Natural history of mild cognitive impairment in older persons

Exposure to secondhand smoke and cognitive impairment in non-smokers: national cross sectional study with cotinine measurement

OBJECTIVE

To examine the association between a biomarker of exposure to secondhand smoke (salivary cotinine concentration) and cognitive impairment.

DESIGN

Cross sectional analysis of a national population based study.

SETTING

Stratified random sample of households throughout England.

PARTICIPANTS

4809 non-smoking adults aged 50 years or more from the 1998, 1999, and 2001 waves of the Health Survey for England who also participated in the 2002 wave of the English Longitudinal Study of Ageing and provided saliva samples for cotinine assay and a detailed smoking history.

MAIN OUTCOME MEASURE

Cognitive impairment as defined by the lowest 10% of scores on a battery of neuropsychological tests.

RESULTS

Participants who did not smoke, use nicotine products, or have salivary cotinine concentrations of 14.1 ng/ml or more were divided into four equal size groups on the basis of cotinine concentrations. Compared with the lowest fourth of cotinine concentration (0.0-0.1 ng/ml) the odds ratios (95% confidence intervals) for cognitive impairment in the second (0.2-0.3 ng/ml), third (0.4-0.7 ng/ml), and highest fourths (0.8-13.5 ng/ml) were 1.08 (0.78 to 1.48), 1.13 (0.81 to 1.56), and 1.44 (1.07 to 1.94; P for trend 0.02), after adjustment for a wide range of established risk factors for cognitive impairment. A similar pattern of associations was observed for never smokers and former smokers.

CONCLUSIONS

Exposure to secondhand smoke may be associated with increased odds of cognitive impairment. Prospective nationally representative studies relating biomarkers of exposure to cognitive decline and risk of dementia are needed.

Do CSF total tau, phosphorylated tau, and beta-amyloid 42 help to predict progression of mild cognitive impairment to Alzheimer's disease? A systematic review and meta-analysis of the literature

The search for biomarkers as a diagnostic aid to the identification of patients in pre-dementia stages is a fast growing research area. In view of the low specificity attained with the clinically based diagnostic criteria, including those for mild cognitive impairment (MCI), biomarker information will add precision to the incipient dementia diagnostic work-up, particularly Alzheimer's disease (AD). We present a systematic review of the literature and meta-analysis of the most relevant publications about the role of CSF biomarkers in the identification of patients with probable Alzheimer's disease at pre-dementia stages. A total of 16 studies were included in the systematic review, five of which were suitable for meta-analysis. We compared the standard mean differences (SMD) of beta-amyloid 42 (Abeta42), total tau (T-tau) and phosphorylated tau (P-tau) for 130, 169 and 123 patients with MCI who converted to AD (MCI-AD) and 142, 157 and 130 controls, respectively. We conclude that when a clinical diagnosis of MCI is made at baseline assessment, low CSF levels of Abeta42 (SMD: -1.57, CI 95% [-2.30 to -0.84], P < 0.001), along with high T-tau (SMD: 1.52, CI 95% [1.25 to 1.79], P < 0.001), and high P-tau (SMD: 1.75, CI 95% [0.99 to 2.51], P < 0.001), help to predict the conversion to Alzheimer's disease as compared to controls subjects.

Lay Appraisal of Cognitive Impairment Symptoms and Related Prevention Beliefs in a Community-Dwelling Sample of Midlife and Older Adults

This study explores how age and health-related quality of life (HRQoL) may be related to the identification and appraisal of cognitive impairment symptoms as well as associated prevention beliefs. Participants were 140 community-dwelling adults ranging in age from 49 to 90 years who completed a survey containing a vignette about an adult with cognitive impairment symptoms and questions about the illness symptoms, prevention beliefs, and HRQoL. Identification of symptoms as Alzheimer's disease or dementia was reported by 83% of respondents. Correlational analyses suggested age and education to be associated with perceived significance of symptoms as well as the recommendation to seek medical care. Multiple regression modeling indicated interactive effects that suggest advancing age and poor HRQoL may be associated with greater delay in seeking care for cognitive impairment symptoms and unrealistic optimism regarding prevention outcomes. Educational interventions to bolster the individuals' and caregivers' knowledge of Alzheimer's disease are discussed.

Serum zinc in the progression of Alzheimer's disease

Previous studies show significantly decreased levels of zinc transporter 1 (ZnT-1) in the brain of subjects with mild cognitive impairment (MCI) but significantly increased ZnT-1 in late stage AD (LAD). However, the reason for the apparent dichotomy is unclear. Based on in vivo studies that show animals provided a zinc (Zn) deficient diet demonstrate decreased brain ZnT-1, we used inductively coupled plasma-mass spectrometry (ICP-MS) to quantify serum Zn levels from 18 living mild to moderate AD patients (9 men, 9 women), 19 MCI patients (9 men, 10 women) and 16 age-matched normal control (NC) subjects (9 men, 7 women). Zinc levels for all subjects were not significantly different among any of the three subject groups. However, there was a statistically significant decrease of serum Zn (11.7 +/- 0.5 microM) in men with MCI compared to women with MCI (13.7 +/- 0.6 microM) and NC men (13.9 +/- 0.6 microM). Serum Zn levels in probable AD patients were comparable to those in NC subjects. Overall, these data suggest a significant decrease of serum Zn in men with MCI, may explain the loss of ZnT-1 observed in previous studies and suggest there may be more pronounced sex differences in MCI than were previously recognized.

