Falls and injuries related to falls constitute a large problem in the United States with 25-30% of adults over the age of 65 yrs falling annually. Of these, greater than 50% occurred during walking or some type of locomotion. The purposes of this study were to characterize the relationship between postural control and gait variability in older adults with and without a falls history, and to explore how executive function affects both postural control and gait variability as it relates to falling. Methods: Cross sectional design. Subjects: Participants included community dwelling older adults aged 65 to 85 yrs who were able to walk a minimum of 5 min without an assistive device. Measurements: Stride time variability was recorded using pressure-sensitive foot switches during usual and dual task walking. Postural control was measured with the Sensory Organization Test (SOT) and Limits of Stability Test (LOS) using the NeuroCom Smart Balance System. Clinical measures included the Dynamic Gait Index (DGI) and Activities Specific Balance Confidence Scale (ABC). Executive function measures included the Clock Drawing Test and the Trial Making Tests (TMT) part A and B. Known risk factors for falls were identified from the literature and calculated for each subject. Results: All postural control measures, ABC, DGI and Trial Making Test A and B were able to differeniate non-fallers and fallers, with fallers scoring worse in all testing. Stride time variability was consistent between groups during both walking conditions. The SOT composite score was inversely related to stride time variability under both conditions for fallers only. The DGI was the strongest in predicting stride time variability during usual and dual task conditions. The DGI cut score of 19.5 had a sensitivity of 68% and specificity of 72% in differentiating fallers from non-fallers. DGI < 19.5 combined with TMT B>74 s enhanced the ability to identify individuals not at risk for falls, but results in more false positives. Odds ratios (OR) for falling were: TMT B>74 s=4.1; DGI <19.5=5.4;8 or more risk factors =7.3; and combined TMT B>74 s and DGI< 19.5 =17.8. However, if 8 risk factors and TMT <74 s were present the OR was 0.2. Clinical relevance: Falls are multifactorial: it is important to not only identify impairments, but to also identify problems with postural control strategies. Psturography, specifically the SOT and LOS-MXE, is a valuable tool to identify fallers and to specify the type of postuyral control problem. The DGI appears to be an essential tool in the identification of those at risk of falling especially during gait activities, and should be considered part of the standard of care when examining older adults with risk for falls. Executive function, specifically flexibility of thought, appears to be used in the management of postural instability and related impairments. As demonstrated in this study, the slowing of cognitive flexibility substantially increases the odds of falling. Therefore, clinical use of the TMT test may enhance the discrimination power of postural control measures. Clinicians need to consider interventions aimed at remediating neuromuscular impairments, as well as those designed to enhance cognitive flexibility to better manage the impairments that persist.
