Losing control and developing concerns : The complexities of ageing postural control and fall-related concerns
Abstract: With the world population shifting its proportions towards higher ages, it is imperative to increase healthspan rather than lifespan, both for the sakes of community sustainability as well as individual quality of life. One of the main means to obtain healthy ageing, is a concept called active ageing, as activity has shown to slow down the natural ageing process. Active ageing is threatened by a decline in balance performance and an increase of fall-related concerns, as activity curtailment is a major consequence. Fall-related concerns are prevalent in a large portion of the older population. Current understanding of its mechanisms is largely hypothesised, based on few observational studies in which single factors – mostly psychological – are researched. Postural control is the system that helps us maintain balance and control while moving or being still. Yet, the interactions between fall-related concerns and postural control are not very well described. Sensory input and processing have been identified as possibly an important part, but more in-depth investigations are needed.To investigate the prevalence and factors that may play a part in fall-related concerns, 153 older adults (70 years and over) were visited in their home. During these visits questionnaires and clinical tests were administered (among them FES-I, PGCM, SPPB, MMSE). To investigate the relationship between fall-related concerns and postural control more thoroughly, 45 of the original sample were also tested in the movement laboratory. Several modalities of sensory function were recorded, as well as lower limb strength and quiet stance centre of pressure. The home visits showed that 70% of people 70 years and older, living in the community experience at least one of the constructs of fall-related concerns and that associated factors are of both psychological and physical nature (fear, morale, and physical performance). Large and significant differences between men and women were discovered not only in prevalence, but also for the associated factors. Hierarchical multivariate modelling of the laboratory data showed that an increase in sway size and velocity during open eyes quiet stance can explain a rise in fall-related concerns and that that relationship in turn can be explained by declines in specific parts of the postural control system (lower limb strength, reaction time, vision, and proprioception of the ankle, knee, and neck). The more in-depth methods of frequency domain and multivariate discriminant analysis revealed that older participants could be grouped in ‘declined and concerned’ and ‘not declined and not concerned.’ The first showing power in lower frequencies of the postural sway signal than the latter and showing an inability to adjust control strategy when closing their eyes. Finally, the changing and adapting postural control of older people was successfully modelled by applying dimension reduction, neural networks, and an internal feedback of 150ms. The model can predict postural corrections up to 1 second ahead of time. This gave more insight in key features of successful adaptation to an ageing system and provides a virtual environment for future model and theory testing. In conclusion, I have gained more understanding of the complexity and interaction of the different systems involved in the concern-and-balance relationship and have contributed to the field by showing methods that will improve the quality of analyses when testing, evaluating, and researching these phenomena.
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