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2.5.1.1 Age: Since there is a general decline in cognitive functioning with age (Jonker et al., 2000), an association between age and self-reported memory failures may be expected. However, findings in this regard have differed (Montejo et al., 2014). While an association between memory complaints and increasing age has been demonstrated in many studies (e.g. Trouton, Stewart & Prince, 2006; Montejo et al., 2011), this relationship is not conclusive. For example, Jorm et al. (1997) found no relationship between increasing age and either a general question about memory complaints or an eight-point scale of specific questions about everyday memory problems, and Montejo et al (2014) did not find a significant correlation between self-reported memory failures, measured by a structured questionnaire or three complaint questions, and the age variable. Neither did age influence PRMQ scores in middle-aged and older people in UK samples in several investigations (Crawford et al., 2003;2006; Smith, Della Sala, Logie

& Maylor, 2000). In contrast, Ronnlund et al (2008) found that higher age was associated with minor decrements in self-reported PM failures on the PRMQ in a Swedish sample. A lack of age effects in studies of subjective cognition may be attributable to the normalisation of perceived memory failures due to ageing expectations, social comparison, or attributing forgetfulness to other conditions (e.g. Hodgson &

Cutler, 2004; Prohaska, Keller, Leventhal & Leventhal, 1987; Connell & Gallant, 1996; Werner, 2003; Oritz

& Fitten, 2000; Wackerbath & Johnson, 2002).

2.5.1.2 Gender: Findings related to the effects of gender on self-reported memory failures are inconsistent. Crawford et al (2003) found that women reported fewer retrospective memory failures than men on the PRMQ. This is in contrast to a study using the PRMQ in Brazil, which found women reported more retrospective and prospective memory than men. Other clinical and population-based studies using the PRMQ show that female gender is generally associated with more subjective memory failures (Jonker et al., 2000; Crook, Feher & Larabee, 1992), and some authors have attributed this to the higher prevalence rates of depression in females compared to males (e.g. Jorm et al, 1997). However, Montejo et al (2011) found that females reported significantly more subjective memory problems than men even after controlling for depression and anxiety. In contrast, Mendes et al (2008), using the Subjective Memory Complaints (SMC) scale (Schmand et al., 1996) found no gender effect of self-reported memory failures. Similarly, TILDA reported no significant difference between men and women in response to a single item of self-rated memory (Barrett et al., 2011).

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2.5.1.3 Education: Findings regarding the effect of education on self-reported memory are inconclusive, with methodological differences being cited as the reason for this. Some studies (e.g. Blazer et al., 1997;

Savva et al., 2013) found associations between education and self-reported memory failures such that a low level of education is associated with more reported failures , and the TILDA study also found self-rated memory assessed by a single item was poorer in those with low education, and this association was most pronounced in the young-old, i.e. 50 – 64 year age group (Barrett, Burke, Cronin, Hickey and Kamiya (2011). Other studies have demonstrated more self-reported memory failures in subjects self-reporting a higher level of education (e.g. Comijs, Deeg, Dik, Twisk & Jonker, 2002). A review of clinical and population-based studies concluded that memory complaints in highly educated elderly subjects may be predictive of dementia even when there is no indication of cognitive impairment on short cognitive screen tests (Jonker et al., 2000).

2.5.1.4 Marital Status: Marital status is a significant social factor associated with health and cognition (Mousavi-Nasab, Komi-Nouri, Sundstrom & Nilsson, 2012). Despite the positive associations between marital status and various health factors (Mousavi-Nasab et al., 2012), there appear to be fewer studies that have specifically reported the relationship between marital status and either objective or subjective cognitive functioning. However, marital status was seen to exert effects on objective episodic and semantic memory on healthy milddle-aged and old adults in a longitudinal population-based study in Sweden (Mousavi-Nasabi et al.,2012), such that married people showed significantly better performance on recall and recognition subtests of episodic memory. The rate of decline was also significantly larger for singles and widowed than other groups over the 5-year period across all ages.

A few studies do confirm a relationship between marital status and Alzheimer’s disease (AD) and show an excess risk for development of AD among never-married individuals (e.g. Helmer et al., 1999). In general, living without a partner appears to confer an increased risk for development of cognitive impairment and dementia (Hakansson et al., 2009).

Fewer studies report the direct relationship between self-reported memory ability and marital status.

