The MCI study in Taiwan

Veterans General Hospital started study for mild cognitive impairment (MCI) since 1996. We used clinical dementia rating (CDR) of 0.5 to define our questionable dementia (QD) subjects. These QD subjects received annual neuropsychological assessment in 5-year follow-up period. Annual conversion rate, apolipoprotein E (ApoE) genotype and neuropsychological risk factors for QD were investigated. We found a 19.9% person-year conversion rate for these QD subjects. Both of the poor cognitive performance and ApoE epsilon4 allele were risk factors for progressing to dementia. Based on the results of this study and the progress in the concept of MCI, we added more complex verbal and visual memory tests as well as MRI-based volumetry measurement in our subsequent research. Peterson's amnestic MCI criteria were used to diagnose our MCI subjects. In the 3-year follow-up period, the conversional rate was 18.2% person-year for MCI subjects, similar to our previous finding in QD. We found hippocampal volume was positively associated with cognitive performance. ApoE genotype had effect on hippocampal volume. Subjects with lower cognitive performance and smaller hippocampi had higher risk converting to AD. With rapidly expanding research on dementia and MCI worldwide, we are looking forward to seeing the integration in neurobiology, neuroimaging, and neurobehavior fields to establish a multidisciplinary approach to MCI and dementia.     

The rate of conversion of mild cognitive impairment to dementia: predictive role of depression

BACKGROUND: Mild cognitive impairment (MCI) is a condition referring to the persons with cognitive deficits measurable in some form or another, but not meeting criteria for dementia, and who have an increased risk of becoming demented. OBJECTIVE: To establish the rate of progression to dementia in MCI, to investigate the risk of conversion for amnestic vs multiple-domains subtypes, and to identify the predictors of progression. METHODS: MCI (n = 105) individuals enrolled in a longitudinal study received annual clinical and psychometric examinations for up to a mean of 3 years. The diagnosis of MCI according to Mayo Clinic Petersen's Criteria was conducted by a panel of specialists. RESULTS: After 3 years of follow-up, 23 of 105 subjects with MCI were diagnosed with dementia. 40 showed cognitive decline not dementia, 34 were stable and showed no cognitive decline or improvement, while eight showed cognitive improvement. CONCLUSIONS: We conclude that conversion rate from MCI to DSM-IIIR dementia was 21.9% over a period of 3 years. The occurrence of depressive symptoms may constitute a predictor for those who are more likely to progress to dementia. The risk of conversion to dementia was higher among the subjects with an evidence of impairment extending beyond memory than with those who suffered only from memory deficits, and the subjects who converted to dementia in this subtype had significantly higher baseline plasma total homocysteine levels than non-converters.     

Mild cognitive impairment: a cross-national comparison

OBJECTIVE: The main aim of this collaborative study was to assess the comparability of the most commonly used criteria for mild cognitive impairment (MCI) by comparing the cognitive performance of patients with MCI from the Mayo Clinic (USA) and the Karolinska Institutet (Sweden). METHODS: Standardised neuropsychological test scores were used to compare the two samples from the two institutions with regard to the number of cognitive domains in which performance was below 1.5 SD. Possible predictors for the conversion from MCI to Alzheimer's disease (AD) were assessed. RESULTS: When the two institutions were considered together in the Cox proportional hazard model, the number of affected cognitive domains below 1.5 SD was a significant predictor of time to AD diagnosis with age, education, and APOE epsilon4 genotype entered into the same model as covariates. The number of affected cognitive areas remained as a significant predictor when the institutions were considered separately. The logistic regression model of conversion to AD showed that only tests assessing learning and retention were predictors of developing AD. CONCLUSIONS: Differences in population as well as in methodology of case ascertainment as well as other aspects may account for the observed variability between samples of patients with MCI. The number of impaired cognitive factors at baseline can predict the progression from MCI to AD. Furthermore, tests assessing learning and retention are the best predictors for progression to AD.     

