What are the relations between voluntary postural sway measures and falls-history status in community-dwelling older adults?

OBJECTIVES To determine whether a series of voluntary postural sway tasks could differentiate and accurately identify the falls-history status of older adults, and to examine the relations between voluntary sway measures and falls risk. DESIGN Case-control study. SETTING University biomechanics laboratory. PARTICIPANTS Healthy community-dwelling older adults (N=51) aged 65 to 94 years who were divided into nonfaller (n=36), single faller (n=10), and multiple faller (n=5) groups based on a 12-month history of falls. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Participants underwent a falls-risk assessment using the Physiological Profile Assessment (PPA) and then performed 6 voluntary postural sway tasks. The tasks included maximum static leans, maximum voluntary sway, continuous voluntary sway, rapid initiation of voluntary sway, rapid termination of voluntary sway, and rapid orthogonal switches of voluntary sway between the anterior-posterior and medial-lateral directions. Center of pressure amplitudes and reaction time measures were examined using analysis of covariance, Pearson's correlation, and discriminant function analyses. RESULTS Multiple fallers had increased age; increased falls risk; slower initiation, termination, and orthogonal switch reaction times; and reduced center of pressure amplitude during sway initiation and continuous voluntary sway compared with nonfallers. Few differences were observed between the nonfallers and single fallers. Voluntary sway measures were significantly correlated with each other and with PPA score. Two postural reaction time measures and age identified 80% of multiple fallers and 98% of nonmultiple fallers. Similarly, PPA score and age identified 80% of multiple fallers and 100% of nonmultiple fallers. CONCLUSIONS The slower and less effective balance responses of multiple fallers compared with nonfallers and the comparable sensitivity and specificity of PPA score and reactive voluntary sway measures indicate that postural reaction time is a strong determinant of falls risk.