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. Author manuscript; available in PMC: 2019 Nov 1.
Published in final edited form as: Neuropsychology. 2018 Jul 26;32(8):931–940. doi: 10.1037/neu0000437

Antecedents and Consequences of Unawareness of Memory Impairment in Dementia

Robert S Wilson 1, Lisa L Barnes 1, Kumar B Rajan 2, Patricia A Boyle 1, Joel Sytsma 1, Jennifer Weuve 3, Denis A Evans 2
PMCID: PMC6234063  NIHMSID: NIHMS980601  PMID: 30047756

Abstract

Objective:

To assess the prevalence, antecedents, and consequences of unawareness of memory impairment in dementia.

Methods:

Persons (n=1,862) from a geographically defined community without dementia at enrollment subsequently underwent clinical classification (248 with dementia, 611 with mild cognitive impairment, 1,003 with no cognitive impairment), memory testing, and self-appraisal of memory. Memory performance was regressed on self-appraised memory, and the residuals served as an index of memory awareness. After clinical classification, participants completed brief cognitive testing at three-year intervals for up to 15 years.

Results:

When unawareness was defined as a score at or below thresholds ranging from the 15th to 25th percentiles, it was more common in dementia (67% - 83%) and mild cognitive impairment (15% - 33%) than in no cognitive impairment (2% - 6%; all p<0.001). A continuous measure of awareness (mean=0.00, SD=0.61) was reduced by 0.37-unit in mild cognitive impairment (SE=0.04, p<0.001) and 1.04-unit in dementia (SE=0.06), p<0.001) compared to those without cognitive impairment, and these associations were weaker in Black persons than White persons (estimate for dementia by race=0.37, SE=0.12, p=0.003; estimate for mild cognitive impairment by race = 0.30, SE=0.08, p<0.001). Higher premorbid neuroticism was associated with better memory awareness in dementia. Higher memory awareness was not related to mortality in mild cognitive impairment or dementia but had a marginal association with slower cognitive decline in mild cognitive impairment.

Conclusions:

Unawareness of memory impairment is a common manifestation of dementia, particularly in White persons, but is not strongly related to adverse disease outcomes.

Keywords: anosognosia, dementia, neuroticism, mortality, cognitive decline

Introduction

Unawareness of memory impairment is frequently observed in older persons with dementia and its precursor, mild cognitive impairment (MCI) (Roberts, Clare, & Wood, 2009; Wilson, Sytsma, Barnes, & Boyle, 2016). Although this phenomenon has been extensively investigated, knowledge about it remains limited, owing in part to methodologic factors. First, most previous studies have been conducted on groups selected from health care settings (Starkstein, Jorge, Mizrahi, & Robinson, 2006; Castrillo Sanz et al., 2016; Yoon et al., 2017) rather than groups sampled from defined populations (Mograbi et al., 2012; Mograbi et al., 2015), so that it is hard to accurately estimate how often it occurs. Second, many measures of memory awareness are based on informant report which is weakly associated with memory performance (Farias et al., 2004; Farias et al., 2013) and subject to bias (Clare, 2004; Razani et al., 2007; Martyr, Nelis, & Clare, 2014). Third, most prior research has been cross-sectional, and most longitudinal studies have been conducted on small groups (<100 participants [Starkstein et al., 1997; Vasterling, Seltze, & Watrous, 1997; Derouesne et al., 1999; Akai et al., 2009; Kiyak, Teri, & Borson, 1994; Clare & Wilson, 2006; Clare, Nelis, Martyr, Whitaker, et al., 2012; Sousa et al., 2015; Vogel, Waldorff, & Waldemar, 2015]), with brief follow-up periods (<2 years [Starkstein et al., 1997; Vasterling et al., 1997; Derouesne et al., 1999; Akai et al., 2009; Kiyak et al., 1994; Sevush, 1999; Clare & Wilson, 2006; Clare, Nelis, Martyr, Whitaker, et al., 2012; Sousa et al., 2015]), and low (Starkstein et al., 1997; Derouesne et al., 1999; Vogel et al., 2015) or indeterminate (Vasterling et al., 1997; Aki et al., 2009; Kiyak et al., 1994; Sevush, 1992; Clare & Wilson, 2016; Clare, Nelis, Martyr, Whitaker, et al., 2012; Sousa et al., 2015) rates of follow-up participation, making identification of its antecedents and consequences difficult.