Clinical predictors of cognitive decline in patients with mild cognitive impairment: the Chongqing aging study

Mild cognitive impairment (MCI) is considered as the early stage of dementia which currently has no effective treatments. Reducing progression of cognitive decline at the MCI stage could be an important strategy for preventing conversion to dementia. The goal of this work was to screen for clinical predictors indicating the prognosis of MCI comprehensively; therefore, we assumed vascular risk factors (VRFs), carotid stenosis, and white matter changes (WMC) to be independent predictors. A total of 257 patients with MCI underwent collection of VRF information, neuropsychological evaluation, computed tomography angiography (CTA) to investigate carotid stenosis, and magnetic resonance imaging (MRI) to identify severity of WMC. After a 3-year follow-up period, the neuropsychological evaluation, CTA, and MRI were repeated to assess the progression of cognitive decline, carotid stenosis, and WMC. The conversion rate from MCI to dementia was 11.65% per year, and the conversion rate from MCI to Alzheimer's disease was 7.05% per year in our cohort. Cognitive decline (in terms of changes in Mini Mental State Examination scores) was associated with diabetes mellitus (p = 0.004), baseline WMC severity (p < 0.001), baseline carotid stenosis (p < 0.001), and WMC severity change (p < 0.001). Besides, diabetes, baseline WMC severity, baseline moderate-to-severe carotid stenosis, and carotid stenosis change during follow-up were predictors of conversion from MCI to dementia. Given the potential clinical predictors, our findings could imply that controlling blood glucose, removing carotid stenosis, and improving cerebral perfusion could be effective measures to delay cognitive decline in patients with MCI and prevent conversion from MCI to dementia.     

Neuropsychological prediction of conversion to Alzheimer disease in patients with mild cognitive impairment

CONTEXT: The likelihood of conversion to Alzheimer disease (AD) in mild cognitive impairment (MCI) and the "optimal" early markers of conversion need to be established. OBJECTIVES: To evaluate conversion rates to AD in subtypes of MCI and to identify neuropsychological measures most predictive of the time to conversion. DESIGN: Patients were followed up semiannually and controls annually. Subtypes of MCI were determined by using demographically adjusted regression norms on neuropsychological tests. Survival analysis was used to identify the most predictive neuropsychological measures. SETTING: Memory disorders clinic. PARTICIPANTS: One hundred forty-eight patients reporting memory problems and 63 group-matched controls. MAIN OUTCOME MEASURE: A consensus diagnosis of probable AD. RESULTS: At baseline, 108 patients met criteria for amnestic MCI: 87 had memory plus other cognitive domain deficits and 21 had pure memory deficits. The mean duration of follow-up for the 148 patients was 46.6 +/- 24.6 months. In 3 years, 32 (50.0%) of 64 amnestic-"plus" and 2 (10.0%) of 20 "pure" amnestic patients converted to AD (P = .001). In 148 patients, of 5 a priori predictors, the percent savings from immediate to delayed recall on the Selective Reminding Test and the Wechsler Adult Intelligence Scale-Revised Digit Symbol Test were the strongest predictors of time to conversion. From the entire neuropsychological test battery, a stepwise selection procedure retained 2 measures in the final model: total immediate recall on the Selective Reminding Test (odds ratio per 1-point decrease, 1.10; 95% confidence interval, 1.05-1.14; P < .0001) and Digit Symbol Test coding (odds ratio, 1.06; 95% confidence interval, 1.01-1.11; P = .01). The combined predictive accuracy of these 2 measures for conversion by 3 years was 86%. CONCLUSIONS: Mild cognitively impaired patients with memory plus other cognitive domain deficits, rather than those with pure amnestic MCI, constituted the high-risk group. Deficits in verbal memory and psychomotor speed/executive function abilities strongly predicted conversion to AD.     

