Mild cognitive impairment: a risk indicator of later dementia, or a preclinical phase of the disease?

Progression from Subjective Cognitive Decline to Mild Cognitive Impairment or Dementia: The Role of Baseline Cognitive Performance

Background: Older adults with subjective cognitive decline (SCD) are at an increased risk of progression to mild cognitive impairment (MCI) or dementia. However, few have examined the specific cognitive tests that are associated with progression. Objective: This study examined performance on 18 neuropsychological tests among participants with SCD who later progressed to MCI or dementia. Methods: We included 131 participants from the Czech Brain Aging Study that had SCD at baseline. They completed a comprehensive neuropsychological battery including cognitive tests from the Uniform Data Set 2.0 enriched by the verbal memory test Rey Auditory Verbal Learning Test (RAVLT) and Rey-Osterrieth Complex Figure Test (ROCFT). Results: Fifty-five participants progressed: 53% to non-amnestic MCI (naMCI), 44% to amnestic MCI (aMCI), and 4% to dementia. Scoring one SD below the mean at baseline on the RAVLT 1 and RAVLT 1–5 was associated with 133% (RAVLT 1; HR: 2.33 [1.50, 3.62]) and 122% (RAVLT 1–5; HR: 2.22 [1.55, 3.16]) greater risk of progression to MCI or dementia over 3.84 years on average. Worse performance on the RAVLT 5, RAVLT 1–5, RAVLT 30, and ROCFT–Recall was associated with progression to aMCI whereas worse performance on the RAVLT 1, TMT B, and Boston Naming Test was associated with progression to naMCI. Conclusion: At baseline, lower verbal memory performance was most strongly associated with progression to aMCI whereas lower executive or language performance was most strongly associated with progression to naMCI.

Verbal and spatial memory spans in mild cognitive impairment

OBJECTIVES

Working memory (WM) for verbal and visual material may be affected early in individuals with mild cognitive impairment (MCI). Verbal and visuospatial span tasks, that is neuropsychological procedures commonly used for the clinical assessment of WM, have been scarcely investigated in these patients. Therefore, this study was aimed at evaluating whether performance on tests of verbal and visual-spatial span (which rely to different extents on distinct components of the WM system) is differently sensitive to the presence of MCI and, in particular, of a preclinical AD condition in patients with MCI.

MATERIALS & METHODS

99 patients with amnesic MCI were given the Digit Span Forward (DSF) and Digit Span Backward (DSB) tests and the Corsi span task (CS) at baseline and were followed up for two years. 32 MCI patients converted to Alzheimer's disease (MCIc), but 67 patients did not deteriorate to meet the criteria for AD (MCIs).

RESULTS

Results showed that although performance on DSF did not differ between groups, performance on DSB and CS and ratio indexes indicative of a performance decline passing from DSF to DSB and from DSF to CS significantly discriminated between a group of matched healthy controls and the overall group of MCI patients. Moreover, the ratio indexes significantly discriminated between MCIc and MCIs individuals.

CONCLUSIONS

These data are consistent with the hypothesis that individuals with MCI, particularly those destined to convert to AD, are affected by reduced central executive resources even though the phonological loop is still functioning normally.

Changes in visual memory in mild cognitive impairment: a longitudinal study with CANTAB

BACKGROUND

Mild cognitive impairment (MCI), as a stage in the cognitive continuum between normal ageing and dementia, is mainly characterized by memory impairment. The aims of this study were to examine CANTAB measures of temporal changes of visual memory in MCI and to evaluate the usefulness of the baseline scores for predicting changes in cognitive status.

METHODS

The study included 201 participants aged over 50 years with subjective cognitive complaints. Visual memory was assessed with four CANTAB tests [paired associates learning (PAL), delayed matching to sample (DMS), pattern recognition memory (PRM) and spatial span (SSP)] administered at baseline and on two further occasions, with a follow-up interval of 18-24 months. Participants were divided into three groups according to the change in their cognitive status: participants with subjective cognitive complaints who remained stable, MCI participants who remained stable (MCI-Stable) and MCI participants whose cognitive deterioration continued (MCI-Worsened). Linear mixed models were used to model longitudinal changes, with evaluation time as a fixed variable, and multinomial regression models were used to predict changes in cognitive status.

