Activity: Professional Development, Mentorship, Supervision and Other Activities › External HDR Supervision
Measuring Physical Function in People with Dementia: A psychometric investigation
Dementia is a global issue, and it is a growing problem. Exercise is an effectiveintervention strategy for improving cognition and physical function for people of allages, and measurement is fundamental to scientific endeavour. This thesis sits atthe crossroads to these three key areas. Without appropriate psychometricjustification behind the choice of measurement tools for exercise intervention studies,the validity of outcomes to suggest that exercise is beneficial for people withdementia should be called into question. This thesis aims to identify commonmeasures of physical function, a key construct to remaining independent for peoplewith dementia, assess their psychometric properties and determine whether suchmeasures are suitable for use for people with dementia. This thesis uses a multistage, mixed methods approach, with each stage founded upon its own question toanswer. Stage One answers the question; what measures of physical function arecurrently used in exercise intervention studies? Stage Two answers the question;have common measures been rigorously assessed for their psychometric propertiesin a dementia specific population? Stage Three answers the question; are commonmeasures, previously unassessed, valid and reliable in a sample of people withdementia? Stage Four answers the question; what does it mean for a person withdementia to be ‘physically able’?In Stage One, the systematic review of the benefits of exercise for people withdementia demonstrated significant heterogeneity, making a meta-analysis and finalrecommendation on the frequency, intensity and time of exercise for this populationdifficult. A significant factor in this was the large number of outcome measureschosen to demonstrate the benefits of exercise. Sub-group analysis with identical iiimeasures was able to demonstrate homogeneity. Part of the findings from thisreview was that physical function as a construct is poorly defined and measured. InStage Two, a second systematic review was undertaken. This examined thepsychometric properties of all measures from Stage One in dementia specificpopulations. While some measures had garnered the attention of researchers, manymeasures had no, or very little psychometric investigation. This potentiallyundermines the validity of the intervention studies reviewed in Stage One. In StageThree, a subset of commonly used measures of physical function, which had notpreviously been assessed, were subject to a seven day test-retest reliability trial andvideo analysis of the standardised protocol. The majority of measures had highlevels of relative reliability (ICC > 0.71), but low levels of absolute reliability, asdemonstrated by large Standard Error of Measures and Limits of Agreement. Theprevalence of error in task execution and non-standardised instruction wassignificantly different in the first trial (p<0.05), generally these differences were nolonger present by the third trial (p>0.05). It was evident that the majority of oursample were able to complete the measures to standardised the protocol. In StageFour, the previous definitions of physical function, which centre on capacity tocomplete complex and basic daily tasks, is appropriate for people with dementia.However, further attention should be given to the tasks most basic and central toremaining independent.The discussion focussed on three main findings from this thesis. These are; there isreasonable evidence to support the use of assessed measures, intended use shouldguide clinicians and researchers, and simple measures for people that have lowphysical and low cognitive function should be used. Implications will translate thesemain findings into expected consequences of this work. A Rasch Analysis of the ivdata from Stage Three was briefly presented to demonstrate the applicability of thisapproach to future psychometric investigation into this area.