To confront these challenges, the present analyses are based on participants sampled from a defined population, a longitudinal study design with up to 15 years of follow-up, and a previously established measure of memory awareness that does not rely on informant report. We used this platform to examine the level of awareness of memory impairment in MCI and dementia and identify its antecedents and consequences.

Previous research suggests that declining awareness of memory impairment in old age is driven in large part by dementia related pathologies, particularly neurofibrillary tangles, transactive response DNA-binding protein 43 pathology, and gross cerebral infarcts (Wilson, Boyle, Yu, et al., 2015). It is uncertain, however, whether there are factors that make awareness more or less vulnerable to these neurodegenerative and cerebrovascular changes in the brain (Mograbi, Brown, Landeira-Fernandez, & Morris, 2014). We focused on two sets of antecedents. First, because demographic variables are related to cognitive functioning (Wilson et al., 1978), we assessed whether awareness of memory impairment in MCI or dementia differed along demographic lines. We were particularly interested in the possibility of racial/ethnic differences given that dementia appears to be more common among Black persons than White persons (Tang et al., 2001; Chin, Negosh, & Hamilton, 2011; Yaffe et al., 2013), but rate of cognitive decline appears to be similar or less pronounced in Black persons compared to White persons (Masel & Peck, 2009; Wilson, Capuano, Sytsma, Bennett, & Barnes, 2015; Weuve et al., 2017). Second we tested whether premorbid personality modified memory awareness in MCI or dementia. Although psychosocial factors are hypothesized to influence anosognosia in dementia (Clare, Nelis, Martyr, Roberts, et al., 2012), most published data consist of cross-sectional correlations between anosognosia and neuropsychiatric symptoms seen in dementia such as apathy (Spalletta, Giradi, Cattagirone, & Orfei, 2012; Mograbi & Morris, 2014; Mak, Chin, Ng, Yeo, & Hameed, 2015). A more basic questions is whether premorbid psychological characteristics increase or decrease awareness in dementia. One study found higher premorbid conscientiousness to be associated with lower awareness in dementia (Seiffer, Clare, & Harvey, 2005) but another study found no association of conscientiousness or other big five traits with memory awareness (Gilleen, Greenwood, Archer, Lovestone, & David, 2012). Interpretation of these mostly negative results is difficult, however, because assessing premorbid personality by retrospect informant report likely involves substantial error. To confront this issue, personality in the present study was assessed by self-report at baseline when all participants were deemed free of dementia.

Longitudinal research has shown that awareness of memory impairment progressively diminishes in those with dementia (Wilson, Boyle, Yu, et al., 2015). After adjustment for its association with dementia severity, however, it is not clear whether anosognosia is associated with adverse disease consequences. Few longitudinal studies have addressed this issue (Perales et al., 2016; Aatten et al., 2006). Further, most studies have used informants to assess awareness, its consequences, or both, possibly biasing estimates of their association. In the present study, we focused on rate of cognitive decline over time, a core manifestation of dementia, and risk of death, consequences of MCI and dementia that do not rely on informant report, and tested the hypothesis that lower level of memory awareness in MCI and dementia predicts more adverse consequences.

Methods

Participants

Analyses are based on persons from the Chicago Health and Aging Project, a population-based longitudinal cohort study of risk factors for Alzheimer’s disease and other common chronic conditions of old age (Bienias, Beckett, Bennett, Wilson, & Evans, 2003). Beginning in 1993, a geographically defined area on the south side of Chicago was censused. Those aged 65 years or older were invited to participate in a highly structured in-home interview lasting approximately 90 minutes. The interview included questions about demographic information and a wide range of possible risk factors for dementia, brief tests of cognitive function (see section on Longitudinal Assessment of Cognition) and physical performance, and anthropometric measurements, as previously described (Bienias et al., 2003). A stratified random sample of the population was invited to undergo a detailed clinical evaluation to diagnose MCI, dementia, and Alzheimer’s disease (see section on Clinical Evaluation). Three years later, the full population was re-interviewed and a clinical evaluation was done on a random stratified sample of those judged free of dementia in the previous wave of data collection. The interview of the entire population and clinical evaluation of a previously dementia free subset were repeated at three-year intervals for another 4 waves of data collection. Thus, the study included longitudinal (triennial interview of full population) and cross-sectional (detailed clinical evaluation of different subsets of the population) components. The institutional review board of Rush University Medical Center approved the project (ORA number: L92012402-CR09) and all participants signed informed consent forms.

