The Association Between Subjective Mental Impairment and Objective Cognitive Performance in Non-Demented,Very Mild and Mild Demented Individuals

Abstract

Objectives

Explore associations between subjective mental impairment, objective cognitive performance, and subsequent decline in older individuals with different cognitive statuses in Taiwan.

Methods

Use self-reported questionnaire and cognitive abilities screening instrument to assess subjective and objective cognitive function. Categorize participants as reporters or non-reporters based on subjective reports. Conduct t-tests and regression analysis.

Results

206 participants were assessed: 99 cognitively intact (CI), 44 very mild dementia, and 63 mild dementia. In the CI group, reporters in memory, orientation, daily life, community affairs, and judgement domains performed worse than non-reporters. In very mild dementia group, reporters in memory and personality domains performed better than non-reporters. No association found between subjective reports and 1-year cognitive decline in dementia groups.

Conclusion

Association between subjective impairment and objective performance differs in CI and very mild dementia groups. Subjective reports do not predict 1-year cognitive decline in dementia patients. Longer follow-up studies needed.

Keywords

Alzheimer’s disease insight objective cognitive impairments subjective mental reports very mild dementia

Significance Statement

1. This is the first study to explore the potential association between subjective mental reports and objective performance for individuals with different cognitive statuses in Taiwan.

2. Subjects with very mild and mild stage of dementia showed higher frequencies of reports in the memory, orientation and ADL domains. Reporters in the memory, orientation, ADL, community affairs and judgement domains had consistently lower performance scores in the CI group. While, in the very mild dementia group, reporters in the memory and personality domains exhibited better performance compared with non-reporters.

3. No association was noted between subjective mental reports and objective performance in the mild dementia group, or between subjective mental reports and subsequent cognitive decline after 1 year.

Introduction

Many adults report an increasing number of memory and other cognitive difficulties as they grow older.¹ Some previous studies have reported that memory reports are associated with depressive symptoms rather than objective cognitive performance.^2-4 However, in other study, subjective memory reports were associated with poorer objective memory performance even after controlling for the effect of depression.⁵ Therefore, whether subjective reports can be considered a reliable indicator of current impairment or the risk of future cognitive decline, remains unknown. If subjective reports are actually associated with cognitive decline, they should not be ignored. In addition, most of these previous studies focused on memory reports, other cognitive or mental domains were less addressed. It remains questionable which cognitive or mental reports increasingly correlate with objective performance.

Differences of associations between subjective reports and objective performance are expected in different stages of cognitive impairment due to dementia. An impaired awareness of cognitive deficits among patients with dementia, or a lack of insight, is common, especially in later stages of the disease process.^6-8 Impaired insight in Alzheimer’s disease (AD) has been associated with frontal lobe functioning, particularly the right lateral frontal area of the brain.⁹ Impairment of insight increased with dementia severity.¹⁰ Studies about the awareness and the association of subjective complaint with actual cognitive performance in AD patients at a milder disease stage, mild cognitive impairment (MCI) or mild AD, have yielded inconsistent results.^11-13 While MCI is heterogeneous, not all MCI individuals have AD.¹⁴ By focusing on intraindividual changes as determined by a Clinical Dementia Rating (CDR) score of .5, AD can be identified at very mild stage.^15,16

In the present study, we aimed to examine 1) the frequency of subjective mental reports in cognitively intact (CI, CDR = 0), very mild dementia (CDR = .5), and mild dementia (CDR = 1) groups of AD Taiwanese patients, 2) the association between different subjective mental reports and actual cognitive performance in different cognitive status and 3) its association with subsequent cognitive decline in the dementia groups. The CDR was used to differentiate subjects with different levels of cognitive function.