Target identification for CNS diseases by transcriptional profiling

Gene expression changes in neuropsychiatric and neurodegenerative disorders, and gene responses to therapeutic drugs, provide new ways to identify central nervous system (CNS) targets for drug discovery. This review summarizes gene and pathway targets replicated in expression profiling of human postmortem brain, animal models, and cell culture studies. Analysis of isolated human neurons implicates targets for Alzheimer's disease and the cognitive decline associated with normal aging and mild cognitive impairment. In addition to tau, amyloid-beta precursor protein, and amyloid-beta peptides (Abeta), these targets include all three high-affinity neurotrophin receptors and the fibroblast growth factor (FGF) system, synapse markers, glutamate receptors (GluRs) and transporters, and dopamine (DA) receptors, particularly the D2 subtype. Gene-based candidates for Parkinson's disease (PD) include the ubiquitin-proteosome system, scavengers of reactive oxygen species, brain-derived neurotrophic factor (BDNF), its receptor, TrkB, and downstream target early growth response 1, Nurr-1, and signaling through protein kinase C and RAS pathways. Increasing variability and decreases in brain mRNA production from middle age to old age suggest that cognitive impairments during normal aging may be addressed by drugs that restore antioxidant, DNA repair, and synaptic functions including those of DA to levels of younger adults. Studies in schizophrenia identify robust decreases in genes for GABA function, including glutamic acid decarboxylase, HINT1, glutamate transport and GluRs, BDNF and TrkB, numerous 14-3-3 protein family members, and decreases in genes for CNS synaptic and metabolic functions, particularly glycolysis and ATP generation. Many of these metabolic genes are increased by insulin and muscarinic agonism, both of which are therapeutic in psychosis. Differential genomic signals are relatively sparse in bipolar disorder, but include deficiencies in the expression of 14-3-3 protein members, implicating these chaperone proteins and the neurotransmitter pathways they support as possible drug targets. Brains from persons with major depressive disorder reveal decreased expression for genes in glutamate transport and metabolism, neurotrophic signaling (eg, FGF, BDNF and VGF), and MAP kinase pathways. Increases in these pathways in the brains of animals exposed to electroconvulsive shock and antidepressant treatments identify neurotrophic and angiogenic growth factors and second messenger stimulation as therapeutic approaches for the treatment of depression.

A potential role for alterations of zinc and zinc transport proteins in the progression of Alzheimer's disease

Although multiple studies have suggested a role for alterations of zinc (Zn) and zinc transport (ZnT) proteins in the pathogenesis of Alzheimer's disease, the exact role of this essential trace element in the progression of the disease remains unclear. The following review discusses the normal role of Zn and ZnT proteins in brain and the potential effects of their alteration in the pathogenesis of Alzheimer's disease, particularly in the processing of the amyloid-beta protein precursor and amyloid-beta peptide generation and aggregation.

Global Functional Coupling of Resting EEG Rhythms is Abnormal in Mild Cognitive Impairment and Alzheimer’s Disease

Alzheimer’s disease (AD) is typically associated with an impairment of brain networks and global cognitive function in aging. In this vein, the present study tested the hypothesis that the functional coupling of resting cortical electroencephalographic (EEG) rhythms is progressively abnormal in amnesic mild cognitive impairment (MCI) and AD subjects. Eyes-closed resting EEG data were recorded (10–20 system) in 33 mild AD, 52 amnesic MCI, and 47 normal elderly subjects (Nold). EEG rhythms of interest were delta (2–4 Hz), theta (4–8 Hz), alpha1 (8–10 Hz), alpha2 (10–13 Hz), beta1 (13–20 Hz), beta2 (20–30 Hz), and gamma (30–40 Hz). The global functional coupling of the EEG rhythms was indexed by means of spectral coherence for all combinations of electrode pairs (i.e., total coherence). The main results showed that the total coherence of delta rhythms was higher in the AD than the MCI group. It was also higher in the MCI than the Nold group. Furthermore, the delta total coherence was negatively correlated with global cognition (Mini Mental State Examination score) across the Nold, MCI, and AD subjects. Finally, the alpha1 total coherence was lower in the AD group than in the MCI and Nold groups. These results suggest that in the AD process an impairment of brain networks and global cognition is associated with a frequency-specific modulation of the global functional coupling of resting EEG rhythms.

Mild cognitive impairment: cognitive screening or neuropsychological assessment?

OBJECTIVE: To describe the neuropsychological profile of mild cognitive impairment subtypes (amnestic, non-amnestic and multiple-domain) of a clinical sample. We further address the diagnostic properties of the Mini-Mental State Examination and the Cambridge Cognitive Examination for the identification of the different mild cognitive impairment subtypes in clinical practice. METHOD: Cross-sectional clinical and neuropsychological evaluation of 249 elderly patients attending a memory clinic at a university hospital in Sao Paulo, Brazil. RESULTS: The performance of patients with mild cognitive impairment was heterogeneous across the different subtests of the neuropsychological battery, with a trend towards an overall worse performance for amnestic (particularly multiple domain) mild cognitive impairment as compared to non-amnestic subtypes. Screening tests for dementia (Mini-Mental State Examination and Cambridge Cognitive Examination) adequately discriminated cases of mild Alzheimer's disease from controls, but they were not accurate to discriminate patients with mild cognitive impairment (all subtypes) from control subjects. CONCLUSIONS: The discrimination of mild cognitive impairment subtypes was possible only with the aid of a comprehensive neuropsychological assessment. It is necessary to develop new strategies for mild cognitive impairment screening in clinical practice.

EEG Patterns in Mild Cognitive Impairment (MCI) Patients

An emerging clinical priority for the treatment of Alzheimer's disease (AD) is the implementation of therapies at the earliest stages of disease onset. All AD patients pass through an intermediary stage of the disorder known as Mild Cognitive Impairment (MCI), but not all patients with MCI develop AD. By applying computer based signal processing and pattern recognition techniques to the electroencephalogram (EEG), we were able to classify AD patients versus controls with an accuracy rate of greater than 80%. We were also able to categorize MCI patients into two subgroups: those with EEG Beta power profiles resembling AD patients and those more like controls. We then used this brain-based classification to make predictions regarding those MCI patients most likely to progress to AD versus those who would not. Our classification algorithm correctly predicted the clinical status of 4 out of 6 MCI patients returning for 2 year clinical follow-up. While preliminary in nature, our results suggest that automated pattern recognition techniques applied to the EEG may be a useful clinical tool not only for classification of AD patients versus controls, but also for identifying those MCI patients most likely to progress to AD.