RESULTS

Isolated significant effects were obtained for age and group with all CANTAB tests used. Interactions between evaluation time and group were identified in the PAL and DMS tests, indicating different temporal patterns depending on the changes in cognitive status. Regression models also indicated that CANTAB scores were good predictors of changes in cognitive status.

CONCLUSIONS

Decline in visual memory measured by PAL and DMS tests can successfully distinguish different types of MCI, and considered together PAL, DMS, PRM and SSP can predict changes in cognitive status.

Characteristics of Individuals Who Converted to Dementia during a 5-Year Follow-Up

INTRODUCTION

Early diagnosis of dementia is important; however, the diagnostic criteria for the preclinical stage of dementia, including biomarkers and pathophysiological markers, are not suitable for application in patients in real-world clinical settings. One potential noninvasive method to predict the risk of dementia conversion is the neuropsychological test. Therefore, in this study, we examined the results of various assessments, such as comprehensive neuropsychological tests, and the daily function of participants who were evaluated periodically for 5 years.

METHODS

All participants were outpatients or inpatients with subjective cognitive complaints, who visited a local university hospital for neuropsychiatric evaluation, between January 2011 and January 2019. Of a total of 1,652 subjects who underwent initial screening during this period, 107 were nondemented individuals. These participants underwent periodic comprehensive cognitive tests for up to 5 years. Survival and factors affecting dementia conversion were analyzed using the time-dependent Cox regression analysis. Assessment items included demographic information, including age, sex, and education; 5 cognitive domains of a comprehensive neuropsychological test including memory, language, attention, visuospatial functions, and frontal (executive) function; Barthel's activities of daily living; the mini-mental state examination findings; and clinical dementia rating (CDR) scores.

RESULTS

This study included 61 participants (21 women and 40 men) who developed dementia during the study period. Verification of the cognitive variables affecting dementia conversion revealed that better memory was associated with a lower risk of conversion (hazard ratio [HR] = 0.614, p = 0.005) and higher attention was associated with a higher risk of conversion (HR = 1.602, p = 0.023). In the analysis of the subscales of the CDR, a higher community affairs score (i.e., less social activities) was associated with a higher risk of conversion (HR = 10.814, p = 0.028).

CONCLUSION

Individuals with prominent memory decline or problems with social activities should be carefully observed for dementia conversion. Cognitive intervention techniques for cognitive stimulation, such as social and leisure activities, as well as cognitive training need to be actively used for patients in whom dementia is a concern.

A Normative Study of the Full Version of Story Memory in the Korean-Mini Mental State Examination, 2nd Edition: Expanded Version (K-MMSE-2: EV)

BACKGROUND AND PURPOSE

The Mini Mental State Examination, 2nd edition: Expanded version (MMSE-2: EV) involves an immediate recall (IR) of story memory (SM). A full version of SM has been developed and standardized; it includes delayed recall (DR) and recognition tests in addition to IR to increase its clinical utility as an independent story recall test. This study was conducted to provide norms for the full version of SM in the Korean version of MMSE-2: EV for clinical use.

METHODS

A total of 1,168 participants (496 males and 672 females) were included in the study. The ages ranged from 19 to 90 years, and the education level ranged from illiterate to post-graduate. Regression analysis was used to evaluate the relative contributions of demographic variables (age, education, and sex) on the SM measures.

RESULTS

We stratified age into 11 groups, and categorized the education level into 6 groups. It was found that the IR, DR, and recognition scores of SM were affected by age, education level, and sex. We provided corrected means and standard deviations of the IR, DR, and recognition scores of the SM for the demographic variables.

CONCLUSIONS

The results indicate the importance of considering demographic variables in interpreting the full version of SM measures. The normative data we have provided in this study should be useful in clinical and research settings for detecting the impairment in verbal memory.