Vascular risk factors and intensity of cognitive dysfunction in MCI

Patients with Mild Cognitive Impairment (MCI) have a greater risk of developing dementia than general population. Lots of evidence suggests that cardiovascular risk factors appear more often in the MCI than in general population The aim of this study was to evaluate association between cardiovascular risk factors and intensity of cognitive impairment in MCI patients. We evaluated 24 MCI patients (9 women and 15 men) fulfilling Mayo Clinic Group Criteria. Taking under consideration presence of cardiovascular diseases patients were divided into two groups: first group (n=16) MCI with cardiovascular diseases and second group (n=8) MCI without cardiovascular disorders. Cognitive functions were assessed by neuropsychological tests battery including MMSE, Clock Drawing Test, Trail Making Test (TMT), Verbal Fluency Test with letters FAS, Auditory Verbal Learning Test (AVLT). In the MCI group with vascular risk factors we have found more distinct dysfunction of learning new information, recall and short-term memory than in MCI patients without vascular pathology. In conclusion we may suggest that more distinct cognitive deficit may indicate higher risk of developing dementia, that is why patients with MCI should be under special supervision, with at least annual neuropsychological evaluation.     

Defining optimal cutoff scores for cognitive impairment using Movement Disorder Society Task Force criteria for mild cognitive impairment in Parkinson's disease

The recently proposed Movement Disorder Society (MDS) Task Force diagnostic criteria for mild cognitive impairment in Parkinson's disease (PD‐MCI) represent a first step toward a uniform definition of PD‐MCI across multiple clinical and research settings. However, several questions regarding specific criteria remain unanswered, including optimal cutoff scores by which to define impairment on neuropsychological tests. Seventy‐six non‐demented PD patients underwent comprehensive neuropsychological assessment and were classified as PD‐MCI or PD with normal cognition (PD‐NC). The concordance of PD‐MCI diagnosis by MDS Task Force Level II criteria (comprehensive assessment), using a range of standard deviation (SD) cutoff scores, was compared with our consensus diagnosis of PD‐MCI or PD‐NC. Sensitivity, specificity, and positive and negative predictive values were examined for each cutoff score. PD‐MCI subtype classification and distribution of cognitive domains impaired were evaluated. Concordance for PD‐MCI diagnosis was greatest for defining impairment on neuropsychological tests using a 2 SD cutoff score below appropriate norms. This cutoff also provided the best discriminatory properties for separating PD‐MCI from PD‐NC compared with other cutoff scores. With the MDS PD‐MCI criteria, multiple domain impairment was more frequent than single domain impairment, with predominant executive function, memory, and visuospatial function deficits. Application of the MDS Task Force PD‐MCI Level II diagnostic criteria demonstrates good sensitivity and specificity at a 2 SD cutoff score. The predominance of multiple domain impairment in PD‐MCI with the Level II criteria suggests not only influences of testing abnormality requirements, but also the widespread nature of cognitive deficits within PD‐MCI. © 2013 International Parkinson and Movement Disorder Society     

An investigation of PreMCI: subtypes and longitudinal outcomes

Background/AimsTo investigate the clinical features and rates of progression of conditions that are not considered to be normal, but do not fulfill criteria for mild cognitive impairment (MCI).MethodsWe longitudinally evaluated 269 elderly subjects who did not meet formal criteria for MCI at baseline but had: (1) a clinical history suggesting MCI without neuropsychological deficits (PreMCI-Clinical); or (2) neuropsychological deficits on one or more memory measures in conjunction with a negative clinical examination (amnestic PreMCI-NP) or were normal on both neuropsychological and clinical examination.ResultsThe rate of progression to MCI or dementia over an average of 2- to 3 years was 3.7% for no cognitive impairment subjects, whereas it was significantly greater for all PreMCI subtypes (22.0% for PreMCI-Clinical, 38.9% for amnestic PreMCI-NP subjects with two or more memory impairments). Among PreMCI subjects as a whole, lower baseline scores on object memory and category fluency tests were the best predictors of progression to MCI or dementia. Cardiovascular risk factors, Parkinsonian symptoms, and hippocampal atrophy were not associated with progression.ConclusionDistinct PreMCI subtypes defined on the basis of clinical and neuropsychological evaluations were found to have distinct characteristics, but both subtypes demonstrated elevated risk for progression to MCI or dementia. Despite the lack of evidence of clinical impairment, subjects with neuropsychological deficits in two memory domains were particularly at increased risk for progression of their deficits.     