Medical decision-making capacity in mild cognitive impairment: a 3-year longitudinal study

OBJECTIVE

To investigate longitudinal change in the medical decision-making capacity (MDC) of patients with amnestic mild cognitive impairment (MCI) under different consent standards.

METHODS

Eighty-eight healthy older controls and 116 patients with MCI were administered the Capacity to Consent to Treatment Instrument at baseline and at 1 to 3 (mean = 1.7) annual follow-up visits thereafter. Covariate-adjusted random coefficient regressions were used to examine differences in MDC trajectories across MCI and control participants, as well as to investigate the impact of conversion to Alzheimer disease on MCI patients' MDC trajectories.

RESULTS

At baseline, MCI patients performed significantly below controls only on the three clinically relevant standards of appreciation, reasoning, and understanding. Compared with controls, MCI patients experienced significant declines over time on understanding but not on any other consent standard. Conversion affected both the elevation (a decrease in performance) and slope (acceleration in subsequent rate of decline) of MCI patients' MDC trajectories on understanding. A trend emerged for conversion to be associated with a performance decrease on reasoning in the MCI group.

CONCLUSIONS

Medical decision-making capacity (MDC) decline in mild cognitive impairment (MCI) is a relatively slow but detectable process. Over a 3-year period, patients with amnestic MCI show progressive decline in the ability to understand consent information. This decline accelerates after conversion to Alzheimer disease (AD), reflecting increasing vulnerability to decisional impairment. Clinicians and researchers working with MCI patients should give particular attention to the informed consent process when conversion to AD is suspected or confirmed.

The effects of exercise on cognition in older adults with and without cognitive decline: a systematic review

OBJECTIVE

To systematically review the effect of physical exercise on cognition in older adults with and without cognitive decline.

DATA SOURCES

: Randomized controlled trials were identified by literature searches in PubMed, EMBASE, CENTRAL, PsycINFO, and AgeLine.

STUDY SELECTION

Papers were included on the basis of predefined inclusion criteria.

DATA EXTRACTION

Data on study population, exercise intervention, and effectiveness were extracted. Two independent reviewers assessed methodological quality.

DATA SYNTHESIS

Twenty-three studies were included-15 among cognitively healthy subjects and 8 among subjects with cognitive decline. Seven studies were qualified as high-quality studies, 2 in cognitively healthy subjects and 5 in subjects with cognitive decline. In cognitively healthy subjects, significant beneficial intervention effects were observed in 5 studies on information processing, executive function, or memory. Interventions in these studies included aerobic exercise only (n = 2); strength exercise (n = 1); strength and balance exercise (n = 1); or all-round exercise including aerobic, strength, balance and flexibility training (n = 1). In subjects with cognitive decline, 5 studies observed beneficial effects on general cognition, executive functions, and memory. Interventions included aerobic (n = 3) or strength exercise combined with flexibility or balance exercise (n = 2).

CONCLUSIONS

Beneficial effects of various exercise programs on aspects of cognition have been observed in studies among subjects with and without cognitive decline. The majority of the studies, however, did not find any effect. The small number of included studies; lack of high-quality studies; and the large variability in study populations, exercise protocols, and outcome measures complicate interpretation of the results. More high-quality trials are needed to assess the effects of different types of exercise on cognitive function in older adults with and without cognitive decline.

Alzheimer's disease and mild cognitive impairment deteriorate fine movement control

Sensory-motor dysfunctions are often associated with Alzheimer's disease (AD) or mild cognitive impairment (MCI). This study suggests that deterioration in fine motor control and coordination characterizes sensory-motor deficiencies of AD and MCI. Nine patients with a clinical diagnosis of probable AD, 9 amnestic MCI subjects and 10 cognitively normal controls performed four types of handwriting movement on a digitizer. Movement time and smoothness were analyzed between the groups and across the movement patterns. Kinematic profiles were also compared among the groups. AD and MCI patients demonstrated slower, less smooth, less coordinated, and less consistent handwriting movements than their healthy counterparts. The theoretical relevance and practical implications of fine motor tasks, such as these movements involved in handwriting, are discussed relative to the deteriorated sensory-motor system of AD and MCI patients.

Periventricular white matter hyperintensities increase the likelihood of progression from amnestic mild cognitive impairment to dementia

BACKGROUND

White matter hyperintensities (WMH) have an effect on cognition and are increased in severity among individuals with amnestic mild cognitive impairment (aMCI). The influence of WMH on progression of aMCI to Alzheimer's disease (AD) is less clear.

METHODS

Data were drawn from a three-year prospective, double blind, placebo controlled clinical trial that examined the effect of donepezil or vitamin E on progression from aMCI to AD. WMH from multiple brain regions were scored on MR images obtained at entry into the trial from a subset of 152 study participants using a standardized visual rating scale. Cox proportional hazards models adjusting for age, education and treatment arm were used to investigate the role of WMH on time to progression.

RESULTS

55 of the 152 (36.2 %) aMCI subjects progressed to AD. Only periventricular hyperintensities (PVH) were related to an increased risk of AD within three years (HR = 1.59, 95 % CI = 1.24 - 2.05, p-value < 0.001). Correcting for medial temporal lobe atrophy or the presence of lacunes did not change statistical significance.

CONCLUSION

PVH are associated with an increased risk of progression from aMCI to AD. This suggests that PVH, an MRI finding thought to represent cerebrovascular damage, contributes to AD onset in vulnerable individuals independent of Alzheimer pathology.