Materials and Methods

Recruitment of Participants

Participants over the age of 65 years with intact cognition, very mild dementia, or mild dementia due to AD were recruited from the neurological outpatient department of Kaohsiung Municipal Ta-Tung Hospital located in Southern Taiwan. The older participants and their relatives were informed of the details of study. The Kaohsiung Medical University Hospital Institutional Review Board [KMUHIRB-SV(II)-20170021] approved the study protocol and the participants provided written informed consent prior to their inclusion. Healthy individuals without dementia as determined by a CDR score of 0 and an instrument of ascertainment of dementia 8 (AD8) score of <2 were recruited in the CI group. AD8 is a brief tool used to screen for dementia that was developed at Washington University in St. Louis and is capable of screening for extremely mild dementia in the general population. If the AD8 score is greater than or equal to 2, the person is suspected of having dementia, including extremely mild dementia.¹⁷ The CI older individuals recruited in our study were volunteers selected from outpatients at the neurology clinic. Most of them were relatives or partners of the patients visiting as outpatients at the neurology clinic. Stable AD patients with CDR scores of .5 and 1 who had been receiving acetylcholinesterase inhibitors for at least 12 months, were recruited as the very mild and mild dementia groups, respectively. The diagnosis of AD was based on the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer’s Disease and Related Disorders Association (NINCDS-ADRDA) criteria.¹⁸ The exclusion criteria were a CDR of 2 or above (not the aim of our study), a known history of other neurodegenerative disorders and major psychotic disorders.

Assessment

Assessment of Subjective Mental Reports

In our study, 2 independent clinical psychologists interviewed and tested the individuals. Subjective mental reports followed by objective cognitive performance were assessed by the same psychologists. The self-reported Questionnaire for History of Mental Activity (QHMA), expanded from the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD),¹⁹ was used to assess subjective mental reports and was administered before the psychologists performed any psychometric procedures. The QHMA includes questions about memory, language, personality, orientation to time and space, activities of daily living (ADL), community affairs and judgement. For example, in memory domain, the subjects were asked questions about if any impairments in the area of everyday memory, such as: “Do you have trouble remembering things that have happened recently?’’ “Do you have trouble recalling conversations a few days or few hours later?’’ “Do you always ask the same questions?’’ “Do you leave the stove on?’’ Answers were coded in 3 categories: no; yes; not applicable. According to these answers, the psychologists assessed and divided the participants into 2 groups as either reporters or non-reporters, with respect to their reports of impairments or changes in each domain.

Assessment of Objective Cognitive Performance

The Cognitive Abilities Screening Instrument (CASI) was used to objectively assess overall cognitive function. The CASI has a score range of 0 to 100 and provides a quantitative assessment of attention, concentration, orientation, short-term memory, long-term memory, language abilities, visual construction, list-generating fluency, abstraction, and judgment.²⁰ The typical administration time for the CASI is 15 to 20 minutes. Pilot testing has demonstrated its cross-cultural applicability and its usefulness in screening for dementia, in monitoring disease progression, and in providing profiles of cognitive impairment.²⁰ The CASI assessment was performed for all participants and was repeated 1 year later in the dementia group by 2 experienced psychologists. The cognitive change was defined as the second CASI score minus the first score.

Statistical Analysis

Data was presented as the mean ± standard deviation (SD) or proportion. The chi-squared test was used to compare the frequency of subjective mental reports in CI, very mild dementia, and mild dementia groups, and the one-way analysis of variance (ANOVA) test were used for comparison of demographic characteristic and baseline CASI in these groups. Reporters and non-reporters in each domain were compared according to their objective cognitive performance by Student’s t-test. Multivariate regression models were conducted to evaluate the independent relationships between baseline subjective mental reports and objective cognitive changes. This model was adjusted for age, gender, educational level and the 1st CASI score. Analyses were performed using SPSS 26.0 (SPSS Inc., Chicago, IL, USA). A two-tailed P-value of <.05 was considered to indicate a statistically significant difference.

Results

Demographic Characteristic and Subjective Mental Reports of Participants with Different Cognitive Statuses

A total of 206 subjects completed the assessment and 99 were CI (CDR = 0); 44 were classified as having very mild dementia (CDR = .5), and 63 having mild dementia (CDR = 1). The mean age in years was 71.9 ± 6.9, 75.5 ± 7.6 and 79.0 ± 6.9 in the CI, very mild, and mild dementia groups, respectively. The mean educational level in years was 9.8 ± 4.2, 9.8 ± 4.8 and 6.4 ± 5.0, respectively. The mean CASI score was 84.2 ± 9.1, 78.3 ± 10.4 and 55.1 ± 12.9, respectively. An increasing frequency of reported impairments in mental activity with increasing CDR scores. The mean reported domain numbers were 1.9 ± 1.9, 2.5 ± 1.9, and 2.6 ± 1.8, respectively (P = .027). Subjects with very mild and mild stage of dementia showed higher frequencies of reports in the memory, orientation and ADL domains (P = .014, .001 and .008, respectively) (Table 1).