Conversion of mild cognitive impairment to dementia: predictive role of mild cognitive impairment subtypes and vascular risk factors

Mild cognitive impairment (MCI) is regarded as a precursor to dementia, but not all patients with MCI develop dementia. We followed up 165 elderly outpatients with MCI for a mean of 3 years. The aims were (1) to investigate the risk of conversion to dementia for different MCI subtypes diagnosed according to standardized criteria (amnestic; impairment of memory plus other cognitive domains; nonamnestic); (2) to assess whether the risk of conversion was affected by several established and emerging vascular risk factors. Forty-eight subjects (29%) converted to dementia, and the risk of conversion was doubled for amnestic MCI with respect to the other subtypes. Independently of MCI subtype, risk of conversion was associated with atrial fibrillation and low serum folate levels. Our results show that current diagnostic criteria for MCI define heterogeneous populations, but some potentially treatable vascular risk factors may be of help in predicting conversion to dementia.     

Preclinical dementia: an Italian multicentre study on amnestic mild cognitive impairment

BACKGROUND: Different rates and cognitive predictors of conversion to dementia have been reported in subjects with different kinds of mild cognitive impairment (MCI). METHODS: A prospective, 24-month follow-up study, involving 269 subjects who strictly fulfilled criteria for the amnestic MCI. RESULTS: Conversion rate to dementia was 21.4% per year. Seventy-nine out of the 83 individuals who developed dementia were affected by probable Alzheimer's disease (AD). Among others, at the 24-month follow-up 24.1% were still affected by amnestic MCI, 13.3% had changed their neuropsychological profile of impairment and 17.2% were cognitively normalised. Compared to subjects who did not convert to AD, those who did convert showed poorer immediate and delayed recall and recognition of verbal and visual material at baseline as well as reduced executive abilities. A combination of age, Clinical Dementia Rating boxes and scores on delayed recall and recognition of verbal and visual material accurately identified 86% of the subjects who developed AD. CONCLUSIONS: Elderly subjects affected by an isolated memory disorder have a high probability of developing AD. The ability of verbal and visual measures to predict incipient dementia of memory impairment may be increased by the simultaneous assessment of individual features, such as age or rate of functional impairment.     

A voxel based morphometry study on mild cognitive impairment

BACKGROUND: Mild cognitive impairment (MCI) is the most widely used concept in classifying cognitive impairment in the elderly who do not fulfil the criteria for dementia. MCI is considered to confer an increased risk of progressing to dementia and most often Alzheimer's disease (AD). Various approaches such as imaging of the brain have been applied to predict the conversion of MCI to dementia. A number of volumetric magnetic resonance imaging (MRI) studies have detected atrophy of the medial temporal lobe in subjects with MCI, but for the other cerebral regions the results have been inconsistent. OBJECTIVE: To study the pattern of brain atrophy in MCI. METHODS: Thirty two controls and 51 individuals with MCI deriving from population based cohorts were studied by MRI using voxel based morphometry. The threshold of t maps was set at p < 0.001. RESULTS: Individuals with MCI had significant unilateral atrophy in the medial temporal lobe on the right side. Less extensive atrophy was found elsewhere-for example, in the temporal lobe, left superior parietal lobule, left anterior cingulate gyrus, and bilaterally in the thalami. CONCLUSIONS: The MRI findings in MCI resemble those seen in early AD.     

Dementia, asymmetry of temporal lobe structures, and apolipoprotein E genotype: relationships to cerebral atrophy and neuropsychological impairment.