However, in Israel, a large sample of community dwelling older adults’ participants with and without self-reported memory failures did not differ in marital status (Balash et al., 2013).

Marital status of people aged 50 and above in Ireland however exhibits a unique marital status pattern compared with many other European countries due to our unique historical inheritance pattern. Marital status here differs as a function of education and gender, with the proportion of men who never married

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decreasing with increasing educational attainment but more highly educated women being less likely to have married, relative to those with second level schooling (Barrett et al., 2011).

The marital status response categories in the current study were mirrored from the most recent Irish Census and included a response option for Civil Partnership.

2.5.1.5 Occupation: Objective cognitive impairment has been found to be more prevalent in individuals with low-qualification occupations than in those with high qualification occupations (Juncos-Rabadan et al., 2012). Cognitively complex or demanding work was shown to confer a protective effect on cognitive ability in later life in both men and women (Shcooler, Mulatu & Oates, 1999; Smart, Gow & Deary, 2014).

In a sample of US veterans, the effect was independent of education and intelligence (Potter, Helms &

Plassman, 2008). Considerably less attention has been granted in the literature to the association of current or previous occupation with subjective memory.

Several variables are known to impact memory and are of interest in their own right as predictors of objective and self-reported and cognitive problems (Cutler & Grams, 1988). Each of these factors may impact on subjective and objective memory performance and may confound the relationship between subjective and objective cognitive performance (Montejo et al., 2014). A deeper understanding of these variables relating to sociodemographic characteristics, mood state, sleeping difficulties and physical health, that may be associated with self-reported memory failures could arguably help Primary Care professionals to better identify individuals at an early stage of cognitive decline or subtle cognitive impairment or increased risk for further cognitive deterioration. Information regarding significant associations of other variables to subjective memory complaints are also helpful in the context of identifying individuals who might benefit from social prescribing, i.e. non-clinical interventions usually involving referral to local voluntary services and community groups (Brown, Friedli & Watson, 2004).

Drawing on the findings of Hart, Burns, Brown and Barrowclough, (2012), Steinberg and colleagues (2013) argue that greater awareness is needed regarding the value of measuring self-reported memory problems among both practitioners and individuals in the community. Since many older adults do not complain about, or seek help for, their memory (Waldorff et al., 2008; Commissaris et al., 1993), even though these concerns can cause considerable distress to them (Commissaris et al., 1998; Mol et al., 2007), more extensive knowledge of the associations of self-reported memory failures with other variables may give practitioners a greater appreciation for the value of assessing or inquiring as to an older individual’s cognitive functioning.

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The decision to assess may be more easily informed by the presence of certain comorbid symptoms or person characteristics, and on the other hand, memory complaints themselves may be an indicator of the presence of these other symptoms or conditions that may warrant attention in and of themselves.

Knowledge of other variables associated with subjective memory ability can therefore help GPs to be more adept at identifying individuals with subtle cognitive dysfunction so that they can implement interventions to help build and maintain cognitive resilience or assist older adults with implementing lifestyle changes to prevent further cognitive decline.

Depression, in particular, has shown consistent associations with self-reported memory failures and objective memory performance (Gagnon et al., 1994; Derouesne et al., 1999), and an increasing number of studies show an association with anxiety (e.g. Steinberg et al., 2013; Hanninen et al., 1994; Derouesne et al., 1999). Assessment of self-reported depression and anxiety were, therefore, included in the methodology of the current thesis, alongside other demographic variables associated with self-reported memory, albeit inconsistently – age, gender and education – as well as health-related variables and sleep variables.

The rationale for assessment of each of these variables when assessing memory is outlined below.

2.5.1.6 Impact of mood state (anxiety and depression)

Numerous studies, of both community volunteers (Montejo et al., 2011) and self-referred memory clinic attendees (Bolla et al., 1991; Derouesne et al., 1999) have shown that self-reported memory failures are strongly associated with self-reported symptoms of depression. Higher PRMQ scores, reflecting poorer self-reported memory, were associated with subclinical depression as measured by the Geriatric Depression Scale (GDS) in one study of healthy older community dwelling adults aged 65 years and above (Steinberg et al., 2013). Memory complaints are more common in those with self-reported depression than in those without (Montejo et al., 2011), and self-reported depression is often a stronger predictor of self-reported memory problems than objective cognitive status in cross-sectional studies (e.g. Jonker et al., 1996; Grut et al., 1993; Bolla et al., 1991). Depression also negatively affects cognitive ability as measured by objective tests (Montejo et al., 2014). In particular, memory problems reported by self-referrals to a memory clinic (Bolla et al., 1991; Barker, Prior & Jones, 1995; Derouesne, Guigot & Chatellier, 1995) were more often correlated with depressive symptoms than poor objective cognitive performance.