A total of 5,552 persons were deemed free of dementia in wave 1, and 2,835 were subsequently invited to participate in a detailed clinical evaluation. Of these, 179 died before the evaluation and 1,862 of 2,656 survivors (70.1%) completed it. Their mean age at the time of the clinical evaluation was 79.5 years (SD = 5.9). They had completed a mean of 13.2 years of schooling (SD =3.3) and 1,166 (62.6%) were women. We assessed race/ethnicity, an important social indicator, by asking the participant: We need to know about your ethnicity. What do you feel is the racial category which best describes yourself?” The responses in the analytic group were: 913 White, 944 Black, 2 American Indian, 3 Asian/Pacific Islander. For analyses, race/ethnicity was collapsed into Black (n=944) and predominantly White (n=918) subgroups, as in previous research (Wilson et al., 2005; Wilson, Rajan, Barnes, Weuve, & Evans, 2016).

Eligibility for analyses to assess change in cognitive function required completion of at least one population interview after the clinical evaluation (which would provide two cognitive measurement points, the minimum needed to be included in longitudinal models). This eliminated 197 individuals seen in the final clinical evaluation. Of the remaining 1,665 persons, 274 died before the next population interview leaving 1,391 eligible for follow-up, and 1,343 of these (96.5 %) completed at least one follow-up population interview. The 1,343 with cognitive follow-up were younger than the 519 without cognitive follow-up (79.2 vs 80.5, t[841.6]=4.6, p<0.001), but the subgroups did not differ in education (13.2 vs 13.1, t[1,860]=0.6, p=0.570), percent of women (69.7 vs 73.6, χ 2 [1]=3.3, p=0.069), or percent of Black persons (71.6 vs 73.3, χ 2 [1]= 1.3, p=0.261).

Clinical Evaluation

Participants selected for detailed clinical assessment underwent a uniform evaluation that included a structured medical history, neurological examination, and a battery of 20 cognitive tests (Wilson et al., 2009; Wilson et al., 2010). Most persons were only selected once for detailed clinical evaluation; in those who had more than one clinical evaluation, we used the earliest (to maximize duration of follow-up). The cognitive tests were administered by a trained research assistant in an approximately one hour session. In addition to the Mini-Mental State Examination, they included 7 measures of episodic memory: immediate and delayed recall of 12 ideas in the East Boston Story (Albert et al., 1991; Wilson et al., 2002) and 25 ideas in Logical Memory Story A (Wechsler, 1987) plus Word List Memory, Word List Recall, and Word List Recognition (Welsh et al., 1994; Wilson et al., 2002). There were 4 language measures: short forms of Complex Ideational Material (Wilson et al., 2002) and Boston Naming Test (Welsh et al., 1994), verbal category fluency (Welsh et al., 1994; Wilson et al., 2002), and a 10-item word reading test (Wilson et al., 2009). Working memory was assessed with Digit Span Forward, Digit Span Backward, and Digit Ordering (Wechsler, 1987; Wilson et al., 2002). Perceptual speed was assessed with modified versions (Wilson et al., 2002) of Number Comparison (Ekstrom, French, Harman, & Kermen, 1976) and the oral form of the Symbol Digit Modalities Test (Smith, 1982). Visuospatial ability was assessed with a 15-item version of Judgment of Line Orientation (Benton, Sivan, Hamsher, Varney, & Spreen, 1994) and a 10-item version of Standard Progressive Matrices (Raven, Court, & Raven, 1992).