Language performance in Alzheimer's disease and mild cognitive impairment: a comparative review

Mild cognitive impairment (MCI) manifests as memory impairment in the absence of dementia and progresses to Alzheimer's disease (AD) at a rate of around 15% per annum, versus 1-2% in the general population. It thus constitutes a primary target for investigation of early markers of AD. Language deficits occur early in AD, and performance on verbal tasks is an important diagnostic criterion for both AD and MCI. We review language performance in MCI, compare these findings to those seen in AD, and identify the primary issues in understanding language performance in MCI and selecting tasks with diagnostic and prognostic value.

Rate of entorhinal and hippocampal atrophy in incipient and mild AD: relation to memory function

In the present study, as part of a more extensive longitudinal investigation of the in vivo anatomical markers of early and incipient AD in our laboratory, three groups of elderly participants were followed with yearly clinical evaluations and high resolution MRI scans over a 6-year period (baseline and 5 years of follow-up). At baseline, participants consisted of: (1) 35 old subjects with no cognitive impairment (controls); (2) 33 participants with amnestic mild cognitive impairment (MCI); and (3) 14 patients with very mild AD. 11 participants with amnestic MCI received a diagnosis of AD over the follow-up period and 9 controls declined in cognitive function. T1 weighted MRI scans were acquired using a 3D SPGR pulse sequence. At baseline, both the amnestic MCI and mild AD groups differed from the controls in hippocampal and entorhinal cortex volume, but not from each other. Longitudinal analyses showed that the rate of atrophy of the entorhinal cortex and hippocampus for the stable controls differed significantly from MCI participants who converted to AD and the AD groups. Furthermore, longitudinal decreases in hippocampal and entorhinal volume were related to longitudinal decline in declarative memory performance. These findings suggest that the rate of atrophy of mesial temporal lobe structures can differentiate healthy from pathological aging.

Respiratory muscle strength predicts decline in mobility in older persons

OBJECTIVES

To test the hypothesis that respiratory muscle strength is associated with the rate of change in mobility even after controlling for leg strength and physical activity.

METHODS

Prospective study of 890 ambulatory older persons without dementia who underwent annual clinical evaluations to examine change in the rate of mobility over time.

RESULTS

In a linear mixed-effect model adjusted for age, sex, and education, mobility declined about 0.12 unit/year, and higher levels of respiratory muscle strength were associated with a slower rate of mobility decline (estimate 0.043, SE 0.012, p < 0.001). Respiratory muscle strength remained associated with the rate of change in mobility even after controlling for lower extremity strength (estimate 0.036, SE 0.012, p = 0.004). In a model that included terms for respiratory muscle strength, lower extremity strength and physical activity together, all three were independent predictors of mobility decline in older persons. These associations remained significant even after controlling for body composition, global cognition, the development of dementia, parkinsonian signs, possible pulmonary disease, smoking, joint pain and chronic diseases.

CONCLUSION

Respiratory muscle strength is associated with mobility decline in older persons independent of lower extremity strength and physical activity. Clinical interventions to improve respiratory muscle strength may decrease the burden of mobility impairment in the elderly.

Consortium to Establish a Registry for Alzheimer's Disease (CERAD): the first twenty years

The Consortium to Establish a Registry for Alzheimer's Disease (CERAD) was funded by the National Institute on Aging in 1986 to develop standardized, validated measures for the assessment of Alzheimer's disease (AD). The present report describes the measures that CERAD developed during its first decade and their continued use in their original and translated forms. These measures include clinical, neuropsychological, neuropathologic, and behavioral assessments of AD and also assessment of family history and parkinsonism in AD. An approach to evaluating neuroimages did not meet the standards desired. Further evaluations that could not be completed because of lack of funding (but where some materials are available) include evaluation of very severe AD and of service use and need by patient and caregiver. The information that was developed in the U.S. and abroad permits standardized assessment of AD in clinical practice, facilitates epidemiologic studies, and provides information valuable for individual and public health planning. CERAD materials and data remain available for those wishing to use them.

Functional abnormalities of the visual processing system in subjects with mild cognitive impairment: an fMRI study

Subjects with mild cognitive impairment (MCI) have a higher risk of developing Alzheimer's disease compared with healthy controls (HC). Sensory impairment can contribute to the severity of cognitive impairment. We measured the activation changes in the visual system between MCI and HC subjects. There were 16 MCI subjects with either amnestic MCI or multiple-domain+amnestic MCI and an HC group of 19 subjects. There were two tasks: (a) a face matching and (b) a location matching task. Brain activation was measured using functional magnetic resonance imaging. There were no differences in task performance. The HC group selectively activated the ventral and dorsal pathways during the face and location matching tasks, respectively, while the MCI group did not. The MCI group had greater activation than the HC group in the left frontal lobe during the location matching task. There were no areas of increased activation in the HC group compared with the MCI group. The MCI group, as a compensatory mechanism, activated both visual pathways and increased activation in the left frontal lobe during the location matching task compared with the healthy controls. To our knowledge, this is the first study that has examined visual processing in MCI.

EEG Patterns in Mild Cognitive Impairment (MCI) Patients

An emerging clinical priority for the treatment of Alzheimer’s disease (AD) is the implementation of therapies at the earliest stages of disease onset. All AD patients pass through an intermediary stage of the disorder known as Mild Cognitive Impairment (MCI), but not all patients with MCI develop AD. By applying computer based signal processing and pattern recognition techniques to the electroencephalogram (EEG), we were able to classify AD patients versus controls with an accuracy rate of greater than 80%. We were also able to categorize MCI patients into two subgroups: those with EEG Beta power profiles resembling AD patients and those more like controls. We then used this brain-based classification to make predictions regarding those MCI patients most likely to progress to AD versus those who would not. Our classification algorithm correctly predicted the clinical status of 4 out of 6 MCI patients returning for 2 year clinical follow-up. While preliminary in nature, our results suggest that automated pattern recognition techniques applied to the EEG may be a useful clinical tool not only for classification of AD patients versus controls, but also for identifying those MCI patients most likely to progress to AD.