Neuropsychological predictors of cognitive deterioration in non-demented individuals

Introduction: Previous studies performed neuropsychological tests in non-demented patients, especially those with mild cognitive impairment (MCI), to predict dementia. Few recent studies reported that subjective cognitive decline (SCD) itself predicts dementia conversion. We evaluated certain characteristics and neuropsychological tests to predict cognitive deterioration in non-demented individuals.Methods: This study included 106 participants with subjective cognitive complaints (SCCs) classified as non-demented (90 MCI and 16 SCD). Data were collected at baseline and follow-up, wherein participants completed a comprehensive neuropsychological assessment to assess their cognitive and daily functions.Results: During the follow-up of all participants, 52 converted to dementia, while 54 did not. There were significant differences in age and education years, as well as language, memory, frontal lobe function, and Barthel's Activities of Daily Living Index between the groups. Correlation analysis showed a significant correlation between the deterioration of the Clinical Dementia Rating scores and baseline language, memory, and frontal lobe function scores.Conclusion(s): SCDs consistently worrying about their SCCs and those identified with SCD by their caregivers were prone to cognitive function deterioration over time. Changes in language, memory, and frontal lobe function in neurocognitive tests were significantly different between the dementia converters and non dementia converters group. Particularly, SCD and MCI individuals with significantly poor initial executive function and memory abilities should be closely monitored for future cognitive decline.

Development and Validation of the Full Version of Story Memory in the Korean-Mini Mental State Examination, 2nd Edition: Expanded Version (K-MMSE-2: EV)

Background and Purpose

The Korean version of Story Memory (SM) in the Korean-Mini Mental State Examination, 2nd Edition: Expanded Version (K-MMSE-2: EV) was developed. Based on the SM, we additionally developed a full version of SM including delayed recall (DR) and recognition adding to immediate recall (IR). This study aimed to examine the reliabilities and validities of the newly developed SM in the K-MMSE-2: EV and its full version.

Methods

Ninety-five healthy elderly individuals (HE), 90 patients with amnestic mild cognitive impairment (aMCI), and 53 patients with dementia of the Alzheimer's type (DAT) participated in the study. They were administered the full version of SM with the Seoul Verbal Learning Test-Elderly's version (SVLT-E) and Rey Complex Figure Test (RCFT). In addition, the SM was re-administered to 51 participants after a 5-week interval. Two clinical neuropsychologists independently rated the performance of 50 participants.

Results

The test-retest reliabilities of the IR, DR, and recognition of the SM were statistically significant. The inter-rater reliabilities (Cohen's kappa) were high (0.87–1.00) for all the measures. The IR, DR, and recognition of SM had significant positive correlations with those of the SVLT-E and RCFT. Significant group differences in IR and DR of SM were found among the HE, aMCI, and DAT groups. The recognition scores were significantly different between the aMCI and DAT groups, but not between the HE and aMCI groups.

Conclusions

The newly developed full version of SM in the K-MMSE-2: EV was proven to be a reliable and valid memory measure for clinical use.

Decreased hemodynamic response in inferior frontotemporal regions in elderly with mild cognitive impairment

The verbal fluency task (VFT) is a well-established cognitive marker for mild cognitive impairment (MCI) in the prodromal stage of Alzheimer´s dementia (AD). The behavioral VFT performance of patients allows the prediction of dementia two years later. But effective compensatory mechanism might cover or reduce the predictive value of the VFT. Therefore the aim of this study is to measure the hemodynamic response during VFT in patients with mild cognitive impairment (MCI) to establish the hemodynamic response during the VFT as a screening instrument for the prediction of dementia. One method which allows measuring the hemodynamic response during speech production without severe problems with moving artifacts like in functional magnetic resonance imaging (fMRI) is the functional near-infrared spectroscopy (fNIRS). It is optimal as a screening instrument, as it is easy to apply and without any contraindications. In this study we assessed the hemodynamic response in prefrontal and temporal regions in patients with MCI as well as matched healthy controls with fNIRS. We found a decreased hemodynamic response in the inferior frontotemporal cortex for the MCI group. Our results indicate that a frontotemporal decreased hemodynamic response could serve as a diagnostic biomarker for dementia.

Cognitive and motor functioning in elderly glucocerebrosidase mutation carriers

Mutations in the glucocerebrosidase (GBA) gene are a strong genetic risk factor for the development of Parkinson's disease and dementia with Lewy Bodies. However the penetrance of GBA mutations is low for these diseases in heterozygous carriers. The aim of this study was to examine the relationship between mutation status and cognitive and motor functioning in a sample of community-dwelling older adults. Using linear mixed effects models, we examined the effect of heterozygous mutation status on 736 community-dwelling older adults (≥70 years) without dementia or Parkinson's disease assessed over an average of 6 years, 28 of whom had a single GBA mutation (primarily N370S). Verbal memory was measured using the picture version of the Free and Cued Selective Reminding Test, and carriers showed significantly (p < 0.05) greater decline in verbal memory over time. There was no difference in motor function or any other cognitive domain. Taken together, these results suggest an effect, but an overall limited burden, of harboring a single GBA mutation in aging mutation carriers.

