Differences in axial segment reorientation during standing turns predict multiple falls in older adults

Abstract

Background

The assessment of standing turning performance is proposed to predict fall risk in older adults. This study investigated differences in segmental coordination during a 360° standing turn task between older community-dwelling fallers and non-fallers.

Methods

Thirty-five older adults age mean (SD) of 71 (5.4) years performed 360° standing turns. Head, trunk and pelvis position relative to the laboratory and each other were recorded using a Vicon motion analysis system. Fall incidence was monitored by monthly questionnaire over the following 12 months and used to identify non-faller, single faller and multiple faller groups.

Results

Multiple fallers were found to have significantly different values, when compared to non-fallers, for pelvis onset (p = 0.002); mean angular separation in the transverse plane between the head and trunk (p = 0.018); peak angular separation in the transverse plane between the trunk and pelvis (p = 0.013); and mean angular separation between the trunk and pelvis (p < 0.001).

Conclusions

Older adults who subsequently experience multiple falls show a simplified turning pattern to assist in balance control. This may be a predictor for those at increased risk of falling.

Introduction

Falls and fall-related injuries are amongst the most serious and common medical problems experienced by the older population with approximately one-quarter of community-dwelling people aged 65 and over reporting at least one fall in a year [1]. Turning is one of the fundamental components of mobility, and is associated with 35–45% of steps in common everyday tasks [2]. Staggering when turning is a prominent characteristic of recurrent fallers [3], and those who are unsteady during turning are more likely to fall whilst turning [4]. If an individual does experience a fall during turning, they are eight times more likely to fracture their hip than if the fall occurred when walking in a straight line [5]. These findings suggest that turning could be a greater challenge to older people at risk of falling than walking straight ahead, and result in more serious consequences.

Assessment of standing turn performance is considered of value in predicting potential fall risk in older adults [6], and as a result has been included in many clinical tests. The 360° turn forms part of regularly used clinical assessment tools for assessing dynamic balance in older persons [7], [8], [9], with a longer turn time and a greater number of steps associated with an increased risk of falling [10] and loss of independence in activities of daily living [11]. Performance on the 360° turn is also strongly associated with walking speed and chair rise ability [12]. Therefore, the 360° turn is a useful measure of function in older adults.

During a turn, there is a clear temporal sequence in the initiation of axial segment reorientation. The movement is initiated in the yaw direction by the head, followed by the trunk and finally the feet in a cranio–caudal sequence [13]. Older adults have demonstrated less head on trunk rotation than young adults during a 130° turning task [14], which was suggested to be due to age-related decreases in cervical spine rotation. This reduced head on trunk rotation was partly compensated by increased trunk on pelvis rotation. However this is in contrast to a study of a 90° standing turn, which found that older adults started turning their head, trunk and pelvis simultaneously [15]. This en-bloc method of segmental reorientation may be adopted to simplify the control of the movement and to minimalise the risk of imbalance. This en-bloc strategy has also been demonstrated in patients groups such as turning in place in Parkinson's Disease [16] and online steering in stroke [17]. This en-bloc strategy may therefore be demonstrated in older adults who are at risk of experiencing a fall, and the 360° turn that is already utilised in clinical balance assessments may be suitable for identifying differences that may be present prior to falling.

Anticipatory postural adjustments (APAs) occur prior to a voluntary movement and have been observed in scenarios such as lateral stepping [18] and gait initiation [19]. In lateral stepping, the centre of pressure (COP) showed a small shift towards the swing side prior to the weight transfer to the support side [18]. This COP adjustment preceded a centre of mass (COM) adjustment. Longer APA time has been reported during obstructed gait initiation in older adults at high risk of falling compared to those at low risk, suggesting that those adults need a longer preparatory control time [19]. Therefore, it is likely that APAs will be detectable in standing turning.

Therefore, the purpose of this study was to investigate prospectively any differences in segmental coordination and APAs during a 360° standing turn task between older community-dwelling fallers and non-fallers. It was hypothesised that the fallers would display less segment-to-segment rotation during the turn, and demonstrate a longer APA time than the non-fallers.