Other measures

It was expected that, when participants are asked to walk and perform the concurrent cognitive task, they would differ in the weighting they gave to walking or task performance. For example, stroke participants have been noted to adopt a strategy of altering the grammatical content of speech and adopting a slower gait speed during dual-task in order to maintain performance in both tasks (Pohl et al 2011). In contrast, when stroke participants were required to cross obstacles whilst walking and performing a cognitive task (Smulders et al 2012) results suggested that maintaining gait was prioritised. Yogev-Seligmann et al (2012) have proposed a model that explains the integration of factors such as the individual’s cognitive state, compensatory capabilities and personality that may be involved in task prioritisation. The study design therefore included collection of other measures that were chosen to describe the participants and to allow investigation of whether observed changes in gait and/or cognitive task could be explained by factors other than the presence or absence of FES. The following discusses the measures chosen.

a) Falls measures

One possible explanation for participants’ choice of priorities could have been their falls history, and perceived risk and attitudes about the safety of walking and the possibility of falling. Advice was sought from the lead clinician of the local NHS falls service (Greene 2008) in the choice of measures appropriate to capture these potentially influential factors.

A widely used validated tool, at the time of designing this study, was the Falls Efficacy Scale (FES) (Appendix B.4) (Tinetti et al., 1990). This scale was designed to measure self-perceived fear of falling (Hellstrom and Lindmark, 1999) by assessing confidence in performing ten activities of daily living without falling (Yardley et al.,

2005) on a scale of one (most confident) to ten (least confident). A score out of 100 was obtained when the scale was applied, with higher scores indicating lower confidence. The scale had been used in several stroke studies (Michael et al., 2006, Fritz et al., 2007, Michael et al., 2009). Participants completed the scale at baseline and both subsequent data collection visits to examine change in confidence over time with use of their FES device and subsequent relationship to primary outcome measures.

As recommended in a study exploring fear of falling (Delbaere et al., 2010a) this measure of perceived falls risk was matched by a measure of falls risk based on external factors. A large variety of measures are cited in the research literature to assess this risk. To reduce the burden of the study on participants a quick and simple tool was chosen that was used locally in Salford by the falls team (Greene, 2008) and was designed for use in primary care. The Falls Risk Assessment Tool (FRAT) (Nandy et al., 2004) has five items (Appendix B.5). Three or more risk factors positively predict a fall within the next six months. Again, this was collected at baseline and both subsequent data collection visits, in particular to note any change in risk with time.

Finally, the participant’s fall history was recorded, to match perceived risk with actual risk in this instance, via discussing fall or near fall events, using a proforma to record details of each event (Lord et al., 2007)(Appendix B.6). At the initial visit participants were asked to recall events during the previous 12 months, whilst at subsequent data collections they were asked to recall any events during the intervening period. Whilst one of the highly rated reasons for use of FES, by users, is a reduction in the risk of falling and tripping (Section 2.4.3e) only one study to date has assessed the effect of FES on the occurrence of falls (Hausdorff and Ring, 2008) noting a decrease in incidence. Results from the data from this study will potentially add to knowledge in this area.

b) Cognitive abilities

The participants were also assessed in terms of their general cognitive abilities as this would influence their performance on a cognitive task whilst walking. Thus outcomes of a cognitive assessment could be used in analysis of primary results to explain the contribution of this variable to the outcomes. The opinions of two

psychologists experienced in the field of stroke rehabilitation and research (Bowen 2007 and 2008, Kitching 2008) were sought to establish the most appropriate tests to quantify and describe this factor. Two tests were chosen to quantify this factor, both of which are well established in the field of neuropsychological assessment, and are relatively brief, in keeping with minimising the burden of the study on the participant. Both tests were applied once at the beginning of data collection.

Firstly, to estimate the participants’ pre-morbid (i.e. pre-stroke) state of mental ability the National Adult Reading Test (NART) (Nelson, 1991) was used. This test is often used to estimate this ability in adults as vocabulary correlates best with overall ability level (Lezak et al., 2004). The NART is comprised of fifty words printed in order of increasing difficulty (Appendix B.7). The words are ‘irregular’ and thus can only be read correctly if the participant recognises them, rather than phonetically decode the word if it is unfamiliar. The test requires the participant to read aloud the list of words. The number of errors made are recorded and this is used to obtain an estimation of their predicted pre-morbid general intellectual ability (Bright et al., 2002). The score is converted to Predicted WAIS-R Full Scale IQ using the conversion scale devised by Nelson and Willison (Nelson, 1991) following re-standardisation of the NART.

Secondly, the Digit Span test from the Wechsler Memory Test (Wechsler, 1981) was used to assess the participants’ level of attention (forward span) and working memory (backwards span) (Lezak et al., 2004). A series of increasingly longer digit sequences are spoken by the researcher, and the participant is requested to repeat each sequence exactly. In the case of the backwards span, the participant is required to repeat them in an exactly reversed order (Appendix B.8). For both forwards and backwards spans, the participant repeats increasingly longer series until they are no longer able to do so correctly, and each span is scored out of 14. The raw unconverted scores for both forward and backwards spans can be evaluated against a scale indicating the range of performance abilities (Lezak et al., 2004). Scores of 6 and above for the forward test are within normal limits, and scores of 4 and above are within normal limits for the latter (Lezak et al., 2004).

c) Overall independence

An overall measure of daily functioning was determined at each data collection visit to describe the cohort and to identify any changes that may have occurred over time.

The Barthel Index (Mahoney and Barthel, 1965) was used to provide an overall measure of independence in activities of daily living (ADL) (Loewen and Anderson, 1990)(Appendix B.9). This is a well-established and widely used (van der Putten et al., 1999) global measure of functional status (Loewen and Anderson, 1990) that has been included in the ‘Stroke: Transfer of Care Summary’ produced by the Royal College of Physicians (RCP, 2008b).

d) Sensory neuropathy

Finally, participants were assessed for peripheral neuropathy of the feet and lower legs, using a 10 gram monofilament to apply a standardised assessment (NICE, 2004). Neuropathy can affect balance when walking and contributes to a greater risk of falls (Richardson et al., 1992, DeMott et al., 2007) and hence may influence task prioritisation. As with other measures in this study, neuropathy was assessed at each data collection to assess any changes over the duration of the study.