Adding Recognition Discriminability Index to the Delayed Recall Is Useful to Predict Conversion from Mild Cognitive Impairment to Alzheimer's Disease in the Alzheimer's Disease Neuroimaging Initiative

Background: Ongoing research is focusing on the identification of those individuals with mild cognitive impairment (MCI) who are most likely to convert to Alzheimer's disease (AD). We investigated whether recognition memory tasks in combination with delayed recall measure of episodic memory and CSF biomarkers can predict MCI to AD conversion at 24-month follow-up. Methods: A total of 397 amnestic-MCI subjects from Alzheimer's disease Neuroimaging Initiative were included. Logistic regression modeling was done to assess the predictive value of all RAVLT measures, risk factors such as age, sex, education, APOE genotype, and CSF biomarkers for progression to AD. Estimating adjusted odds ratios was used to determine which variables would produce an optimal predictive model, and whether adding tests of interaction between the RAVLT Delayed Recall and recognition measures (traditional score and d-prime) would improve prediction of the conversion from a-MCI to AD. Results: 112 (28.2%) subjects developed dementia and 285 (71.8%) subjects did not. Of the all included variables, CSF Aβ1-42 levels, RAVLT Delayed Recall, and the combination of RAVLT Delayed Recall and d-prime were predictive of progression to AD (χ2 = 38.23, df = 14, p < 0.001). Conclusions: The combination of RAVLT Delayed Recall and d-prime measures may be predictor of conversion from MCI to AD in the ADNI cohort, especially in combination with amyloid biomarkers. A predictive model to help identify individuals at-risk for dementia should include not only traditional episodic memory measures (delayed recall or recognition), but also additional variables (d-prime) that allow the homogenization of the assessment procedures in the diagnosis of MCI.

Accuracy of a Brief Neuropsychological Battery for the Diagnosis of Dementia and Mild Cognitive Impairment: An Analysis of the NEDICES Cohort

Early separation of mild cognitive impairment (MCI) from normal aging and mild cases of dementia remains a challenge, especially in the general population. We aimed to analyze the diagnostic accuracy of a brief neuropsychological battery (BNB) in dementia and MCI cases from the Neurological Disorders in Central Spain (NEDICES) population-based cohort study. We screened 3,891 participants into dementia and non-dementia groups using a two-phase procedure: screening (MMSE-37 and Pfeffer-11) and clinical diagnosis by specialists (DSM-IV criteria). We selected subsequently a subsample of dementia (n = 98), MCI (n = 71), and cognitively healthy (n = 123) participants matched in socio-demographic characteristics. The clinical validity of each test of the BNB was determined by the area under the ROC curve. We determined the best combination of tests to classify individuals into the diagnostic groups by logistic regression analyses. The results indicated that dementia and MCI groups could be best discriminated from the healthy control group on the basis of their scores on the semantic verbal fluency and delayed recall subtests of the BNB. As for discriminating the MCI group from the dementia group, immediate recall tasks (stories and pictures) yielded the highest level of accuracy. Probably the most interesting finding is that the verbal fluency task consistently allowed discrimination among the diagnostic groups. Overall, subtests of the BNB are more accurate in differentiating dementia patients than MCI patients from healthy controls. In this population-based sample, a more fine-grained discrimination that includes MCI patients should follow a systematic subtest-wise analysis and decision.

Assessment of verbal and visuospatial working memory in mild cognitive impairment and Alzheimer's dementia

In addition to episodic memory impairment, working memory may also be compromised in mild cognitive impairment (MCI) or Alzheimer's dementia (AD), but standard verbal and visuospatial span tasks do not always detect impairments.

Working memory binding and episodic memory formation in aging, mild cognitive impairment, and Alzheimer's dementia

INTRODUCTION

Recent studies indicate that in both normal and pathological aging working memory (WM) performance deteriorates, especially when associations have to be maintained. However, most studies typically do not assess the relationship between WM and episodic memory formation. In the present study, we examined WM and episodic memory formation in normal aging and in patients with early Alzheimer's disease (mild cognitive impairment, MCI; and Alzheimer's dementia, AD).

