Mild cognitive impairment: clinical features and review of screening instruments

Mild Cognitive Impairment in African Americans Is Associated with Differences in EEG Theta/Beta Ratio

BACKGROUND

Identification of older individuals with increased risk for cognitive decline can contribute not only to personal benefits (e.g., early treatment, evaluation of treatment), but could also benefit clinical trials (e.g., patient selection). We propose that baseline resting-state electroencephalography (rsEEG) could provide markers for early identification of cognitive decline.

OBJECTIVE

To determine whether rsEEG theta/beta ratio (TBR) differed between mild cognitively impaired (MCI) and healthy older adults.

METHODS

We analyzed rsEEG from a sample of 99 (ages 60-90) consensus-diagnosed, community-dwelling older African Americans (58 cognitively typical and 41 MCI). Eyes closed rsEEGs were acquired before and after participants engaged in a visual motion direction discrimination task. rsEEG TBR was calculated for four midline locations and assessed for differences as a function of MCI status. Hemispheric asymmetry of TBR was also analyzed at equidistant lateral electrode sites.

RESULTS

Results showed that MCI participants had a higher TBR than controls (p = 0.04), and that TBR significantly differed across vertex location (p < 0.001) with the highest TBR at parietal site. MCI and cognitively normal controls also differed in hemispheric asymmetries, such that MCI show higher TBR at frontal sites, with TBR greater over right frontal electrodes in the MCI group (p = 0.003) and no asymmetries found in the cognitively normal group. Lastly, we found a significant task aftereffect (post-task compared to pre-task measures) with higher TBR at posterior locations (Oz p = 0.002, Pz p = 0.057).

CONCLUSION

TBR and TBR asymmetries differ between MCI and cognitively normal older adults and may reflect neurodegenerative processes underlying MCI symptoms.

EEG asymmetry and cognitive testing in MCI identification

BACKGROUND

Finding the baseline resting-state EEG markers for early identification of cognitive decline can contribute to the identification of individuals at risk of further change. Potential applications include identifying participants for clinical trials, early treatment, and evaluation of treatment, accessible even from a community setting.

METHODS

Analyses were completed on a sample of 99 (ages 60-90) consensus-diagnosed, community-dwelling African Americans (58 cognitively typical/HC, and 41 mildly cognitively impaired/MCI), who were recruited from the Michigan Alzheimer's Disease Research Center (MADRC) and the Wayne State University Institute of Gerontology. In addition to neuropsychological testing with CogState and Toolbox computerized batteries, resting-state EEGs (rsEEG, eyes closed) were acquired before and after participants were engaged in a visual motion direction discrimination task. rsEEG frontal alpha asymmetry (FAA) and frontal beta asymmetry (FBA) were calculated.

RESULTS

FAA showed no difference across groups for the pre-task resting state. FBA was significantly different between groups, with more asymmetric frontal beta in MCI. Both physiological indices, however, along with computerized neuropsychological tests were significant predictors in logistic regression classification of MCI vs. control participants.

CONCLUSION

rsEEG asymmetries can contribute significantly to successful discrimination of older persons with MCI from those without, over and above cognitive testing, alone.

Brand new norms for a good old test: Northern Italy normative study of MiniMental State Examination

AIM

Mini-Mental State Examination (MMSE) is one of the most used tests for the screening of global cognition in patients with neurological and medical disorders. Norms for the Italian version of the test were published in the 90 s; more recent norms were published in 2020 for Southern Italy only. In the present study, we computed novel adjustment coefficients, equivalent scores and cut-off value for Northern Italy (Lombardia and Veneto) and Italian speaking Switzerland.

METHODS

We recruited 361 healthy young and old (range: 20-95 years) individuals of both sexes (men: 156, women: 205) and from different educational levels (range: 4-22 years). Neuropsychiatric disorders and severe medical conditions were excluded with a questionnaire and cognitive deficits and were ruled out with standardized neuropsychological tests assessing the main cognitive domains. We used a slightly modified version of MMSE: the word 'fiore' was replaced with 'pane' in verbal recalls to reduce the common interference error 'casa, cane, gatto'. The effect of socio-demographic features on performance at MMSE was assessed via multiple linear regression, with test raw score as dependent variable and sex, logarithm of 101-age and square root of schooling as predictors.

RESULTS

Mean raw MMSE score was 28.8 ± 1.7 (range: 23-30). Multiple linear regression showed a significant effect of all socio-demographic variables and reported a value of R2 = 0.26. The new cut off was ≥ 26 /30.

CONCLUSION

We provide here updated norms for a putatively more accurate version of Italian MMSE, produced in a Northern population but potentially valid all over Italy.