Depressive symptoms in and of themselves are claimed by some authors to predict the development of dementia (Gatz, Tyas, St. John & Montgomery, 2005), while other authors propose they are early manifestations, rather than predictors, of Alzheimer’s disease (Chen, Ganguli, Mulsant & DeKosky, 1999).

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In line with this latter theory, subjective memory failures in those self-reporting depression may be reflective of a genuine cognitive deficit, indicative of an early pathological dementia process presenting as depression. Alternatively, perceived failures of everyday memory may be a result of poor motivation or concentration resulting from depression (Jae-Min, Stewart, Il-Seon, Sung-Ku & Jin-Sang, 2003), as mood disorders themselves may present with a distinct pattern of cognitive impairment (Austin, Mitchell &

Goodwin, 2001). Tobiansky, Blizard and Livingston (1995) studied a community sample of elderly residents with a 2-year follow-up period and found that subjects with self-reported memory problems were at a four-fold increased risk of developing dementia, and a two-fold increased risk of developing depression.

Self-reported memory failures are therefore of interest as potential predictor or risk factor for depression even in people with no previous history of depression (Heun & Hein, 2005).

Depression and subthreshold depression is common in the general population in Ireland, with 10% of the population reporting clinically significant depressive symptoms and a further 18% reporting “sub-threshold” levels of depression in the TILDA study, with a large percentage of cases (78%) going undiagnosed (Barrett et al., 2011). As even subthreshold levels of depression lead to cognitive changes (Martinez-Aran et al., 2004) it was deemed important for the purpose of this study to assess self-reported depression and to explore its relationship with self-reported memory failures in otherwise healthy community dwelling older adults.

Research also demonstrates a relationship between self-reported anxiety and self-reported memory ability in community dwelling adults (e.g. Balash et al., 2013) as well as in clinical samples (e.g. Schilling

& Jenkins, 2007). Higher PRMQ scores correlated with both higher self-reported depression and anxiety as measured by the DASS anxiety subscale in a study of community dwelling older adults followed for 3 years (Steinberg et al., 2013). Although the overall levels of depression and anxiety in the sample were considered low by normative standards in that study, the association persisted. Anxiety is known to negatively impacts objective cognitive performance (Eyesenck, Derakshan, Santos & Calvo, 2007) and the relationship between late-life anxiety and cognition appears to be reciprocal (Beaudreau & O’Hara, 2008) and has been proposed as strong predictor for future cognitive decline, either directly, or indirectly (via depression) (Sinoff & Werner, 2003). However, the effects of anxiety symptoms on cognition have been less well studied than depression, and findings regarding the predictive validity of anxiety for cognitive impairment and dementia have been inconsistent; for example, Gallagher et al., 2011 concluded that anxiety symptoms were not independent of cognitive function at baseline, and so may be a marker of severity of cognitive impairment rather than a risk factor.

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In Ireland, the TILDA study revealed that anxiety and subthreshold anxiety are very common in the older general population, and anxiety is more common in this age group than depression. 13% of the TILDA sample reported clinical level anxiety, and 29% reported subclinical levels of anxiety. Like depression, anxiety also goes undiagnosed in many older Irish people. 85% of older Irish adults who presented with objective anxiety in the study did not report a doctor’s diagnosis. Based on all the above findings, it was considered important to include anxiety as a variable for assessment in the present survey study, and to explore its relationship to self-reported memory.

2.5.1.7 Sleep: Difficulties sleeping are common across the lifespan (Stojanovski, Rasu, Balkrishnan &

Nahata, 2007; Hayley et al., 2015) and are not an inevitable part of aging. Potential reasons for sleep difficulties include medical and psychiatric illness, the medications used to treat these illnesses, circadian rhythm changes, or other sleep disorders (Ancoli-Israel & Ayalon, 2006).