METHOD

In the first study, 26 young adults (mean age 29.6 years) were compared to 18 middle-aged adults (mean age 52.2 years) and 25 older adults (mean age 72.8 years). We used an associative delayed-match-to-sample WM task, which requires participants to maintain two pairs of faces and houses presented on a computer screen for short (3 s) or long (6 s) maintenance intervals. After the WM task, an unexpected subsequent associative memory task was administered (two-alternative forced choice). In the second study, 27 patients with AD and 19 patients with MCI were compared to 25 older controls, using the same paradigm as that in Experiment 1.

RESULTS

Older adults performed worse than both middle-aged and young adults. No effect of delay was observed in the healthy adults, and pairs that were processed during long maintenance intervals were not better remembered in the subsequent memory task. In the MCI and AD patients, longer maintenance intervals hampered the task performance. Also, both patient groups performed significantly worse than controls on the episodic memory task as well as the associative WM task.

CONCLUSIONS

Aging and AD present with a decline in WM binding, a finding that extends similar results in episodic memory. Longer delays in the WM task did not affect episodic memory formation. We conclude that WM deficits are found when WM capacity is exceeded, which may occur during associative processing.

Neuropsychological indicators of preclinical Alzheimer's disease among depressed older adults

Older adults with major depressive disorder (MDD) may also have preclinical Alzheimer's disease (AD). Differential diagnosis is quite challenging due to the overlapping symptoms of MDD and AD. In the current study, we predicted that impaired long-term memory (an area most affected in early AD), but not executive function (an area affected in MDD and AD), would distinguish older depressed patients who developed AD from those who did not. Patients (N = 120) assessed as having MDD but not dementia at baseline were administered tests of cognitive function and followed longitudinally for subsequent diagnosis of AD. Using structural equation modeling we found a latent construct of long-term memory to be associated with AD to a greater extent than executive functioning. Additional analyses to enhance clinical utility of findings indicated that individual tests of episodic memory were most predictive of AD status. Tests of long-term memory can be utilized by the clinician when assessing for preclinical AD among depressed elderly.

Impaired retention is responsible for temporal order memory deficits in mild cognitive impairment

Temporal order memory, or remembering the order of events, is critical for everyday functioning and is difficult for patients with mild cognitive impairment (MCI). It is currently unclear whether these patients have difficulty acquiring and/or retaining such information and whether deficits in these patients are in excess of "normal" age-related declines. Therefore, the current study examined age and disease-related changes in temporal order memory as well as whether memory load played a role in such changes. Young controls (n=25), older controls (n=34), and MCI patients (n=32) completed an experimental task that required the reconstruction of sequences that were 3, 4, or 5 items in length both immediately after presentation (i.e., immediate recall) and again after a 10-min delay (i.e., delayed recall). During the immediate recall phase, there was an effect of age largely due to reduced performance at the two longest span lengths. Older controls and MCI patients only differed during the five span (controls>MCI). During the delayed recall, however, there were significant effects of both age and MCI regardless of span length. In MCI patients, immediate recall was significantly correlated with measures of executive functioning, whereas delayed recall performance was only related to other memory tests. These findings suggest that MCI patients experience initial temporal order memory deficits at the point when information begins to exceed working memory capacity and become dependent on medial temporal lobe functioning. Longer-term deficits are due to an inability to retain information, consistent with the characteristic medial temporal lobe dysfunction in MCI.

Comparison of four verbal memory tests for the diagnosis and predictive value of mild cognitive impairment

Background

Mild cognitive impairment (MCI) is considered to be an early stage of a neurodegenerative disorder, particularly Alzheimer's disease, and the clinical diagnosis requires the objective demonstration of cognitive deficits. The aim of the present study was to evaluate the predictive value of MCI for the conversion to dementia when using four different verbal memory tests (Logical Memory, LM; California Verbal Learning Test, CVLT; Verbal Paired-Associate Learning, VPAL; and Digit Span, DS) in the MCI criteria.

Methods

Participants were consecutive patients with subjective cognitive complaints who performed a comprehensive neuropsychological evaluation and were not demented, observed in a memory clinic setting.

