Resultados

Despite the predictive value of PM for detecting MCI, above and beyond that of RM (Blanco-Campal, Coen, Lawlor, Walsh and Burke, 2009), none of the screening tools recommended by the Alzheimer’s Association and ICGP contain a test for PM. Indeed, few recommendations for fuller objective assessment of memory include a validated assessment of this aspect of memory. This appears to be an important oversight given the evidence showing that PM failures make an independent contribution to the prediction of AD over and above that of RM failures (Jones, Livner & Backman, 2006).

As noted in Chapter 1, PM failures are common in the general population (Dobbs & Rule, 1987). Inclusion within the primary care setting of an assessment of this type of memory, given its potentially serious personal consequences, is, therefore, potentially important. Although such a test needs to be brief enough for use in a primary care setting, based on findings in numerous research studies, an interesting consideration for potential use in clinical practice (perhaps in an abbreviated format) is the Cambridge Prospective Memory Test (CAMPROMPT) described next.

The CAMPROMPT is one of just two commercially available standardised objective assessment of complex prospective memory (PM). This 25 minute test is comprised of three time-based and event-based (one focal and two non-focal) items embedded within a series of attention-demanding puzzles that serve as an ongoing task, e.g. “when there are seven minutes left, remind me not to forget my keys” and “when you come to a quiz question about (television show), give me this book.” Participants are allowed to engage

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in any external strategies they like to help them remember, including taking notes, and are provided with a pen and paper.

The CAMPROPMPT has a very high inter-rater reliability of 0.998 (Pearson) and moderate test-retest reliability of 0.64 (Kendell’s Tau-b; Wilson et al., 2005). Delprado et al. (2012) found moderate inter-item reliability, with a Cronbach’s alpha coefficient of 0.75, indicating good internal consistency.

Delprado et al. (2012), in their study assessing the clinical utility of PM measures, including the CAMPROMPT, in predicting amnestic MCI (aMCI) found that the CAMPROMPT had the ability to discriminate aMCI from healthy individuals. So too did two other simple, single-trial event-based tasks of PM, albeit to a lesser extent. They observed that both the time- and event-based scales of the CAMPROMPT were equal in their discriminative ability.

The CAMPROMPT, therefore, appears to be a sensitive test of mild memory and cognitive difficulty.

However, proper administration of the entire CAMPROMPT battery in its present state is unfortunately not feasible in the time-constrained setting of primary care.

Another gap in terms of current practice is the lack of attention paid to the formal assessment of self-reports of memory problems. This, despite the phase 1 aspects of the AWV (Cordell et al., 2013).

The lack of attention granted to self-reports of memory problems in screening tool development, and hence clinical practice, is reflected by the absence of any measure of self-reported memory dysfunction in the ICGP guidelines for cognitive screening in primary care. This absence of a subjective assessment is regrettable, given the mounting literature supporting the validity and utility of self-reported memory failures for detecting cognitive impairment, which will be outlined next.

According to Cullen et al. (2007), the ideal screen is not only statistically robust but also qualitatively rich, allowing referring clinicians to better describe a patient's symptom profile, and lending itself to use in a wider range of settings. In this regard, it is surprising that the qualitative information conferred by self-reported accounts of memory problems has not been utilised fully to date in a cognitive screening tool for the primary care setting, and, in particular, for the detection of very early potential impairment, since older adults have shown to possess accurate insight into subtle cognitive changes experienced by them (Dufouil, Fuhrer & Alperovitch, 2005; Jessen et al., 2010).

63 2.4.3 Subjective Assessment: self-reported difficulties:

As outlined earlier , self-reported cognitive and memory failures are common in elderly people living in the community (Geerlings, Jonker, Boute, Ader & Schmand, 1999; Jonker, Geerlings & Schmand, 2000) as well as amongst those attending primary care (Waldorff et al., 2012). Recently, a longitudinal study by Reisberg, Shulman, Torossian, Leng & Zhu (2010 ) showed that those with subjective cognitive or memory decline were 4.5 times more likely to progress to MCI and dementia that were those without. Indeed, on the basis of findings from a number of longitudinal clinical and population-based studies, self-reported cognitive failures are now proposed to constitute an early symptom of cognitive impairment or dementia (e.g. Johansson, Allen-Burge & Zarit, 1997; Schamnd, Jonker, Geerlings & Lindebooom, 1997; Schofield et al., 1997; Geerlings, Jonker, Bouter, Ader & Schmand, 1999; Jorm, Christensen, Korton, Jacomb, &

Henerson, 2001), even in the absence of objective cognitive decline (Dufouil et al., 2005; Wang et al., 2004), and after adjustment for depressive symptomatology (Jonker et al., 2000). Their importance is reflected in their inclusion in the Diagnositic and Statistical Manual (DSM) 5 criteria for Minor Neurocognitive Disorder.