On the basis of this clinical evaluation, an experienced clinician diagnosed dementia and MCI. First, an algorithm rated impairment in 5 cognitive domains using educationally adjusted cutoff scores on 11 of the 20 tests (Bennett et al., 2002; Wilson, Boyle, Yang, James, & Bennett, 2015). Second, a neuropsychologist reviewed all cognitive test scores and either agreed with the algorithmic ratings of cognitive impairment or revised them. Third, the experienced clinician diagnosed dementia following the criteria of the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer’s Disease and Related Disorders Association (NINCDS-ADRDA; McKhann et al., 1984) which require a history of cognitive decline and evidence of impairment in at least 2 cognitive domains, one of which must be memory for a diagnosis of Alzheimer’s disease (AD). Those who met AD criteria were classified as “possible AD” if the dementia was atypical or there were other cognition impairing conditions present; otherwise it was classified as “probable AD” (McKhann et al., 1984). Individuals who did not meet dementia criteria but had impairment in at least one cognitive domain were classified as MCI. These MCI criteria have been associated with levels of cognitive decline (Bennett et al., 2002; Boyle et al., 2006; Wilson et al., 2010), mortality (Bennett et al., 2002; Wilson et al., 2009) and dementia related pathology (Bennett et al., 2005) intermediate between levels associated with no cognitive impairment and dementia.

Self-Appraisal of Memory

As part of the clinical evaluation, participants were asked “How often do you have trouble remembering things” with five response options: very often (1), often (2), sometimes (3), rarely (4), never (5). They were also asked “Compared to 10 years ago, would you say that your memory is much worse (1), worse (2), the same (3), a little better (4), much better (5)”. As in previous research, the items were correlated and so the scores were summed to provide a measure of subjective memory ranging from 2 to 10 with higher values denoting better function (Barnes, Schneider, Boyle, Bienias, & Bennett, 2006; Wilson, Boyle, Yu, et al., 2015).

Memory Performance Testing

The battery of 20 cognitive tests used in the clinical evaluation included 7 episodic memory measures (immediate and delayed recall of the East Boston Story and Logical Memory Story A, Word List Memory, Word List Recall, and Word List Recognition). Supported by factor analyses in this (Wilson et al., 2009) and other (Wilson et al., 2002) cohorts, these 7 tests were combined to yield a composite measure of episodic memory. Raw test scores were converted to z scores, using the estimated mean and SD in the population, and the z scores were averaged to yield the composite measure.

Longitudinal Assessment of Cognition

As part of each triennial population interview, four brief cognitive performance tests were administered: immediate and delayed recall of the East Boston Story (Albert et al., 1991; Wilson et al., 2002), the oral version of the Symbol Digit Modalities Test (Smith, 1982), and the MiniMental State Examination (Folstein, Folstein, & McHugh, 1975). Because a single factor accounted for more than 70% of the variance in these tests in a previous analysis, raw scores were converted to z scores, using the population mean and SD from the initial interview, and the z scores were averaged to yield a composite measure of global cognition (Wilson et al., 1999).

Assessment of Premorbid Personality

Premorbid personality was assessed at the first population interview. Neuroticism, which indicates proneness to psychological distress, and extraversion, which denotes sociability, were assessed with 4-item short forms (Wilson, Krueger, et al., 2005) of standard 12-item measures of each trait from the NEO Five Factor Inventory (Costa & McCrae, 1992). Participants rated level of agreement with each item on a 5-point scale (0–4). Item scores were summed to yield trait scores with higher values indicating higher level of the trait. In previous research, the 4-item measures have been shown to be highly correlated with the 12-item measures (Wilson, Krueger, et al., 2005) and to predict important health outcomes such as dementia (Wilson, Barnes, et al., 2005) and death (Wilson, Krueger, et al., 2005).