EEG alterations during wake and sleep in mild cognitive impairment and Alzheimer's disease

Patients with Alzheimer's disease (AD) undergo a slowing of waking electroencephalographic (EEG) rhythms since prodromal stages, which could be ascribed to poor sleep quality. We examined the relationship between wake and sleep alterations by assessing EEG activity during sleep and (pre-sleep/post-sleep) wakefulness in AD, mild cognitive impairment (MCI) and healthy controls. AD and MCI show high sleep latency and less slow-wave sleep. Reduced sigma activity characterizes non-rapid eye movement (NREM) sleep, reflecting sleep spindles loss. The EEG slowing characterizes REM sleep and wakefulness of AD and MCI, with strong correlations among the two phenomena suggesting common neuropathological mechanisms. Evening-to-morning variations in waking EEG revealed the gradual disappearance in MCI and AD of overnight changes in delta activity, indicating a progressive decay of sleep restorative functions on diurnal activity that correlates with the impairment of sleep high-frequency activity in AD. Our findings support a linkage between wake and sleep alterations, and the importance of sleep-related processes in Alzheimer's disease progression.

In Search of Sleep Biomarkers of Alzheimer's Disease: K-Complexes Do Not Discriminate between Patients with Mild Cognitive Impairment and Healthy Controls

The K-complex (KC) is one of the hallmarks of Non-Rapid Eye Movement (NREM) sleep. Recent observations point to a drastic decrease of spontaneous KCs in Alzheimer's disease (AD). However, no study has investigated when, in the development of AD, this phenomenon starts. The assessment of KC density in mild cognitive impairment (MCI), a clinical condition considered a possible transitional stage between normal cognitive function and probable AD, is still lacking. The aim of the present study was to compare KC density in AD/MCI patients and healthy controls (HCs), also assessing the relationship between KC density and cognitive decline. Twenty amnesic MCI patients underwent a polysomnographic recording of a nocturnal sleep. Their data were compared to those of previously recorded 20 HCs and 20 AD patients. KCs during stage 2 NREM sleep were visually identified and KC densities of the three groups were compared. AD patients showed a significant KC density decrease compared with MCI patients and HCs, while no differences were observed between MCI patients and HCs. KC density was positively correlated with Mini-Mental State Examination (MMSE) scores. Our results point to the existence of an alteration of KC density only in a full-blown phase of AD, which was not observable in the early stage of the pathology (MCI), but linked with cognitive deterioration.

Parietal Fast Sleep Spindle Density Decrease in Alzheimer's Disease and Amnesic Mild Cognitive Impairment

Several studies have identified two types of sleep spindles: fast (13-15 Hz) centroparietal and slow (11-13 Hz) frontal spindles. Alterations in spindle activity have been observed in Alzheimer's disease (AD) and Mild Cognitive Impairment (MCI). Only few studies have separately assessed fast and slow spindles in these patients showing a reduction of fast spindle count, but the possible local specificity of this phenomenon and its relation to cognitive decline severity are not clear. Moreover, fast and slow spindle density have never been assessed in AD/MCI. We have assessed fast and slow spindles in 15 AD patients, 15 amnesic MCI patients, and 15 healthy elderly controls (HC). Participants underwent baseline polysomnographic recording (19 cortical derivations). Spindles during nonrapid eye movements sleep were automatically detected, and spindle densities of the three groups were compared in the derivations where fast and slow spindles exhibited their maximum expression (parietal and frontal, resp.). AD and MCI patients showed a significant parietal fast spindle density decrease, positively correlated with Minimental State Examination scores. Our results suggest that AD-related changes in spindle density are specific for frequency and location, are related to cognitive decline severity, and may have an early onset in the pathology development.

Neuroplastic effects of combined computerized physical and cognitive training in elderly individuals at risk for dementia: an eLORETA controlled study on resting states

The present study investigates whether a combined cognitive and physical training may induce changes in the cortical activity as measured via electroencephalogram (EEG) and whether this change may index a deceleration of pathological processes of brain aging. Seventy seniors meeting the clinical criteria of mild cognitive impairment (MCI) were equally divided into 5 groups: 3 experimental groups engaged in eight-week cognitive and/or physical training and 2 control groups: active and passive. A 5-minute long resting state EEG was measured before and after the intervention. Cortical EEG sources were modelled by exact low resolution brain electromagnetic tomography (eLORETA). Cognitive function was assessed before and after intervention using a battery of neuropsychological tests including the minimental state examination (MMSE). A significant training effect was identified only after the combined training scheme: a decrease in the post- compared to pre-training activity of precuneus/posterior cingulate cortex in delta, theta, and beta bands. This effect was correlated to improvements in cognitive capacity as evaluated by MMSE scores. Our results indicate that combined physical and cognitive training shows indices of a positive neuroplastic effect in MCI patients and that EEG may serve as a potential index of gains versus cognitive declines and neurodegeneration. This trial is registered with ClinicalTrials.gov Identifier NCT02313935.