Biomarker evidence, such as brain activation on functional imaging (Erk et al., 2011), cerebral hypometabolism (Scheef et al., 2012), grey matter volume loss (Saykin et al, 2006), amyloid accumulation (Perrotin, Momino, Madison, Hayenga & Jagust, 2012) and cerebrospinal fluid markers (Visser et al., 2009) lend putative objective support to older adults’ self-perceived changes in cognition regardless of their performance on cognitive tests or intact daily functioning.

The significance of self-reported memory problems are signified by their inclusion in traditional MCI criteria, as well as clinical staging systems for dementia, and diagnostic systems such as DSM 5 (which now refers to dementia as Major Neurocognitive Disorder and MCI as Minor Neurocognitive Disorder) and the International Statistical Classification of Diseases and Related Health Problems (ICD-10; World Health Organisation, 1992). Arguably, it is also feasible to assume that self-report assessments may represent a less invasive or less stressful, and more acceptable means of assessment of cognition to older adults, and therefore present less risk of disruption to the therapeutic relationship between the GP and older person.

Despite all of this, the relevance of self-reported memory failures has been questioned, with an extensive literature suggesting that there is little relationship between subjective complaints and objective test performance (e.g. Jungwirth et al., 2004; Minette, Da Silva, Ortiz & Bertolucci, 2008).

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According to some authors, heterogeneity in study methodology (the use of clinical versus non-clinical samples, differences in the assessment and measurement of subjective memory problems and the use of cross-sectional designs, as well as the differential treatment of associated variables) is the main reason for the lack of a significant relationship (Jonker et al., 2000; Montejo, Montenegro, Fernandez & Maestu, 2012).

Other reasons proposed for lack of an observed relationship between subjective and objective test performance are the low correspondence of the cognitive tests typically employed to assess objective function with real-world cognitive functioning i.e. lack of ecological validity (Shilling & Jenkins, 2007).

Another, as detailed earlier in this chapter, is the lack of sensitivity of many of the tests used to examine the relationship between subjective and objective tests are, in essence cognitive screening tools with questionable sensitivity to mild dementia and MCI (Rabin, Smart & Amariglio, 2017).

Shortcomings in the instruments used to assess self-reported cognitive functioning might also explain the lack of observed relationships between subjective and objective performance (Lai et al., 2009).

These limitations include the observation that metamemory (beliefs about one’s own memory) does not always correlate with actual memory performance as assessed by objective tests and clinical observations (Craik, Anderson, Kerr and Li, 1995; Morris, 1984). Respondents may also have limited insight into their memory problems (Herrman, 1984), or people with memory failures may forget about their errors (Cohen, 1996). Findings concerning the relationship between subjective and objective memory may also be influenced by the nature and number of self-reported memory problems. Previous research on the relationship between the type and number of self-reported memory failures and performance on objective cognitive tests has shown that some subjective failures, such as difficulty following a group conversation, or finding one’s way around familiar streets, were more highly associated than other subjective failures with odds of cognitive impairment. For each additional subjective memory problem endorsed, the odds of cognitive impairment increased approximately 20% when each SMC was weighted equally (Amariglio, Townsend, Grodstein, Sperling & Rentz, 2011).

There are many possible approaches and measures for eliciting and assessing subjective cognitive or memory complaints, which, although correlated with each other, yield different results (Reid &

MacLullich, 2006; Abdulrab & Heun, 2008).

These methods range from using a single or just a small number of general complaint questions (e.g. Do you have trouble with your memory?) accompanied by a yes/no response format, or questions with a scaled/graded response format (e.g. asking participants to rate their memory at the present time from

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poor to excellent, or asking participants to rate their memory compared to others of the same age, etc.), to subsets of scored questions from diagnostic and screening instruments for the elderly with a cut-off score indicating subjective memory impairment. Other studies have employed structured questionnaires with multiple items designed to indicate the severity or frequency of memory failures (Abdulrab & Heun, 2008).