Statistical Analysis

Memory awareness was assessed once, at the time of the clinical evaluation. We regressed the composite measure of episodic memory performance on the measure of subjective memory and then used the residuals as measures of memory awareness to capture the deviation of memory performance from the level predicted by the memory rating, as previously described (Wilson, Boyle, Yu, et al., 2015). The memory awareness measure was used as the outcome in a series of linear regression models. Because age, education, sex, and race/ethnicity are associated with cognitive function (Wilson et al., 1978), we included terms to account for these effects in all analyses. Each model treated those without cognitive impairment as the reference group which was contrasted with the MCI and dementia subgroups. Subsequent models tested for interactions of demographic variables with the diagnostic markers and added premorbid personality variables. We also assessed the relation of diagnosis to binary measures of memory awareness in logistic regression models.

The relationship of memory awareness to mortality was assessed in a series of proportional hazards models. The first model included terms for demographic variables, MCI, dementia, and memory awareness. The second model added terms for the 2-way interactions of memory awareness with MCI and dementia.

We constructed a mixed-effects model to test whether level of memory awareness modified the relation of diagnosis to rate of cognitive decline. The outcome was a composite measure of global cognition assessed at each triennial interview. Terms were included for time; demographic variables, MCI, dementia, memory awareness, and their interactions with time; and the 2-way interactions of diagnosis with memory awareness and the 3-way interactions of diagnosis by memory awareness by time.

Results

Awareness of Memory Function

At the time of the clinical evaluation, subjective memory scores ranged from 2 to 10 (mean = 5.22, SD = 1.44, skewness = −0.11) and episodic memory performance scores ranged from −1.66, to 1.91 (mean = 0.46, SD = 0.61, skewness = −0.65), with higher values on each measure indicating better memory, and the scores were positively correlated (r = 0.14, p< 0.001). As in previous research (Wilson, Boyle, Yu, et al., 2015), we regressed memory performance on memory ratings and treated the residual deviation of performance from the level predicted by the rating as a measure of memory awareness. Positive values indicate underestimation of memory ability, zero indicates agreement between rating and performance, and negative values indicate overestimation of ability. Memory awareness scores in the full group ranged from −2.28 to 1.39 (mean = 0.00, SD = 0.61, skewness = −0.67).

Memory Awareness in Diagnostic Groups

On clinical evaluation, 1,003 persons had no apparent cognitive impairment, 611 persons had MCI, and 248 persons had dementia. Of those with dementia, 179 were diagnosed with NINCDS-ADRDA probable AD, 53 with NINCDS-ADRDA possible AD, and 16 with other dementias (4 Parkinson’s disease, 1 Parkinson’s disease plus cerebrovascular disease, 3 cerebrovascular disease, 1 depression, 1 Lewy body disease, 6 unknown). As shown in Table 1, those with cognitive impairment were older, less educated, and more likely to be Black than those without cognitive impairment.

Table 1.

Characteristics of the diagnostic groups

Characteristic No Cognitive Impairment Mild Cognitive Impairment Dementia p-value
Age at diagnosis 78.4 (5.5) 80.3 (5.9) 82.3 (5.8) <0.001
Education 13.5(3.2) 12.8 (3.3) 12.5 (3.7) <0.001
Women,% 61.3 66.1 59.3 0.078
Black race/ethnicity % 43.9 59.3 56.9 <0.001
Time to diagnosis 6.6 (3.3) 6.2 (3.3) 6.4 (3.4) 0.073
Neuroticism 5.1 (2.2) 5.3 (2.2) 5.4 (2.3) 0.033
Extraversion 8.7(2.1) 8.6(2.1) 8.4(2.3) 0.121
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*Note. Data are presented as mean (standard deviation) unless otherwise indicated. P-values are based on analyses of variance for continuous measures and chi-square for dichotomous measures.

Figure 1 shows substantial heterogeneity in memory awareness within diagnostic groups. To test for differences between groups, we constructed a linear regression model with the continuous measure of memory awareness as the outcome and indicators for MCI and dementia. This and all subsequent models were adjusted for the potentially confounding effects of age, education, sex, and race/ethnicity. On average, memory awareness was 0.37-unit lower in MCI (SE = 0.04, p<0.001) and 1.04-unit lower in dementia (SE=0.06, p<0.001) compared to the no cognitive impairment group.

Figure 1.

Figure 1.