Results

At baseline, 272 non-demented patients reporting subjective cognitive complaints were included. During the follow-up time (3.0 ± 1.9 years), 58 patients converted to dementia and 214 did not. Statistically significant differences between the converters and non-converters were present in LM, VPAL, and CVLT. A multivariate Cox regression analysis combining the four memory tests revealed that only the CVLT test remained significant as a predictor of conversion to dementia. Non-demented patients with cognitive complaints diagnosed as having MCI according to abnormal (<1.5 SD) learning in the CVLT test had a 3.61 higher risk of becoming demented during the follow-up.

Conclusion

The verbal memory assessment using the CVLT should be preferred in the diagnostic criteria of MCI for a more accurate prediction of conversion to dementia.

Level of recall, retrieval speed, and variability on the Cued-Recall Retrieval Speed Task (CRRST) in individuals with amnestic mild cognitive impairment

Individuals with amnestic mild cognitive impairment (aMCI) show deficits on traditional episodic memory tasks and reductions in speed of performance on reaction time tasks. We present results on a novel task, the Cued-Recall Retrieval Speed Task (CRRST), designed to simultaneously measure level and speed of retrieval. A total of 390 older adults (mean age, 80.2 years), learned 16 words based on corresponding categorical cues. In the retrieval phase, we measured accuracy (% correct) and retrieval speed/reaction time (RT; time from cue presentation to voice onset of a correct response) across 6 trials. Compared to healthy elderly adults (HEA, n = 303), those with aMCI (n = 87) exhibited poorer performance in retrieval speed (difference = -0.13; p < .0001) and accuracy on the first trial (difference = -0.19; p < .0001), and their rate of improvement in retrieval speed was slower over subsequent trials. Those with aMCI also had greater within-person variability in processing speed (variance ratio = 1.22; p = .0098) and greater between-person variability in accuracy (variance ratio = 2.08; p = .0001) relative to HEA. Results are discussed in relation to the possibility that computer-based measures of cued-learning and processing speed variability may facilitate early detection of dementia in at-risk older adults.

Assessment of working-memory deficits in patients with mild cognitive impairment and Alzheimer's dementia using Wechsler's Working Memory Index

BACKGROUND AND AIMS

Although episodic memory deficits are a hallmark in mild cognitive impairment (MCI) and Alzheimer's dementia (AD), little attention has been paid so far to the ability to maintain and manipulate information during a brief period of time, i.e. working memory. In this study, we examine verbal working memory in both cognitively unimpaired older people and MCI and AD patients.

METHODS

Seventy- five participants were examined with either no cognitive impairment (n=25), MCI (n=25) or AD (n=25). Working memory was investigated with Wechsler's Working Memory Index tests (Digit Span, Letter-Number Sequencing and Arithmetic).

RESULTS

Both MCI and AD patients performed worse on all three working-memory tests compared with controls, the subtest Letter-Number Sequencing also revealing worse performance in AD compared with MCI patients.

CONCLUSIONS

Workingmemory deficits are already present in MCI patients and worsen in AD patients, suggesting that working memory should be assessed as part of neuropsychological testing.

Differential memory test sensitivity for diagnosing amnestic mild cognitive impairment and predicting conversion to Alzheimer's disease

Episodic memory is the first and most severely affected cognitive domain in Alzheimer's disease (AD), and it is also the key early marker in prodromal stages including amnestic mild cognitive impairment (MCI). The relative ability of memory tests to discriminate between MCI and normal aging has not been well characterized. We compared the classification value of widely used verbal memory tests in distinguishing healthy older adults (n = 51) from those with MCI (n = 38). Univariate logistic regression indicated that the total learning score from the California Verbal Learning Test-II (CVLT-II) ranked highest in terms of distinguishing MCI from normal aging (sensitivity = 90.2; specificity = 84.2). Inclusion of the delayed recall condition of a story memory task (i.e., WMS-III Logical Memory, Story A) enhanced the overall accuracy of classification (sensitivity = 92.2; specificity = 94.7). Combining Logical Memory recognition and CVLT-II long delay best predicted progression from MCI to AD over a 4-year period (accurate classification = 87.5%). Learning across multiple trials may provide the most sensitive index for initial diagnosis of MCI, but inclusion of additional variables may enhance overall accuracy and may represent the optimal strategy for identifying individuals most likely to progress to dementia.