We examined asymmetry of hippocampal volume as well as other temporal lobe structures (temporal lobe, temporal horn of the lateral ventricular system, parahippocampal and fusiform gyri) in 194 subjects from the Cache County, Utah study, with varying disorders [85 with Alzheimer's disease (AD), 59 with some cognitive or neuropsychiatric disorder-referenced as a Mixed Neuropsychiatric group, 30 with mild ambiguous/mild cognitive impairment (MA/MCI) and 20 controls] and APOE genotypes. Asymmetry was determined by subtracting left-side volume from the right corrected by total intracranial volume. No significant asymmetry was observed to be associated with presence of the epsilon4 allele. Since the AD-epsilon4 allele risk effect may be expressed early in the course of the disorder, we also examined asymmetry indices in AD, MA/MCI and Mixed Neuropsychiatric subjects early in the course of their disorder (2 years or less) to those with longer duration illness (greater than 2 years). We observed a leftward asymmetry (i.e., left side larger) regardless of APOE genotype in hippocampal volume where both AD and MCI subjects demonstrated a leftward shift in hippocampal size when length of disease (LOD) was less but not more than 2 years. Leftward asymmetry was not associated with LOD in the Mixed Neuropsychiatric group. These findings do not support an association between epsilon4 and hippocampal asymmetry in dementia. We also examined whether asymmetry influenced neuropsychological performance, but minimal effects were observed. Where significance or strong trends were observed, better neuropsychological performance was associated with larger parenchymal volume of temporal lobe structures. These findings were interpreted as representing cognitive reserve effects where larger volume was protective against impairment. The role of asymmetry research in understanding neuropsychological performance in dementia is discussed.     

The new Alzheimer’s criteria in a naturalistic series of patients with mild cognitive impairment

To test the validity of the new diagnostic criteria for Alzheimer’s disease (AD) in a naturalistic series of patients with mild cognitive impairment (MCI). Ninety consecutive MCI patients were enrolled in a longitudinal study on the natural history of cognitive impairment. Medial temporal (MT) atrophy on MRI was defined as hippocampal volume below the fifth percentile of the distribution in healthy elders, abnormal CSF was based on Sjogren’s cutoffs for Abeta42 and tau, and temporoparietal hypometabolism on 18F-FDG PET based on Herholz’s t sum score. Patients were followed clinically to detect conversion to AD (MCI-AD), non-AD dementia (MCI-nAD), or no conversion (MCI-NC). The 24 MCI-AD and 15 MCI-nAD patients had sociodemographic, clinical, and neuropsychological baseline features similar to the 51 MCI-NC patients. All MCI patients with MT atrophy converted to AD, as did all those with abnormal CSF, but only 48 and 35% of those without MT atrophy or abnormal CSF converted (p on logrank test = 0.0007 and 0.001). Prediction of AD conversion was enhanced when positivity to either MT atrophy or abnormal CSF was considered, with only 15% of those MCI patients negative on both converting to AD (p < 0.0005). Markers were not predictive of non-AD dementia conversion. The accuracy of either MT atrophy or abnormal CSF in discriminating MCI-AD from MCI-NC was good (AUC 0.82, 95% CI 0.70–0.95). MT atrophy and abnormal CSF are the single most robust predictors of conversion to AD in MCI patients, and their combination enhances prediction. AD markers are not predictive of conversion to non-AD dementia.     

Neuropsychiatric symptoms in older people with and without cognitive impairment

Neuropsychiatric symptoms (NPS) are non-cognitive disturbances such as depression. Rates of NPS have been shown to increase as cognitive ability declines and may be useful in predicting transition from mild cognitive impairment (MCI) to dementia. This community-based study reports the association between NPS and cognitive decline over two years. Participants included 873 community dwelling adults aged 70-90 years enrolled in the Sydney Memory and Ageing Study. NPS were assessed by the Neuropsychiatric Inventory (NPI). Cognitive impairment was defined by diagnosis (MCI or incident dementia) or neuropsychological test performance across five cognitive domains. Cognitive decline was defined by progression to dementia or worse neuropsychological performance. Total NPS at baseline did not differ between those without cognitive impairment (26.2%) and those with MCI (28.8%), but agitation and apathy were associated with MCI. Only baseline depression was associated with dementia at follow-up. Total NPS at baseline was cross-sectionally associated with cognitive impairment in executive function, attention, and global cognition, but did not predict cognitive decline. Depression, anxiety, agitation, anxiety, and apathy were all associated with impairment in at least one cognitive domain, but only anxiety and agitation were significantly associated with cognitive decline. Sensitivity analyses applied more stringent criteria for NPS and cognitive impairment in MCI but did not alter interpretation of results from the main analysis. Overall rates of NPS at baseline were not associated with MCI, dementia, or cognitive decline over two years. Additional follow-up is needed to further examine this association over a longer time course.     