Does cognition predict mortality in midlife? Results from the Whitehall II cohort study

The authors examined the association of 'g' (general intelligence) factor and five specific cognitive measures assessed in 1997-1999 with mortality till 2006 (mean follow-up of 8 years) in the middle-aged Whitehall II cohort study. In age- and sex-adjusted analysis, a decrease in 1 S.D. in memory (hazard ratio (HR), 1.19; 95% confidence interval (CI): 1.02, 1.39) and in Alice Heim 4-I (AH4-I) (HR, 1.16; 95% CI: 1.01, 1.35) was found to be associated with higher mortality. The association with 'g' factor, phonemic and semantic fluency did not reach significance at p<0.05. No association was found with vocabulary. Out of education, health behaviours and health measures, it was health behaviours that explained the greater part of the association between cognition and mortality, ranging from 21% for memory to 70% for semantic fluency. All the covariates taken together explained only 26% of the association with memory and between 33 and 90% for the other cognitive measures. This study suggests that 'g' type composite measure of cognition might not be enough to understand the associations between cognition and health.

Diagnosis and treatment of dementia: 3. Mild cognitive impairment and cognitive impairment without dementia

BACKGROUND

Mild cognitive impairment and cognitive impairment, no dementia, are emerging terms that encompass the clinical state between normal cognition and dementia in elderly people. Controversy surrounds their characterization, definition and application in clinical practice. In this article, we provide physicians with practical guidance on the definition, diagnosis and treatment of mild cognitive impairment and cognitive impairment, no dementia, based on recommendations from the Third Canadian Consensus Conference on the Diagnosis and Treatment of Dementia, held in March 2006.

METHODS

We developed evidence-based guidelines using systematic literature searches, with specific criteria for study selection and quality assessment, and a clear and transparent decision-making process. We selected studies published from January 1996 to December 2005 that had mild cognitive impairment or cognitive impairment, no dementia, as the outcome. Subsequent to the conference, we searched for additional articles published between January 2006 and January 2008. We graded the strength of evidence using the criteria of the Canadian Task Force on Preventive Health Care.

RESULTS

We identified 2483 articles, of which 314 were considered to be relevant and of good or fair quality. From a synthesis of the evidence in these studies, we made 16 recommendations. In brief, family physicians should be aware that most types of dementia are preceded by a recognizable phase of mild cognitive decline. They should be familiar with the concepts of mild cognitive impairment and of cognitive impairment, no dementia. Patients with these conditions should be closely monitored because of their increased risk for dementia. Leisure activities, cognitive stimulation and physical activity could be promoted as part of a healthy lifestyle in elderly people and those with mild cognitive impairment. Vascular risk factors should be treated optimally. No other specific therapies can yet be recommended.

INTERPRETATION

Physicians will increasingly see elderly patients with mild memory loss, and learning an approach to diagnosing states such as mild cognitive impairment is now warranted. Close monitoring for progression to dementia, promotion of a healthy lifestyle and treatment of vascular risk factors are recommended for the management of patients with mild cognitive impairment.

Frequency and course of mild cognitive impairment in a multiethnic community

OBJECTIVE

To examine incidence rates and antecedents of mild cognitive impairment (MCI) and Alzheimer's disease (AD) among diverse elders without dementia at the initial visit, and to examine the characteristics of elders with MCI who reverted to normal on follow-up examination.

METHODS

A total of 2,364 Caribbean Hispanic, black, or non-Hispanic white subjects, aged 65 or older, who were free of dementia at initial evaluation were followed up every 18 to 24 months. Incidence rate of MCI and AD was determined by examination of neurological, medical, psychiatric, and neuropsychological function.

RESULTS

Over 10,517 person-years, 21% of normal elderly subjects progressed to MCI (annual incidence rate, 5.1%; 95% confidence interval, 4.6-5.6%). Of those with MCI initially, 21.8% were subsequently diagnosed with AD (annual incidence rate, 5.4%; 95% confidence interval, 4.7-6.3%), 47% remained unchanged, and 31% reverted to normal. Those with MCI were 2.8 times more likely to experience development of AD than normal elderly subjects. MCI with impairment in memory and at least one other cognitive domain was associated with greatest risk for progression to AD and was also least likely to revert to normal at follow-up. Consistent diagnosis of MCI or incident probable or possible AD was 60% sensitive and 94% specific for the pathological diagnosis of AD.

INTERPRETATION

Impaired memory and language were useful predictors of transition to AD. Reversion to normal from MCI was frequent, but those with impairment in more than one cognitive domain were more likely to progress or remain impaired than those with single-domain impairment. Clinical diagnosis of MCI does not always predict AD neuropathology.

Prevalence of Alzheimer's dementia and its risk factors in community-dwelling elderly koreans

OBJECTIVE

We estimated the prevalence of Alzheimer's dementia (AD) and mild cognitive impairment (MCI) and their risk factors in an urban community setting, focusing especially on metabolic syndrome.

METHODS

A two-phase investigation based on a door-to-door survey was performed. In Phase I, we administered the Korean version of the Mini-Mental State Examination (MMSE-KC) of the Consortium to Establish a Registry for Alzheimer's disease (CERAD-K). Assessment Packet and the Korean version of the Geriatric Depression Scales (GDS-K) to all 706 participants aged 65 years or older. In Phase II of the study, 175 persons underwent physical and neurological examinations according to the protocol of the CERAD-K clinical assessment battery [CERAD-K (C)] and the neuropsychological assessment battery [CERAD-K (N)]. We also examined the association between cognitive decline and metabolic syndrome. AD and MCI were defined using the DSM-IV-TR criteria and the Clinical Dementia Rating (CDR) scales.

RESULTS

The mean age (+/-SD) of the subjects was 74.3+/-16.7 years and the ratio of males to females was 53.2 to 46.8. The prevalence of Alzheimer's dementia was 9.0%, while that of MCI was 32.9%. Old age and lower educational level had significant associations with cognitive decline in the elderly, but gender, years of alcohol intake or smoking, and metabolic syndrome were not associated with AD or MCI.