Occipital sources of resting-state alpha rhythms are related to local gray matter density in subjects with amnesic mild cognitive impairment and Alzheimer's disease

Occipital sources of resting-state electroencephalographic (EEG) alpha rhythms are abnormal, at the group level, in patients with amnesic mild cognitive impairment (MCI) and Alzheimer's disease (AD). Here, we evaluated the hypothesis that amplitude of these occipital sources is related to neurodegeneration in occipital lobe as measured by magnetic resonance imaging. Resting-state eyes-closed EEG rhythms were recorded in 45 healthy elderly (Nold), 100 MCI, and 90 AD subjects. Neurodegeneration of occipital lobe was indexed by weighted averages of gray matter density, estimated from structural MRIs. EEG rhythms of interest were alpha 1 (8-10.5 Hz) and alpha 2 (10.5-13 Hz). EEG cortical sources were estimated by low-resolution brain electromagnetic tomography. Results showed a positive correlation between occipital gray matter density and amplitude of occipital alpha 1 sources in Nold, MCI, and AD subjects as a whole group (r = 0.3, p = 0.000004, N = 235). Furthermore, there was a positive correlation between the amplitude of occipital alpha 1 sources and cognitive status as revealed by Mini Mental State Examination score across all subjects (r = 0.38, p = 0.000001, N = 235). Finally, amplitude of occipital alpha 1 sources allowed a moderate classification of individual Nold and AD subjects (sensitivity: 87.8%; specificity: 66.7%; area under the receiver operating characteristic curve: 0.81). These results suggest that the amplitude of occipital sources of resting-state alpha rhythms is related to AD neurodegeneration in occipital lobe along pathologic aging.

Stability of clinical condition in mild cognitive impairment is related to cortical sources of alpha rhythms: an electroencephalographic study

Previous evidence has shown that resting eyes-closed cortical alpha rhythms are higher in amplitude in mild cognitive impairment (MCI) than Alzheimer's disease (AD) subjects (Babiloni et al. [2006a]: Human Brain Mapp 27:162-172; [2006b]: Clin Neurophysiol 117:252-268; [2006c]: Neuroimage 29:948-964; [2006d]: Ann Neurol 59:323-334; [2006e]: Clin Neurophysiol 117:1113-1129; [2006f]: Neuroimage 31:1650-1665). This study tested the hypothesis that, in amnesic MCI subjects, high amplitude of baseline cortical alpha rhythms is related to long-term stability of global cognition on clinical follow-up. Resting electroencephalographic (EEG) data were recorded in 100 amnesic MCI subjects during eyes-closed condition. EEG rhythms of interest were delta (2-4 Hz), theta (4-8 Hz), alpha1 (8-10.5 Hz), alpha2 (10.5-13 Hz), beta1 (13-20 Hz), and beta2 (20-30 Hz). Cortical EEG sources were estimated by low-resolution brain electromagnetic tomography (LORETA). Global cognition was indexed by mini mental state evaluation (MMSE) score at the time of EEG recordings (baseline) and about after 1 year. Based on the MMSE percentage difference between baseline and 1-year follow-up (MMSEvar), the MCI subjects were retrospectively divided into three arbitrary groups: DECREASED (MMSEvar ≤ -4%; N = 43), STABLE (MMSEvar ≈ 0; N = 27), and INCREASED (MMSEvar ≥ +4%; N = 30). Subjects' age, education, individual alpha frequency, gender, and MMSE scores were used as covariates for statistical analysis. Baseline posterior cortical sources of alpha 1 rhythms were higher in amplitude in the STABLE than in the DECREASED and INCREASED groups. These results suggest that preserved resting cortical neural synchronization at alpha frequency is related to a long-term (1 year) stable cognitive function in MCI subjects. Future studies should use serial MMSE measurements to confirm and refine the present results.

Screening for mild cognitive impairment in elderly ambulatory patients with cognitive complaints

BACKGROUND AND AIMS

Identification of patients with Mild Cognitive Impairment (MCI) is strongly recommended because of their increased risk of dementia. Two brief global cognitive instruments, the Mini Mental State Examination (MMSE) and the Clock Drawing Test (CDT), were examined as useful screening methods for MCI.