Neuropathologic outcome of mild cognitive impairment following progression to clinical dementia

BACKGROUND: The pathologic outcome of patients diagnosed with mild cognitive impairment (MCI) following progression to dementia is poorly understood. OBJECTIVE: To determine the pathologic substrates of dementia in cases with prior diagnosis of amnestic MCI. DESIGN AND SETTING: Community-based cohort. PATIENTS: Thirty-four subjects followed up prospectively as part of a community-based study who were diagnosed with amnestic MCI, progressed to clinical dementia, and underwent subsequent postmortem brain analysis. MAIN OUTCOME MEASURES: Neuropathologic analyses resulted in assignment of a primary pathologic diagnosis and included staging of Alzheimer pathologic abnormalities and identification of contributing vascular disease, Lewy bodies, and argyrophilic grains. RESULTS: Although the majority of subjects progressed both clinically and pathologically to Alzheimer disease (AD), 10 (29%) of them developed non-AD primary pathologic abnormalities. All of the cases were found to have sufficient pathologic abnormalities in mesial temporal lobe structures to account for their amnestic symptoms regardless of the cause. Most subjects were found to have secondary contributing pathologic abnormalities in addition to primary pathologic diagnoses. No significant differences between subjects with and without neuropathologically proven AD were detected in demographic variables, apolipoprotein E genotype, or cognitive test measures at onset of MCI, onset of dementia, or last clinical evaluation. CONCLUSIONS: The neuropathologic outcome of amnestic MCI following progression to dementia is heterogeneous, and it includes AD at a high frequency. Complex neuropathologic findings including 2 or more distinct pathologic entities contributing to dementia may be common in community-based cohorts. Neither demographic variables nor cognitive measures had predictive value in determining which patients diagnosed with MCI will develop the neuropathologic features of AD.     

Classification criteria for mild cognitive impairment: a population-based validation study

OBJECTIVE: To evaluate the predictive validity and temporal stability of diagnostic criteria for mild cognitive impairment (MCI). BACKGROUND: MCI has been proposed as a nosologic entity referring to elderly persons with subclinical cognitive deficits due to incipient dementia. Classification criteria, which have been derived from small, selected clinical groups, are currently disputed, and have not yet been assessed within the general population. METHODS: Subjects meeting current criteria for MCI and also age-associated cognitive decline (AACD-a similar concept that is assumed to be related to normal cognitive aging processes rather than incipient dementia) were identified within each of three waves of a longitudinal population study, which included a standardized neurologic examination. RESULTS: In the general population, the prevalence of MCI was estimated to be 3.2% and AACD 19.3%. MCI was a poor predictor of dementia within a 3-year period, with an 11.1% conversion rate. Subjects with MCI also constituted an unstable group, with almost all subjects changing category each year. Discriminant function analysis failed to isolate a homogeneous clinical group. Subjects classified as AACD, contrary to the theoretical assumptions underlying the disorder, represented a more stable group, with a 28.6% conversion rate to dementia over 3 years (relative risk = 21.2). CONCLUSION: MCI criteria perform poorly when applied to a representative population sample. The authors propose modifications to current diagnostic criteria to increase their capacity to detect incipient dementia.     

