Step length and fall risk in adults with chronic kidney disease: a pilot study

BACKGROUND: Patients with chronic kidney disease commonly experience gait abnormalities, which predispose to falls and fall-related injuries. An unmet need is the development of improved methods for detecting patients at high risk of these complications, using tools that are feasible to implement in nephrology practice. Our prior work suggested step length could be such a marker. Here we explored the use of step length as a marker of gait impairment and fall risk in adults with chronic kidney disease. METHODS: We performed gait assessments in 2 prospective studies of 82 patients with stage 4 and 5 chronic kidney disease (n = 33) or end-stage renal disease (ESRD) (n = 49). Gait speed and step length were evaluated during the 4-m walk component of the Short Physical Performance Battery (SPPB). Falls within 6 months prior to or following enrollment were identified by questionnaire. Associations of low step length (≤47.2 cm) and slow gait speed (≤0.8 m/s) with falls were examined using logistic regression models adjusted for demographics and diabetes and peripheral vascular disease status. RESULTS: Assessments of step length were highly reproducible (r = 0.88, p < 0.001 for duplicate measurements at the same visit; r = 0.78, p < 0.001 between baseline and 3-month evaluations). Patients with low step length had poorer physical function, including lower SPPB scores, slower gait speed, and lower handgrip strength. Although step length and gait speed were highly correlated (r = 0.73, p < 0.001), one-third (n = 14/43) of patients with low step length did not have slow gait speed. Low step length and slow gait speed were each independently associated with the likelihood of falls (odds ratio (OR) 3.90 (95% confidence interval (CI) 1.05–14.60) and OR 4.25 (95% CI 1.24–14.58), respectively). Compared with patients who exhibited neither deficit, those with both had a 6.55 (95% CI 1.40–30.71) times higher likelihood of falls, and the number of deficits was associated with a graded association with falls (p trend = 0.02). Effect estimates were similar after further adjustment for ESRD status. CONCLUSIONS: Step length and gait speed may contribute additively to the assessment of fall risk in a general adult nephrology population.