Many studies have limited the assessment of perceived or self-reported cognitive dysfunction to a single domain of memory (episodic or retrospective), often including only a single question about perceived forgetfulness. Typical of this approach is the question used for assessing memory complaints in the older Irish population aged 50 years and above in The Irish Longitudinal Study of Aging (TILDA; Barret, Burke, Cronin, Hickey & Kamiya, 2011). In that study, participants are asked to rate their memory as excellent, very good, good, fair, or poor. However, a structured, specific self-report questionnaire is preferable for providing a more detailed insight of the exact nature, type and frequency of self-reported forgetfulness in the general population.

A specific questionnaire on subjective memory complaints was also found to be preferable to an instrument that uses an aggregate of complaints questions on self-reported memory for detecting associations between self-reported memory problems and other variables in community-dwelling older adults (Montejo et al., 2014). Such associated variables, some of which are outlined further below in this chapter, may represent useful predictors of subjective cognitive and memory complaints.

It is also imperative that such a questionnaire assesses domain(s) other than episodic/retrospective memory alone (Cullen et al., 2007); the importance of this is underlined by the prevalence of deficits in cognitive domains other than episodic memory revealed in detailed neuropsychological testing of patients with MCI (Ribiero, de Mendonca & Guerreiro, 2006).

Prospective memory (PM) referring to memory for future plans and intentions (Einstein & McDaniel, 2000) is a complex, multifactorial type of memory, often involving processes beyond those involved in retrospective memory (RM), such as planning, monitoring, maintenance, initiation, and implementation of intentions (Kliegel, McDaniel & Einstein, 2000). Of direct relevance to this study is the fact that the content of memory complaints generally relate to PM tasks more than RM tasks (Mantyla, 2003).

Prospective memory failures are common in the older general population; The Irish Longitudinal Study of Aging (TILDA) reported that of adults aged 80 and over, 42% forgot to carry out an action they had earlier been instructed to perform (Barrett, Burke, Cronin, Hickey & Kamiya (2011). PM is believed to be more vulnerable than RM to impairment in dementia (Huppert & Beardsall, 1993) and a more pronounced

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deficit than RM failure in a study of people with MCI; therefore, PM deficits have been suggested to have predictive validity for the development of cognitive impairment above and beyond RM deficits (Blanco-Campal et al., 2009).

The content of memory complaints generally relate to PM tasks more than RM tasks (Mantyla, 2003) and from a more holistic social prescribing perspective such failures are important for primary care professionals to assess since they can have serious consequences for medication management (Woods et al., 2014) and completion of instrumental activities of daily living (Woods, Weinborn, Veinoweth, Rooney

& Bucks, 2012).

The Prospective and Retrospective Memory Questionnaire (PRMQ; Smith, Maylor, Della Sala and Logie, 2000) is the only validated standardised questionnaire that assesses prospective and retrospective memory difficulties to an equal extent. Importantly, the PRMQ is also accompanied by normative data obtained from a UK population sample by Crawford, Smith, Maylor, Della Sala and Logie (2003). These normative data represent a highly useful benchmark against which practitioners and researchers in the UK can make a reliable comparison of an individual’s self-rated memory difficulties to memory difficulties reported by those of a similar age and sociodemographic background. Distribution of the PRMQ (as opposed to a single global memory complaint question, or any number of single episodic/retrospective memory domain questions) therefore provides a more comprehensive account of what can be considered usual in the general population in terms of the type and frequency of forgetfulness. It also provides opportunity for the establishment of normative data specific to the older Irish population, the need for which is suspected from cross-national comparisons of memory and health data more generally.

For example, data from the TILDA study showed that Irish people self-reported better memory than their English counterparts (Savva, Maty, Setti & Feeney, 2011), indicating differences between the two national populations in self-perceived memory difficulties.

Although the TILDA study employed a single general item asking people to self-rate their memory at the present time as excellent, very good, good, fair, or poor, other findings in the literature reveal significant differences in mean scores on the PRMQ between countries, specifically Sweden and the UK (Ronnlund, Mantyla & Nilsson, 2008), further highlighting the potential need for country-specific normative data for self-reported memory failures.

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2.5 Factors impacting on memory (self-reported and/or objective)