CONCLUSION

In this study, metabolic syndrome was not associated with Alzheimer's AD or MCI. Information regarding an association between Alzheimer's dementia and metabolic syndrome in this study will be helpful in formulating future public health policy and prevention strategies in Korea.

A 2-year follow-up of 233 very mild (CDR 0.5) Alzheimer's disease patients (REAL.FR cohort)

OBJECTIVES

Making an early diagnosis of Alzheimer's Disease (AD) is becoming increasingly important. The Clinical Dementia Rating scale (CDR), a semi-structured interview with patient and caregiver, is a global rating scale designed for use in staging dementia. The primary objective of our study was to examine the evolution of AD in individuals with very mild AD (CDR 0.5) across a 2-year follow up.

METHODS

A cohort of AD patients (n=682) living in the community were followed during 2 years in 16 centres of the French AD network. Each subject underwent extensive medical examination including the MMSE and CDR every 6 months.

RESULTS

Two hundred and thirty-three AD patients were rated CDR 0.5 at baseline (mean MMSE score: 23.15+/-2.57). They were younger and reported an average duration of symptoms of approximately 0.8 years less than patients with CDR >or= 1.During the 2-year follow-up, none of the AD CDR 0.5 subjects improved; 65% of them showed an increase in the CDR score. The rate of cognitive decline was similar between the AD CDR 0.5 and CDR >or= 1 groups. The ADL decline was more significant in patients with CDR >or= 1 at inclusion.

CONCLUSIONS

It is certainly possible to identify AD at a very early stage focusing on intra individual change in cognitive and functional impairment. Criteria with a high sensitivity and specificity for detecting AD at an early stage will help to further develop effective pharmacological and behavioural interventions for delaying the onset and progression of the disease.

Decline in verbal memory in non-demented older adults

Decline in memory function was detected in 30% of healthy community-dwelling elderly over 6 years using a task assessing delayed word list recall. Individuals with memory decline over time also demonstrated relative deficits on additional tasks of memory and learning, a task of working memory and executive function, and on a verbal (category) fluency task at their most recent assessment. These relative deficits in the performance of individuals with memory decline cannot be explained by age-related changes, education, intelligence, mood, health-related factors, or the individuals' APOE epsilon 4 status. Decline in memory performance did not result in greater complaints of cognitive difficulties when compared with normal elderly, nor did it limit overall participation in life activities. Although the significance of memory decline in the current study was not determined quantitatively, memory decline is consistent with the early deterioration characteristic of mild cognitive impairment and preclinical Alzheimer's disease and confirms the need to monitor individuals with objective memory decline, even when these individuals fall within normal limits for a given neuropsychological task.

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

OBJECTIVES

The proposals for classifying the transitional range between normal, ageing-associated cognitive dysfunctions and those suggestive of evolution towards dementia do not clarify whether the profiles are risk indicators of later cognitive impairment or represent preclinical phases of dementia.

METHODS

Retrospective study of the baseline neuropsychological performance of ten subjects with subjective complaints of memory loss which evolved to dementia within 2 years and who meet clinical and neurological diagnosis for Probable Alzheimer's Disease (Progression group). They were compared with 34 normal subjects (Normative group), 33 patients with subjective complaints of memory who in 2 year did not evolve towards dementia and presented a stable profile (Stable group), and 47 Alzheimer's patients (Alzheimer group). A broad neuropsychological battery was administered to assess a range of cognitive functions.

RESULTS

The Progression group presented a globally poor baseline neuropsychological performance, except in Working Memory, with clear deficits in Episodic Memory and Visual Memory. In the logistic regression analysis, Delayed Verbal Memory was significant as prognostic value for 80 . 5% of cases.

CONCLUSION

Deficit on Episodic and Visual Memory at least 1.5 SD below T = 50 are preclinical manifestations of dementia in subjects with complain of memory loss. The use of broad neuropsychological batteries and the quantitative assessment of deficits is essential to identify and predict the risk of dementia.

Neuropsychological correlates of self-reported depression and self-reported cognition among patients with mild cognitive impairment

Patients with mild cognitive impairment (MCI) frequently experience significant depressive symptomatology and report cognitive disturbances. To date, no studies have examined the relationship between MCI patients' neuropsychologic functioning, self-reported depressive symptoms, and self-reported cognitive difficulties. In this study, 82 MCI patients completed a comprehensive neuropsychological evaluation that included the Beck Depression Inventory (BDI). A subset of 41 patients and informants also completed a measure of cognitive difficulties. Poorer memory functioning was associated with fewer self-reported depressive symptoms and fewer cognitive complaints.

Oxidative damage in mild cognitive impairment and early Alzheimer's disease

Increasing evidence supports a role for oxidative damage in the pathogenesis of Alzheimer's disease (AD). Multiple studies show significantly increased levels of lipid peroxidation and protein, DNA, and RNA oxidation in vulnerable regions of the brain of patients with late-stage AD (LAD). More recent studies of patients with amnestic mild cognitive impairment (MCI), the earliest clinical manifestation of AD, show similar patterns of oxidative damage. These observations suggest that oxidative damage to critical biomolecules occurs early in the pathogenesis of AD and precedes pronounced neuropathologic alterations. Because oxidative damage begins early in the progress of the disease, it represents a potential therapeutic target for slowing the onset and progression of AD.

Neuronal LR11/sorLA expression is reduced in mild cognitive impairment

OBJECTIVE

LR11 (aka sorLA) is a multifunctional neuronal receptor that binds apolipoprotein E and interacts with amyloid precursor protein to regulate amyloidogenesis. Reduced expression of LR11, as occurs in the brains of individuals with Alzheimer's disease (AD), increases amyloidogenesis, and variants in the gene that encodes LR11, SORL1, have recently been linked to risk for late-onset AD. In this study, we sought to determine whether reduced expression of LR11 occurs early in the disease process and whether protein levels in cortical neurons are associated with clinical and pathological changes in mild cognitive impairment (MCI), a condition that may represent prodromal AD.

