Relationships between falls risk, gait speed, and head-trunk control in people with Parkinson's disease and elderly.

BACKGROUND: Impaired head and trunk control in people with Parkinson's disease (PwPD) is expected to impede upper body stabilization during walking and increase the risk of falls. This study assessed the relationships between falls risk, gait speed, and head-trunk control in PwPD and healthy elderly. METHODS: Twenty-five older PwPD and 25 healthy elderly walked at their preferred and fast walking speeds. A 20-ft-introduction walkway measured gait speed and triaxial accelerometers on lower trunk and head segments assessed upper body motion. The root mean square of acceleration was calculated to indicate segment control. Falls risk was determined using the Physiological Profile Assessment. FINDINGS: Accelerations of the trunk and vertical head were strongly positively related to preferred speed for both groups. For fast speed, these associations were weaker. PwPD group had significantly greater falls risk and walked slower than healthy elderly. PwPD group with greater falls risk walked slower for preferred and fast speeds, while healthy elderly at greater falls risk walked slower for only the fast condition. After removing the influence of gait speed, some accelerations were significantly associated with falls risk in the healthy elderly. INTERPRETATION: Walking speed largely drives sagittal plane trunk and VT head accelerations in PwPD and healthy elderly. While ML trunk and transverse plane head accelerations are largely dependent on individual differences in postural control. Falls risk manifests differently in self-selected speed and trunk and head accelerations in PwPD and healthy elderly.