Table 1.

Demographic Characteristics and Subjective Mental Reports of Participants with Different Cognitive Statuses.

	CI (N = 99)	Very mild dementia (N = 44)	Mild dementia (N = 63)	P value
Age (years)	71.9 ± 6.9	75.5 ± 7.6	79.0 ± 6.9	<.001*
Gender, female (%)	66 (66.7)	16 (36.4)	45 (71.4)	<.001*
Education (years)	9.8 ± 4.2	9.8 ± 4.8	6.4 ± 5.0	<.001*
CASI	84.2 ± 9.1	78.3 ± 10.4	55.1 ± 12.9	<.001*
Domains of subjective mental reports	1.9 ± 1.9	2.5 ± 1.9	2.6 ± 1.8	.027*
Memory (+)	60 (60.6)	33 (75.0)	46 (73.0)	.014*
Language (+)	10 (10.1)	10 (22.7)	10 (15.9)	.214
Personality (+)	20 (20.2)	4 (9.1)	8 (12.7)	.115
Orientation (+)	22 (22.2)	19 (43.2)	32 (50.8)	.001*
ADL (+)	31 (31.3)	27 (61.4)	30 (47.6)	.008*
Community Affairs (+)	23 (23.2)	9 (20.5)	23 (36.5)	.054
Judgement (+)	19 (19.2)	8 (18.2)	17 (27.0)	.110

Data are shown as the mean ± SD for quantitative variables and n (%) for qualitative variables.

P value for CI, very mild dementia vs mild dementia group using analysis of variance (ANOVA) test or Chi-squared test.

*P < .05, statistically significant.

(+): reported impairments or changes.

CI, Cognitively intact; CASI: Cognitive Assessment Screening Instrument; ADL: Activity of Daily Living.

Association Between Subjective Mental Reports and Objective Cognitive Performance in Different Cognitive Statuses

With regard to the association between subjective mental reports and objective cognitive performance, there were significant differences between the non-reporters and reporters in memory, orientation, ADL, community affairs and judgement domains with respect to the CASI total score in the CI group. The reporters had significantly lower scores compared with the non-reporters (P = .027, <.001, <.001, .018 and <.001 in memory, orientation, ADL, community affairs and judgement domain, respectively). While, for participants with very mild dementia, the memory and personality domain reporters had significantly higher total CASI scores than the non-reporters (P = .006 and .016 in memory and personality domain, respectively). There was no association between subjective mental reports and objective cognitive performance in the mild dementia group (Table 2).

Table 2.

Association Between Subjective Mental Reports and Objective Cognitive Performance in Different Cognitive Statuses.