Sleep quality and quantity problems experienced by older adults include problems with sleep onset (being able to fall asleep quickly) and sleep maintenance (staying asleep throughout the night) (Hartescu, Morgan & Stevinson, 2016) as well as early morning arousal (Foley et al., 1995). Sleep disturbances are common in people with dementia (Grace, Walker & McKeith, 2000). Poor sleep quality and deficiency may be a risk factor for cognitive impairment and Alzheimer’s Dementia (AD) (Codazo-Minguez & Cowburn, 2001), possibly because sleep deprivation induces more build-up of the protein Amyloid Beta in the brain, while adequate sleep reduces it. The build-up of Amyloid Beta may also cause disturbed sleep patterns and increased wakefulness (Ju, Lucey & Holtzman, 2014). Reflecting this, community-dwelling older individuals with early amyloid deposition but without MCI have been found to self-self-report cognitive problems (Spira et al., 2013).

A chronic sleep restriction experiment in younger adults demonstrated a dose-response effect of chronic restricted sleep periods of 4 to 6 hours per night over 14 consecutive days on cognitive performance (Van Dongen, Maislin, Mullington & Dinges, 2003). The inclusion in the present study of a self-report question assessing the self-perceived length of time older participants have been experiencing sleep difficulties enables exploration, if one wishes, of the cumulative subjective effects of sleep difficulties over an even longer time span (from less than 1 month to 11 or more years). Similarly, obtaining self-perceived reason(s) for these sleep difficulties help to clarify the relationship between subjective sleep problems and subjective memory complaints and to determine correlates or predictors of poor subjective sleep quantity and quality which may form targets for primary preventive intervention by primary care professionals.

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2.5.1.8 Physical Conditions: The link between physical and cognitive health.

The search for early signs of cognitive decline, of which self-reported memory failures can be one part, has led also to increasing interest in the connection between adverse physical health and cognitive problems. Cognitive frailty is a recent construct referring to a heterogeneous age-related clinical syndrome wherein physical frailty co-occurs with reversible cognitive impairment (Ruan et al., 2017). Both physical frailty and cognitive impairment may interact with each other in a cycle of decline (Robertson et al., 2013). Chronic diseases and other health conditions of varying severity may act alone or in combination to exacerbate frailty, and vice-versa. Even treatment of pre-existing physical health conditions may have side-effects which further contribute to both physical frailty and/or the cognitive frailty syndrome (Weiss, 2011). Chronic diseases and other significant health conditions are therefore of interest in relation to the assessment of subjective and objective memory.

Weiss (2011) lists the chronic diseases that have been associated with frailty in published cohort studies of older adults such as the Women’s Health and Aging Studies I and II, the Ivecchiare in Chianti Study and the Cardiovascular Health Study, all of which used standardised forms of disease ascertainment. These are; hypertension, chronic kidney disease, osteoarthritis, depressive symptoms, coronary heart disease, diabetes mellitus, chronic lower respiratory disease, myocardial infarction, rheumatoid arthritis, stroke, peripheral arterial disease, and congestive heart failure.

An association between self-reported physical ill health and subjective memory was demonstrated in a 6-year follow-up of the Amsterdam Longitudinal Study of Aging (LASA) cohort (Comijs et al., 2002), such that participants with memory complaints reported more chronic diseases at all three measurement occasions in the study. Montejo et al (2011) found that self-perceived health – over and above depression and anxiety – was an independent predictor of subjective memory complaints. Similarly, Cutler and Grams (1988) found that health was one of the best predictors of everyday memory problems.

Health conditions assessed in the questionnaire used in the present study are cardiovascular disease:

hormonal problems, breathing problems, diabetes, chronic pain, arthritis:, conditions arising from dysfunction of the enteric nervous system (ENS): gastric problems, ulcerative colitis, Crohn’s disease, thyroid disorders. For the interested reader, a very brief overview of these complaints is provided in Appendix A.

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Ireland has one of the highest levels of alcohol consumption in the European Union (European Commission, 2010). It is well established that habitual excess alcohol intake is harmful to the brain and cognitive function (Chick et al., 1989), interfering for example with the ability to form new long-term memories (White, 2003). Long term excessive intake is associated with cognitive impairment and dementia (Kim et al., 2012). However, some studies have documented better cognitive test scores among moderate drinkers (e.g. Dufouil, Ducimetiere & Alperovitch, 1997; Stampfer, Kang, Chen, Cherry &

Godstein, 2005). In terms of the association between alcohol use and self-reported memory failures, it was difficult to identify studies that reported specific findings on this relationship.