Persistent mild cognitive impairment in geriatric depression

BACKGROUND: Cognitive impairment often occurs with geriatric depression and impairments may persist despite remission of depression. Although clinical definitions of mild cognitive impairment (MCI) have typically excluded depression, a neuropsychological model of MCI in depression has utility for identifying individuals whose cognitive impairments may persist or progress to dementia. METHODS: At baseline and 1-year follow-up, 67 geriatric patients with depression had a comprehensive clinical examination that included depression assessment and neuropsychological testing. We defined MCI by a neuropsychological algorithm and examined the odds of MCI classification at Year 1 for remitted depressed individuals with baseline MCI, and examined clinical, functional and genetic factors associated with MCI. RESULTS: Fifty-four percent of the sample had MCI at baseline. Odds of MCI classification at Year 1 were four times greater among patients with baseline MCI than those without. Instrumental activities of daily living were associated with MCI at Year 1, while age and APOE genotype was not. CONCLUSIONS: These results confirm previous observations that MCI is highly prevalent among older depressed adults and that cognitive impairment occurring during acute depression may persist after depression remits. Self-reported decline in functional activities may be a marker for persistent cognitive impairment, which suggests that assessments of both neuropsychological and functional status are important prognostic factors in the evaluation of geriatric depression.     

Mild cognitive impairment: a clinically useful but currently ill-defined concept?

The term mild cognitive impairment (MCI) has gained wide currency among clinicians, and particularly dementia researchers, to denote patients with memory deficits who do not yet fulfil the criteria for dementia, but are at high risk of conversion. MCI is therefore regarded as the prodromic or pre-dementia stage of Alzheimer's disease. The accurate categorization of these subjects has far-reaching implications, both for research in this field and for those individuals who fall within this diagnostic group. Despite a wealth of studies examining the neuropsychological, neuroimaging and biological profiles of this population, the characterization of MCI remains controversial. This brief overview discusses a number of the issues related to this topic and questions the currently accepted criteria.     

The Impact of Deep Dysgraphia on Graphemic Buffer Disorders

The term mild cognitive impairment (MCI) has gained wide currency among clinicians, and particularly dementia researchers, to denote patients with memory deficits who do not yet fulfil the criteria for dementia, but are at high risk of conversion. MCI is therefore regarded as the prodromic or pre-dementia stage of Alzheimer’s disease. The accurate categorization of these subjects has far-reaching implications, both for research in this field and for those individuals who fall within this diagnostic group. Despite a wealth of studies examining the neuropsychological, neuroimaging and biological profiles of this population, the characterization of MCI remains controversial. This brief overview discusses a number of the issues related to this topic and questions the currently accepted criteria.     

Effects of varying diagnostic criteria on prevalence of mild cognitive impairment in a community based sample

Mild cognitive impairment (MCI) is proposed to be a prodrome to dementia in some older adults. However, the presentation of MCI in the community can differ substantially from clinic-based samples. The aim of the current study is to demonstrate the effects of different operational definitions of MCI on prevalence estimates in community-dwelling older adults. A consecutive series of 200 participants aged 65 and over from the Adult Changes in Thought (ACT) community-based cohort were approached to undergo comprehensive neuropsychological and medical evaluation; 159 were included in the final analyses. Nondemented subjects were categorized using various diagnostic criteria for MCI. In a novel approach, neuropsychological test scores were evaluated using an individualized benchmark as a point of test comparison, as well as traditional methods that entail comparison to age-based normative data. Diagnostic criteria were further subdivided by severity of impairment (1.0 vs. 1.5 standard deviations [sd] below the benchmark) and extent of impairment (based on a single test or an average of tests within a cognitive domain). MCI prevalence rates in the sample were highly dependent on these diagnostic factors, and varied from 11% to 92% of the sample. Older groups tended to show higher prevalence rates, although this was not the case across all diagnostic schemes. The use of an individualized benchmark, less severe impairment cutoff, and impairment on only a single test all produced higher rates of MCI. Longitudinal follow-up will determine whether varying diagnostic criteria improves sensitivity and specificity of the MCI diagnosis as a predictor for dementia.