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Distribution of memory awareness in persons with no cognitive impairment, mild cognitive impairment, or dementia.

Because awareness has often been treated as a categorical variable in prior research, we defined it as an awareness score at or below cutpoints placed at the 15th, 20th, and 25th percentiles in the population. Relative to the no cognitive impairment reference group, the odds of being unaware of memory impairment in MCI were 7-to 9-fold as high and the odds in dementia were 67-to 91fold as high (Table 2). At the 20th percentile cutpoint, which yielded the largest odds ratios, unawareness of memory impairment was present in 24.4% of those with MCI and 76.2% of those with dementia.

Table 2.

Associations of diagnosis with anosognosia defined by awareness scores below different thresholds

Awareness threshold Diagnostic group (% with anosognosia) Odds ratio 95% CI
15th percentile No cognitive impairment (1.9%)
MCI (15.2%) 7.6 44.7,126.3
Dementia (67.3%) 75.2 4.6,12.7
20th percentile No cognitive impairment (3.4%)
MCI (24.4%) 9.1 6.0, 13.8
Dementia (76.2%) 90.8 57.1,144.6
25th percentile No cognitive impairment (5.7%)
MCI (33.1%) 7.0 5.1, 9.8
Dementia (83.1%) 67.0 44.6,100.7
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*Note. Estimated from separate logistic regression models adjusted for age, education, sex, and race/ethnicity. MCI, mild cognitive impairment.

Risk Factors for Memory Unawareness

To determine whether the variable memory awareness observed within diagnostic groups was associated with demographic factors, we repeated the initial model with terms added for the interactions of MCI and dementia with each demographic variable. As shown in Table 3, race/ethnicity interacted with both MCI (estimate = 0.305, SE=0.084, p<0.001) and dementia (estimate=0.370, SE=0.121, p=0.003). Figure 2, which is based on this analysis, shows that memory awareness was more preserved in Black persons with MCI and dementia compared to White persons with these conditions.

Table 3.

Associations of diagnosis, demographic variables, and their interactions with memory awareness

Model Term Estimate SE p-value
Age at diagnosis -0.020 0.004 <0.001
Education 0.040 0.006 <0.001
Sex -0.173 0.034 <0.001
Race/ethnicity -0.149 0.034 <0.001
Time to diagnosis 0.002 0.004 0.700
MCI -0.563 0.087 <0.001
Dementia -1.389 0.117 <0.001
MCI x age 0.002 0.005 0.51
MCI x education -0.007 0.010 0.12
MCI x sex -0.007 0.067 0.915
MCI x race/ethnicity 0.305 0.084 <0.001
Dementia x age 0.012 0.009 0.202
Dementia x education -0.019 0.015 0.220
Dementia x sex 0.248 0.130 0.059
Dementia x race/ethnicity 0.370 0.121 0.003
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*Note. Estimated from a linear regression model. SE, standard error; MCI, mild cognitive impairment.

Figure 2.

Figure 2.

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Level of memory awareness in White (gray) and Black (black) persons with no cognitive impairment, mild cognitive impairment, or dementia.

Awareness of memory dysfunction in dementia is hypothesized to partly reflect psychosocial factors (Clare,Nelis, Martyr, Roberts, et al., 2012). To test this hypothesis, we repeated the initial linear regression model with terms added for 2 key personality variables, neuroticism and extraversion, and their interactions with MCI and dementia. Importantly, personality was assessed when participants were dementia free, a mean of more than 6 years before the clinical evaluation (Table 1). As shown in Table 4, there was no main effect for neuroticism (estimate=0.010, SE=0.008, p=0.205) or extraversion (estimate=−0.013, SE=0.008, p=0.113), but there was an interaction of neuroticism with dementia such that a higher premorbid level of the trait was associated with better memory awareness in dementia (Table 4). In a subsequent analysis, there was no evidence that the association of premorbid personality with memory awareness in MCI or AD varied by race/ethnicity.

Table 4.