		CASI total score
Domains of subjective mental reports		CI (N = 99)		Vert mild dementia (N = 44)		Mild dementia (N = 63)
Memory	(-)	87.1 ± 8.9	P = .027*	71.1 ± 8.2	P = .006*	49.9 ± 13.1	P = .052
Memory	(+)	82.2 ± 9.3	P = .027*	80.9 ± 9.1	P = .006*	57.0 ± 12.5	P = .052
Language	(-)	84.6 ± 9.0	P = .335	77.6 ± 10.4	P = .149	54.0 ± 13.1	P = .140
Language	(+)	81.6 ± 10.6	P = .335	82.8 ± 7.0	P = .149	60.6 ± 10.6	P = .140
Personality	(-)	85.1 ± 8.8	P = .137	77.7 ± 9.5	P = .016*	54.6 ± 13.3	P = .477
Personality	(+)	81.7 ± 10.2	P = .137	90.0 ± 6.1	P = .016*	58.1 ± 10.1	P = .477
Orientation	(-)	86.5 ± 8.2	P < .001*	77.1 ± 9.7	P = .387	55.8 ± 12.5	P = .067
Orientation	(+)	76.9 ± 8.8	P < .001*	79.9 ± 10.6	P = .387	54.4 ± 13.6	P = .067
ADL	(-)	87.5 ± 7.4	P < .001*	76.6 ± 10.0	P = .402	55.8 ± 11.0	P = .845
ADL	(+)	77.6 ± 9.1	P < .001*	79.3 ± 10.7	P = .402	55.2 ± 14.9	P = .845
Community Affairs	(-)	85.6 ± 8.8	P = .018*	77.4 ± 11.0	P = .139	55.6 ± 10.4	P = .691
Community Affairs	(+)	80.3 ± 10.2	P = .018*	81.6 ± 5.6	P = .139	54.1 ± 16.6	P = .691
Judgement	(-)	86.6 ± 8.1	P < .001*	77.6 ± 11.0	P = .485	55.1 ± 13.7	P = .856
Judgement	(+)	75.8 ± 9.0	P < .001*	80.5 ± 8.0	P = .485	55.8 ± 10.7	P = .856

Objective cognitive performance was assessed by CASI total score.

Data are shown as the mean ± SD for quantitative variables.

P value for (+) vs (-) using the Student’s t-test. *, P < .05, statistically significant.

(+): reporter, reported impairments or changes; (-): non-reporter, did not report impairments or changes.

CI, Cognitively intact; CASI: Cognitive Assessment Screening Instrument; ADL: Activity of Daily Living.

Association Between Subjective Mental Reports and Objective Cognitive Change in Patients with Very Mild and Mild Dementia

In participants with very mild dementia and mild dementia, the associations between baseline subjective mental reports and objective cognitive change over 1 year were assessed. After adjusting for age, gender, education level and 1st CASI score, no association was noted between baseline subjective mental reports and subsequent cognitive decline (Table 3).

Table 3.

Association Between Subjective Mental Reports and Objective Cognitive Change in Patients with Very Mild and Mild Dementia.

Domains of subjective mental reports	Very mild dementia		Mild dementia
Memory (+)	β = .153	P = .346	β = .071	P = .651
Language (+)	β = .111	P = .584	β = .215	P = .147
Personality (+)	β = .181	P = .365	β = .002	P = .987
Orientation (+)	β = −.138	P = .388	β = .105	P = .491
ADL (+)	β = .029	P = .858	β = −.089	P = .560
Community Affairs (+)	β = −.183	P = .271	β = −.093	P = .528
Judgement (+)	β = .139	P = .425	β = −.195	P = .188

Objective cognitive change was assessed by ∆CASI over 1 year; ΔCASI = 2nd CASI – 1st CASI.

The independent relationships between subjective mental reports and objective cognitive change were evaluated by multivariate regression model and adjusted for age, gender, educational level and 1st CASI. *, P < .05, statistically significant.

(+): reported impairments or changes.

CASI: Cognitive Assessment Screening Instrument; ADL: Activity of Daily Living.

Discussion

In the current study, we investigated the potential association between different subjective mental reports, objective cognitive function and subsequent cognitive decline in the older individuals with different cognitive statuses. Subjects with very mild and mild stage of dementia showed higher frequencies of reports in the memory, orientation and ADL domains. Reporters in the memory, orientation, ADL, community affairs and judgement domains had consistently lower performance scores in the CI group. While, in the very mild dementia group, reporters in the memory and personality domains had better performance compared with non-reporters. No association was noted between subjective mental reports and objective performance in the mild dementia group, or between subjective mental reports and subsequent cognitive decline after 1 year. To the best of our knowledge, this is the first study to explore the potential association between subjective mental reports and objective performance for individuals with different cognitive statuses in Taiwan.

In our study, subjects with very mild and mild stage of dementia showed higher frequencies of reports in the memory, orientation and ADL domains, indicating that they still retain the awareness to detect their mental change. As memory and orientation are usually early signs of cognitive impairment in dementia which can interfere even subtly with everyday functioning,²¹ this observation helps to validate the usefulness of these reports in differentiating dementia from intact cognition.

