait speed has repeatedly and increasingly been proposed as an unique measure of physical performance and as a potential screening tool, but adoption has remained inconsistent. In this issue of JAMA, the study by Studenski et al fills an important research gap and paves the way to a broader adoption of gait speed assessment. Their findings from a pooled analysis of 9 major cohort studies confirm gait speed as a predictor of mortality in older persons and also provide the statistical foundations to estimate expected survival at different ages based only on gait speed. Several barriers limiting the clinical use of physical performance measures might thus be considered overcome. First, the study establishes the validity of a test readily adoptable to clinical use that, differently from other functional assessment tools, is inexpensive, objective, and easy to interpret. Second, the study standardizes the methods to assess gait speed to the 4-meter-long track starting from a still, standing position. This is not a trivial accomplishment because gait speed has often been measured testing individuals over tracks of different lengths (eg, 8 ft or 4 or 6 m), sometimes after exclusion of the initial acceleration time, leading to difficulties in interpretation, comparability, or both. Third, the study by Studenski et al assesses survival of older persons associated with various gait speed results. The increase in life expectancy at a population level has further highlighted the heterogeneity of individuals, making it increasingly difficult to distinguish merely old (chronologically aged) from geriatric (biologically aged) patients. This very ability to screen frail geriatric patients vs old individuals is an urgent matter in geriatrics but increasingly urgent in other specialties. For example, oncologists seek objective methods to identify patients eligible for standard and more aggressive interventions because they are chronologically, but not biologically, old. Also, cardiac surgeons have proposed gait speed as a means to identify which older patients undergoing surgery may be at increased risk for adverse outcomes. Assessment of gait speed may serve as a single-item screening tool to determine which patients need a geriatric multidisciplinary approach to care. At the same time, gait speed should be regarded as an important component of the comprehensive geriatric assessment, provided it facilitates clinical decisions on the basis of a “hard” outcome such as life expectancy. The study by Studenski et al may also be of interest for investigators involved in clinical research on aging. Researchers and clinicians seek results that are clinically, not just statistically, significant. Because of the established association of gait speed with survival, it could be used as a surrogate for survival outcomes in clinical trials of older persons. Gait speed should not be regarded solely as a measure of lower extremity function. Gait speed has been associated with clinical (eg, comorbidities) as well as subclinical conditions (eg, atherosclerosis or inflammatory status) and is able to predict several health-related events even apparently unrelated to physical function (eg, cognitive impairment, hospitalization, institutionalization). Gait speed may serve as a marker of physiological reserve and potentially could quantify overall health status. Indeed, a close relationship between mobility performance and the aging process has been documented in humans and animals. This convergence may indicate the existence of shared pathophysiological mechanisms; thus, at some point, gait speed may be considered a new “vital sign,” specifically sensitive for older persons. Results by Studenski et al showed that gait speed had only a statistically fair accuracy for predicting survival for gait speed (pooled area under the receiver operator char-