METHODS

A novel quantitative immunohistochemical approach was used to measure LR11 levels in brain tissue collected from subjects diagnosed antemortem with either no cognitive impairment, MCI, or AD from the Rush University Religious Orders Study.

RESULTS

LR11 levels in MCI were intermediate between no cognitive impairment and AD. LR11 expression was heterogeneous in MCI, forming low- and high-level LR11 subgroups. MCI subjects with low LR11 were significantly more cognitively impaired than the high LR11 subjects. We also found a significant correlation between cognitive performance and LR11 levels across all clinical groups examined. There was no association between LR11 and plaque and tangle pathology.

INTERPRETATION

Neuronal LR11 levels are reduced in prodomal AD. The correlation between LR11 expression and cognitive performance indicates that reduced LR11 levels reflect disease severity and may predict progression to AD in a subgroup of individuals with MCI.

Characterizing the memory changes in persons with mild cognitive impairment

Persons with mild cognitive impairment (MCI) do not meet criteria for Alzheimer's disease (AD) but are at high risk for developing the disease. Presence of a memory deficit is a key component in the characterization of MCI. This chapter presents empirical studies that attempt to describe and understand the nature of the memory deficit in MCI with a focus on episodic memory and working memory. Cross-sectional studies report prominent deficits of episodic memory characterized by impaired encoding of the contextual information that makes up complex events. This results in reduced free and cued recall, impaired recognition, and impaired associative learning. Although semantic encoding is found to be impaired in conditions that rely on explicit and intentional retrieval, preserved semantic processing is found with automatic conditions of testing. Studies indicate the presence of a partial deficit of working memory with the ability to divide attention being most severely impaired. However, there appears to be heterogeneity as to the extent of the working memory impairment. The presence of vascular anomalies on MRI, as well as being in a more advanced stage in the continuum from MCI to AD, are associated with more severe and more pervasive working memory deficits. Finally, longitudinal studies indicate that the combination of episodic and working memory deficits represents a strong predictor of progression from MCI to AD.

fMRI activation changes during successful episodic memory encoding and recognition in amnestic mild cognitive impairment relative to cognitively healthy older adults

BACKGROUND/AIMS

Previous functional MRI studies in individuals with amnestic mild cognitive impairment (AMCI), a putative, prodromal form of Alzheimer's disease, reveal substantial regional changes in brain activation during episodic memory function.

METHODS

Functional MRI was applied to examine changes in brain activation during different stages of episodic memory function using a subsequent memory task in individuals with AMCI relative to older normal controls.

RESULTS

We found that the AMCI group displayed greater activation in the right hippocampus but less activation in the frontal cortex relative to the older normal control group during intentional encoding of items that were subsequently recognized. We observed nearly the opposite pattern of results for successful recognition. The AMCI group displayed less activation in the medial temporal cortex but greater activation in the frontal cortex. In addition, the AMCI group showed reduced activation in the medial temporal and frontal cortices during incidental encoding of novel information during recognition.

CONCLUSION

The results of the present study suggest that brain activation differences in individuals with AMCI are modulated by the stage of episodic memory examined (i.e. intentional vs. incidental encoding vs. recognition). These observations may help to clarify some of the conflicting findings regarding brain activation changes in AMCI.

Nurses' role in identifying mild cognitive impairment in older adults

Mild cognitive impairment (MCI), a relatively new descriptive category, is believed to represent a stage between normal aging and early dementia. Nurse practitioners, who provide care for older adults across a variety of settings, are in a key position to detect early cognitive changes. The purpose of this study is to describe an approach to identifying MCI using a variety of measures and a consensus conference with neuropsychologists. The study was conducted in a sample of 130 elderly participants (aged 82.5 years; 81% female) residing in nursing homes, assisted living facilities, and senior housing. A team of clinicians (neuropsychologists and nurses) reviewed cognitive, mental health, and demographic data in consensus conference and classified study participants into 1 of 3 groups: cognitively intact (50.8%), amnestic MCI (19.2%), or probable dementia (30%). Discriminant function analysis (DFA) was used to independently classify individuals into cognitive status groups based on test scores alone and to compare quantitatively determined groups with consensus conference evaluations. The results indicate that the DFA correctly classified 95% of the participants. Further, results revealed a pattern in which persons with amnestic MCI have subtle memory impairments (similar to persons with dementia) but that more general cognitive functioning remains high (similar to intact persons). Nurse practitioners' heightened awareness of subtle distinctions in the dimensions of cognitive status associated with MCI can enhance their practice and assist them in making more informed referrals for dementia evaluations.

Mild cognitive dysfunction: an epidemiological perspective with an emphasis on African Americans

This review begins with a historical accounting of the evolution of the concept of mild cognitive dysfunction, including nomenclature and criteria from Kral to Petersen. A critical analysis of the main elements relating to assessment and diagnosis of mild cognitive dysfunction is provided. Methodological limitations in design, measurement, and characterization, especially as they relate to older African Americans, are identified. Data from a 15-year longitudinal study of community-dwelling African Americans in Indianapolis, Indiana, indicate a 23% prevalence of all-cause mild cognitive dysfunction, with approximately 25% progressing to dementia in 2 years and another 25% reverting to normal cognition in the same interval. Factors contributing to this longitudinal variability in outcomes are reviewed, including the role of medical health factors. The review closes with suggestions for next steps in the epidemiological research of mild cognitive impairment.