In our study, subjective mental reports in memory, orientation, ADL, community affairs and judgement domains were associated with poor objective performance in the CI group. Reporters in these domains had significantly lower performance scores compared with non-reporters, which was different to some community studies where memory reports and performance were poorly correlated in the normal group.^4,22 These different outcomes may be related to the different sources of subject recruitment between the studies.^4,23 Subjects who are recruited from a clinical population may reflect individuals who have some cognitive problems, or who are more concerned about their cognitive problems. In contrast, the reports of a sample of community subjects, may be less significant. In our study, most of the participants in the CI group were relatives or partners of the patients visiting as outpatients at the memory clinic. They therefore might be more familiar with the symptoms of cognitive decline and more concerned about their own mental activity.

Contrary to the CI group, reporters in the memory and personality domains performed better than non-reporters in the very mild dementia group. In this stage, those with more cognitive ability might be more aware of their own deterioration, even if this difference is subtle. Therefore, reporters had better cognitive performance. Subjects with very mild dementia may have better judgment and an increased ability to estimate their own mental capacity. While in more severe cognitive impairment stages, patients may lose the ability to introspect and evaluate their own cognitive problems.

Different from most of the previous studies, we evaluated mental reports not only in the memory domain but also in other domains, and tried to explore which domains were more correlated with objective performance. In the CI group, reports concerning memory, orientation, ADL, community affairs and judgement domains correlated with objective performance. As previously discussed, memory and orientation are usually early signs of cognitive impairment and can interfere with ADL and community functioning. In the very mild dementia group, reports concerning memory as well as personality, were more correlated with objective performance. Changes in personality may be an early sign of dementia. People with dementia commonly exhibit changes in personality that sometimes precede other early clinical manifestations, such as memory and cognition problems.²⁴

In the current study, subjective mental reports did not predict subsequent cognitive decline in the dementia group. In a study conducted in individuals aged 70 years and older without cognitive impairment at baseline, a significant association between subjective cognitive decline and decline in cognitive performance was noted during the 5 years follow-up.²⁵ In a meta-analysis, older people with subjective memory complaints but no objective deficits were twice as likely to develop dementia compared with individuals without subjective memory complaints.²⁶ This means that older people may notice cognitive deterioration at a time when currently available tests are unable to verify any change, but decreasing objective cognitive performance can be measured at a later time. However, the study populations in these studies were nondementia subjects, which is different to our dementia population. In the very mild and mild stages of dementia, cognitive function did not decline faster in those who still retained the ability to evaluate their mental activity, even though they reported impairments or changes of mental activity. This hypothesis should be proven in a longer follow up study.

There are some limitations to the present study. First, informant reports were not determined in this study. As the primary objective was to evaluate the significance of subjective reports, it was decided that only subjective reports would be evaluated. Another limitation was that we did not include depression and anxiety as potential statistical confounders. As our primary aim was to evaluate whether there was a difference between the cognitive performance of reporters and non-reporters, a t-test was used. In addition, patients with very mild and mild dementia in the current study had a very low percentage of depression and anxiety. Only 6 patients (5.6%) had depression symptoms and only 4 patients (3.7%) had anxiety symptoms. Lastly, the follow-up duration may be not sufficient for assessing subsequent cognitive decline. A longer follow-up study should be conducted in the future to confirm the findings of the current study.

In conclusion, the present study demonstrated that very mild and mild dementia patients still retained the awareness to detect their own mental decline. The association between subjective mental reports and objective performance was stronger in CI and very mild dementia individuals compared with mild dementia patients. Subjective mental reports did not predict subsequent cognitive decline during the 1 year follow up in the dementia groups. A longer follow-up time is required in future studies.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This study was supported by the Clinical psychologists and assistant of the Department of Neurology, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung, Taiwan and by Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung, Taiwan, grant No. kmtth-110-027 and partially by Kaohsiung Medical University Research Center Grant (KMU-TC109B03).

ORCID iDs

Ling-Chun Huang

Yuan-Han Yang

Data Availability Statement

The raw supporting the conclusions of this article will be made available by the authors, without undue reservation.

Appendix

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