METHODS

The sensitivity and specificity of MMSE and CDT, scored using the Sunderland and Wolf-Klein methods, were evaluated in 113 elderly individuals with three different MCI subtypes: amnestic, multiple domain impairments, and single non-memory domain. Diagnoses were made on the basis of extensive clinical and neuropsychometric assessment.

RESULTS

Used alone, MMSE and CDT at standard cut-offs were highly specific (about 0.80) but rather insensitive (less than 0.50) to all MCI subtypes. By contrast, when used in combination, an abnormal result on either MMSE or CDT scored by the Sunderland method had a specificity of 0.69 [0.57-0.81] and a sensitivity of 0.75 [0.64-0.87] for multiple domain impairments MCI. Results were similar for MMSE in combination with CDT scored by the Wolf-Klein method (specificity 0.71 [0.59-0.83]; sensitivity 0.68 [0.56-0.80]).

CONCLUSIONS

MMSE and CDT alone are not valid screening methods for MCI detection. In combination, they reach fair sensitivity and specificity for the multiple domain impairment MCI subtype. However, some theoretical concerns relating to this subtype, together with the uncertainty that still lingers about its prognostic value, caution against routine use of MMSE and CDT as MCI screening instruments.

Association of cognitive status with functional limitation and disability in older adults

BACKGROUND AND AIMS

Although cognitive status is known to be associated with physical function in older people, the role it plays in the disability process is not well established. This study aimed at determining whether cognitive ability predicts functional limitations, as well as disability, and whether it is associated with the rate of change in physical functions.

METHODS

A community-based longitudinal study was conducted, involving 977 older persons aged 65 and older living in an urban community. Physical functions were assessed by tests scoring functional limitations (upper and lower body) and disability (activities of daily living). Cognitive function was evaluated using the Mini-Mental State Examination. Linear regression analyses with generalized estimating equations modeled the two physical function scores separately, as functions of cognitive status and time, in a one-year follow-up, controlling for sociodemographic and health-related characteristics.

RESULTS

Cognitive status independently predicted functional limitations as well as disability in older people. In addition, the strength of the association of cognitive status with physical functions increased over time, as revealed by the significant interaction between cognitive ability and time. Cognitive status influenced the rate of change in disability scores, more among women and in those aged 75 or older. The relationship was unaffected by baseline physical functional status, but was significant only among those with no cognitive impairment at baseline.

CONCLUSIONS

Cognitive status appears to be a useful indicator of the disablement process in older people. It may play an important role in the development of disability, implying that strategies for early intervention to prevent the progression of disability may need to take cognitive functions into account. The increasing strength of the relationship between cognitive and physical functions over time further attests to its value in monitoring functional change.

Vers une prévention de la démence ?

Many studies have shown that high blood pressure and, to a lesser extent, other vascular risk factors could be the target of interventions aiming to reduce the incidence of dementia. Two large controlled trials have demonstrated that blood pressure lowering drugs have a significant effect on the risk of dementia including Alzheimer's disease. On another hand, large epidemiological studies have shown associations between different vascular factors and dementia. Overall, these data suggest that interventions aiming to reduce the level of vascular risk factors might prevent dementia. The expected benefit of these interventions could be estimated from data provided by epidemiological studies, but large population-based controlled studies are needed to demonstrate the efficacy of preventive interventions.

Memory and metamemory performance in Alzheimer's disease and healthy elderly: the Contextual Memory Test (CMT)

The purpose of the present study was to examine the ability of the Contextual Memory Test (CMT) to differentiate between elderly people suffering from Alzheimer's disease (AD) in comparison to healthy elderly people. Specifically, the objectives were to compare for differences between and within the groups on components of memory, including immediate and delayed recall as well as recognition. In addition, parameters of metamemory skills, such as general awareness, self-prediction of memory capacity, self-estimation, strategy use and use of contextual information, as well as the correlation between self-awareness and actual performance in both groups, were investigated. The sample consisted of 60 elderly participants, including 30 people diagnosed with AD who were assigned to the research group and 30 people matched for age, gender and educational level who were assigned to the control group. The results provide support for the hypothesis positing differences in memory performance between healthy elderly participants and those suffering from AD, particularly in immediate and delayed recall as well as in recognition. Moreover, findings indicate an improvement in memory performance under the cued condition (contextual), whereas improvement in the AD group proved to be significant only for immediate recall. The findings point to a distinct overestimation of memory ability predicted by both the AD and control groups. Following the memory task, however, the participants accurately estimated the number of items they remembered. In addition, significant correlations between the use of contextual and association strategies and the number of items remembered by both groups were obtained, in immediate as well as in delayed recall. Therefore, these findings support the CMT as a valuable memory and metamemory assessment tool for use with the AD population.