Repetition priming in aging and Alzheimer's disease: an integrative review and future directions

Two decades of research examining repetition priming in aging and Alzheimer's disease (AD) has yielded a large body of contradictory findings due to differences between studies in participant and task characteristics. Recent research that has employed methodological advances indicates that this form of implicit memory is preserved in healthy aging. When a priming deficit does occur in studies of aging, it is likely a very early signal of neurological disease. Future directions for research in this area include linking priming ability to known risk factors for development of AD, integrating priming measures into clinical neuropsychological assessment batteries, and implementing programs of cognitive retraining that enhance memory using stimulus repetition techniques.

Paradoxical upregulation of glutamatergic presynaptic boutons during mild cognitive impairment

Synaptic integrity is now recognized as a central component of Alzheimer's disease. Surprisingly, however, the structural status of glutamatergic synapses in Alzheimer's disease is unclear, despite the fact that glutamate is the major excitatory transmitter of the CNS and has key roles in excitotoxicity and long-term potentiation. The identification of specific markers of glutamatergic neurons now allows an assessment of the structural involvement of the glutamatergic system across progressive stages of the Alzheimer's pathology, an opportunity not afforded by previously used neurochemical approaches. Glutamatergic presynaptic bouton density and dystrophic neurite abundance were quantified in midfrontal gyrus brain tissue from subjects with no cognitive impairment, mild cognitive impairment, or mild- or severe-stage Alzheimer's disease. Our study demonstrates a striking pathology-dependent pattern of glutamatergic synaptic remodeling with disease progression. Subjects with mild cognitive impairment display a paradoxical elevation in glutamatergic presynaptic bouton density, a situation akin to that observed in the cholinergic system, which then depletes and drops with disease progression. This pattern of synaptic remodeling mirrors our previous findings in transgenic animal models and is of major relevance to current transmitter-based therapeutics.

Oxidative DNA damage in mild cognitive impairment and late-stage Alzheimer's disease

Increasing evidence supports a role for oxidative DNA damage in aging and several neurodegenerative diseases including Alzheimer's disease (AD). Attack of DNA by reactive oxygen species (ROS), particularly hydroxyl radicals, can lead to strand breaks, DNA–DNA and DNA–protein cross-linking, and formation of at least 20 modified bases adducts. In addition, α,β-unsaturated aldehydic by-products of lipid peroxidation including 4-hydroxynonenal and acrolein can interact with DNA bases leading to the formation of bulky exocyclic adducts. Modification of DNA bases by direct interaction with ROS or aldehydes can lead to mutations and altered protein synthesis. Several studies of DNA base adducts in late-stage AD (LAD) brain show elevations of 8-hydroxyguanine (8-OHG), 8-hydroxyadenine (8-OHA), 5-hydroxycytosine (5-OHC), and 5-hydroxyuracil, a chemical degradation product of cytosine, in both nuclear and mitochondrial DNA (mtDNA) isolated from vulnerable regions of LAD brain compared to age-matched normal control subjects. Previous studies also show elevations of acrolein/guanine adducts in the hippocampus of LAD subjects compared to age-matched controls. In addition, studies of base excision repair show a decline in repair of 8-OHG in vulnerable regions of LAD brain. Our recent studies show elevated 8-OHG, 8-OHA, and 5,6-diamino-5-formamidopyrimidine in both nuclear and mtDNA isolated from vulnerable brain regions in amnestic mild cognitive impairment, the earliest clinical manifestation of AD, suggesting that oxidative DNA damage is an early event in AD and is not merely a secondary phenomenon.

Alzheimer's disease and mild cognitive impairment

As our society ages, age-related diseases assume increasing prominence as both personal and public health concerns. Disorders of cognition are particularly important in both regards, and Alzheimer's disease is by far the most common cause of dementia of aging. In 2000, the prevalence of Alzheimer's disease in the United States was estimated to be 4.5 million individuals, and this number has been projected to increase to 14 million by 2050. Although not an inevitable consequence of aging, these numbers speak to the dramatic scope of its impact. This article focuses on Alzheimer's disease and the milder degrees of cognitive impairment that may precede the clinical diagnosis of probable Alzheimer's disease, such as mild cognitive impairment.

Mild cognitive impairment

Mild cognitive impairment refers to the transitional period between normal cognition and dementia, but is not an extension of normal ageing. Subjects with mild cognitive impairment have subtle but measurable cognitive impairment that is not severe enough to interfere with independent living or fulfil diagnosis criteria of dementia.

Cognitive impairment: classification and open issues

Several clinically-defined cognitive impairment syndromes, with differing diagnostic criteria and nomenclature, have been proposed to describe nondisabling symptomatic cognitive deficits. Incidence and prevalence rates vary as a result of different diagnostic criteria and sampling procedures across studies. The incidence rates of cognitive impairment increase with age; but no consistent data have been reported on the association with family history, age, sex, education, Apo E4 genotype, depression, and other traditional risk factors for dementia. Several studies have suggested that most patients with cognitive impairment clinically defined will progress to Alzheimer Disease (AD), but rates of conversion vary widely among studies. This review summarizes existing definitions and related epidemiological data.

Spatial reference and working memory across the lifespan of male Fischer 344 rats

Loss of mnemonic function is among the earliest and most disconcerting consequences of the aging process. This study was designed to provide a comprehensive profile of spatial mnemonic abilities in male Fischer 344 (F344) rats across the lifespan. Young, middle-aged, and aged F344 rats were trained in spatial reference and working memory versions of the water maze task. There was a progressive age-related decline in spatial reference memory across the lifespan. Reliable individual differences were observed among aged rats, with some aged rats performing as well as young cohorts and others performing outside this range. An age-related delay-dependent decline was observed on a working memory version of the water maze task although no relationship between performance on reference and working memory tasks was present. Notably, middle-aged rats were impaired relative to young on both tasks. Together these data demonstrate that individual differences in spatial reference memory exist among aged F344 rats and provide novel data demonstrating an unrelated decline in working memory across the lifespan, suggesting that age-related mnemonic dysfunction may occur across multiple brain systems.