Associations of neuroticism and extraversion with memory awareness in diagnostic groups

Model Term Estimate SE p-value
Age at diagnosis -0.020 0.003 <0.001
Education 0.039 0.005 <0.001
Sex -0.164 0.027 <0.001
Race/ethnicity -0.036 0.032 0.264
Time to diagnosis 0.003 0.005 0.509
MCI -0.420 0.047 <0.001
Dementia -1.116 0.073 <0.001
Neuroticism 0.010 0.008 0.205
Extraversion -0.013 0.008 0.113
MCI x neuroticism -0.000 0.024 0.998
MCI x extraversion -0.043 0.024 0.076
Dementia x neuroticism -0.057 0.022 0.009
Dementia x extraversion -0.023 0.021 0.268
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*Note. Estimated from a linear regression model. SE, standard error; MCI, mild cognitive impairment.

Consequences of Memory Unawareness

To assess the consequences of memory unawareness in MCI and dementia, we constructed proportional hazards models with time to death as the outcome. In the initial model, MCI (hazard ratio [HR]: 1.37; 95% confidence interval [CI]: 1.07, 1.75), dementia (HR: 1.97; 95% CI: 1.20, 3.24) and lower level of memory awareness (HR: 0.68; 95% CI: 0.52, 0.89) were each associated with increased mortality. However, in a subsequent model, there was no interaction of memory awareness with either MCI (estimate = −0.09, SE=0.31, p=0.784) or dementia (estimate = −0.26, SE=0.28, p=0.353).

A total of 1,343 participants had follow-up cognitive data, including 772 with no cognitive impairment, 428 with MCI, and 143 with dementia. To test whether memory unawareness in MCI and dementia was associated with accelerated cognitive decline, we constructed a mixedeffects model with a measure of global cognition as the outcome (mean at time of clinical evaluation = 0.30, SD = 0.58). In this analysis, there were no 3-way interactions of dementia by memory awareness by time (estimate = 0.034, SE = 0.023, p=0.868) but there was a marginal MCI by memory awareness by time interaction (estimate =−0.033, SE = 0.016, p = 0.036), indicating that higher level of memory awareness was associated with slower rate of cognitive decline in MCI.

Discussion

A population-based sample of more than 1,800 older persons had a uniform evaluation that included assessment of awareness of memory function and clinical classification of MCI and dementia. Awareness of memory impairment was reduced in both conditions. With impairment defined as memory awareness at or below the 20th percentile of the population, approximately 25% were affected in MCI and 75% in dementia. The results suggest that unawareness of memory impairment is a nearly inevitable consequence of dementia.

Estimates of the prevalence of memory unawareness in MCI and dementia have varied widely.For example, some studies have found virtually no evidence of unawareness in MCI (Farias, Mungas, & Jagust, 2005; Orfei et al., 2010) while others have found equivalent levels of unawareness in MCI and dementia (Vogel, Hasselbalch, Gade, Ziebell, & Waldermar, 2005). Several factors are likely contributing to this variability. First, not only is awareness assessed in different ways but there is little consensus on how much unawareness constitutes impairment. Second, with few exceptions (Mograbi et al., 2012; Mograbi et al., 2015), research has been conducted on selected groups in medical settings, possibly introducing bias and making it difficult to identify comparable controls. The present study confronted these issues by avoiding informant report in measuring awareness, employing a variety of cutoff scores to define unawareness, and using cases and controls sampled from a defined community-based population. The results clearly demonstrate that awareness is reduced in MCI, with 15% to 33% exhibiting unawareness depending on the cutoff score used, and further reduced in dementia, with 67% to 83% meeting criteria for unawareness.

Most prior research on memory awareness has been conducted on White persons. An unexpected finding in this community population was that unawareness of memory impairment in both MCI and dementia was less severe in Black persons than White persons. The basis of this finding is uncertain. The incidence of dementia is higher in Black persons than White persons (Tang, et al., 2001; Chin, Negash, & Hamilton, 2011; Yaffe et al., 2013; Weuve et al., 2017), but there are minimal differences in rate of cognitive decline (Masel & Peck, 2009; Wilson, Capuano, et al., 2015; Weuve et al., 2017). This suggests that, on average, Black persons with dementia have experienced less cognitive decline than White persons with dementia which might help account for the better agreement between subjective and objective memory measures in Black persons than White persons. Further research on memory awareness in racial/ethnic minorities is needed.

Premorbid personality has been hypothesized to contribute to awareness of impairment in early stage dementia (Clare et al., 2012), but research to date has been inconclusive (Seiffer et al., 2005; Gilleen et al., 2012; Mograbi, Brown, et al., 2014; Studer, Donati, Popp, & von Gunten, 2014), possibly in part because measuring premorbid personality retrospectively through proxies likely substantially increases error. A novel feature of the present study is that aspects of personality were assessed a mean of more than 6 years prior to dementia onset. Extraversion was not related to memory awareness in MCI or dementia, but we did find that higher premorbid level of neuroticism was associated with higher level of memory awareness in dementia. Higher neuroticism has been associated with lower subjective memory appraisal in persons without dementia (Memena, Speelman, Foster, & Kaczmarek, 2013; Rowell, Green, Teachman, & Salthouse, 2016). Because high premorbid neuroticism is an unlikely indicator of relative preservation of episodic memory in dementia (Wilson et al., 2004), it seems more likely that the observed association of higher neuroticism with better awareness of memory impairment in this study, and with clearer appreciation of cognitive task difficulty in prior research (Mograbi, Brown, et al., 2014), reflects the persistence of this premorbid tendency to underestimate memory function as dementia develops.

Previous research has linked unawareness of impairment to adverse consequences in MCI and dementia. These consequences include increased caregiver burden in MCI (Kelleher, Tolea, & Galvin, 2016) and dementia (Seltzer, Vasterling, Yoder, & Thompson, 1997; Conde-Sala et al., 2013; Turró-Garriga, et al., 2013; Perales, Turró-Garriga, Gascon-Bryan, Rene-Ramierz, & Conde-Sala, 2016), increased depression and anxiety in dementia (Perales et al., 2006), and less benefit from rehabilitation in dementia (Fernández-Calvo, Contador, Ramus, Olazaran, Mograbi, & Morris, 2015). However, these studies either had cross-sectional designs (Kelleher et al., 2016; Seltzer et al., 1997; Conde-Sala et al., 2013; Turró-Garriga et al., 2013; Starkstein, Jourge, Mizrahi, Adrian, & Robinson, 2007) or relatively brief (≤ 2 years) follow-up (Perales et al., 2016), making results difficult to interpret. In addition, informant report was used in assessing awareness, the outcome, or both, further complicating findings. By way of contrast, with a mean of 6.2 years of observation of vital status and cognitive decline, awareness in the present study showed no association with mortality and a marginal association with cognitive decline. Further research on these and other consequences of unawareness of memory impairment is needed.

This study has notable strengths. Persons with and without cognitive impairment were sampled from the same population, making it likely that they are comparable. Awareness was assessed without reliance on informant report using a previously established method. The longitudinal design allowed assessment of potential risk factors before the diagnosis of dementia and potential consequences following the diagnosis. Important limitations are that awareness was only assessed in one domain at a single time point, and it is uncertain how best to convert a continuous measure of memory awareness into a dichotomous one.

Public significance:

Although it is recognized that some persons with dementia are unaware of their impairments, it remains uncertain how often this happens or whether it impacts disease course. In a longitudinal study of older community residents, most persons with dementia had diminished awareness of their memory impairment, but awareness did not predict subsequent morbidity or mortality, suggesting that declining awareness of dysfunction is part of the natural history of dementia.

Acknowledgments

This research was supported by National Institute on Health (R01AG1101, P30AG10161, RF1AG22018). The funding organizations had no role in the design or conduct of the study; collection, management, analysis, or interpretation of the data; or preparation, review, or approval of the manuscript.

The authors thank the residents of Morgan Park, Washington Heights, and Beverly who participated in the Chicago Health and Aging Project; Mr. Ann Marie Lane for community development and oversight of project coordination, Ms. Michelle Bos, Ms. Holly Hadden, Mr. Flavio LaMorticella, and Ms. Jennifer Tarpey for study coordination; and the staff of the Rush Institute for Healthy Aging.

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