Vascular risk factors in mild cognitive impairment subtypes. Findings from the ReGAl project

Cognitive testing following transient ischaemic attack: A systematic review of clinical assessment tools

Cognitive deficits are prevalent after transient ischaemic attack (TIA) and result in loss of function, poorer quality of life and increased risks of dependency and mortality. This systematic review aimed to synthesise the available evidence on cognitive assessment in TIA patients to determine the prevalence of cognitive deficits, and the optimal tests for cognitive assessment. Medline, Embase, PsychINFO and CINAHL databases were searched for relevant articles. Articles were screened by title and abstract. Full-text analysis and quality assessment was performed using the National Institute of Health Tool. Data were extracted on study characteristics, prevalence of TIA deficits, and key study findings. Due to significant heterogeneity, meta-analysis was not possible. Twenty-five full-text articles met the review inclusion criteria. There was significant heterogeneity in terms of cognitive tests used, definitions of cognitive impairment and TIA, time points post-event, and analysis methods. The majority of studies used the Mini-Mental State Examination (MMSE) or Montreal Cognitive Assessment (MoCA) (n = 23). Prevalence of cognitive impairment ranged from 2% to 100%, depending on the time-point and cognitive domain studied. The MoCA was more sensitive than the MMSE for identifying cognitive deficits. Deficits were common in executive function, attention, and language. No studies assessed diagnostic test accuracy against a reference standard diagnosis of cognitive impairment. Recommendations on cognitive testing after TIA are hampered by significant heterogeneity between studies, as well as a lack of diagnostic test accuracy studies. Future research should focus on harmonising tools, definitions, and time-points, and validating tools specifically for the TIA population.

Association between the frailty index and vascular brain damage: The Treviso Dementia (TREDEM) registry

PURPOSE

An association between frailty and vascular brain damage (VBD) has been described in older adults. However, most studies have identified frailty according to the phenotypic model. It is less clear whether frailty, operationalized as an accumulation of health deficits, is associated with the presence and severity of VBD. The present study was therefore undertaken to verify whether a 50-item frailty index (FI) is related to VBD in a large and relatively unselected cohort of attendees of a memory clinic.

MATERIALS AND METHODS

The TREDEM (Treviso Dementia) registry includes retrospective observational data of 1584 participants. A modified FI was calculated from 50 variables comprising diseases, disability, behavioral disorders, and blood biochemistry. The presence and severity of VBD, including leukoaraiosis, lacunes, larger infarctions and the hierarchical vascular rating scale (HVRS), were determined based on brain computerized tomography imaging. Multiple logistic regression models were built according to the stepwise method.

RESULTS

Mean age of the 1584 participants was 79.6 ± 7.5 years and 1033 (65.2 %) were females. The average number of health deficits was 11.6 ± 6.2, corresponding to an FI of 0.23 ± 0.12 (range: 0.00-0.56). Each 0.01-point increase in the FI was associated with an increased probability of leukoaraiosis (+2.3 %) and severe leukoaraiosis (+5 %), lacunas in the basal ganglia (+1.73 %), occipital lobes (+2.7 %), parietal lobes (+3 %), frontal lobes (+3.6 %), temporal lobes (+4.2 %), and thalamus (+4.4 %). Moreover, an increase of 0.01 points in the FI was associated with a 3.1 % increase in the probability of HVRS score (≥2).

CONCLUSION

An FI based on routine clinical and laboratory variables was associated with the presence, degree, and some localizations of VBD in a population of older adults with cognitive decline. This frailty assessment tool may therefore be used to identify individuals at risk of developing cerebrovascular disease and, consequently, to implement strategies for vascular risk factor control.

Association of Homocysteine Levels With Medial Temporal Lobe Atrophy Among Carriers and Non-carriers of APOE ε4 in MCI Subjects

BACKGROUND

Different clinical subtypes of mild cognitive impairment (MCI) involve heterogeneous underlying etiologies. This study investigated the association between demographics, neuropsychological performance, apolipoprotein E (APOE) genotype and magnetic resonance imaging (MRI) measures in patients with MCI (amnestic [aMCI] and non-amnestic [naMCI]).

METHODS

This case-control study included 130 aMCI patients, 58 naMCI patients, and 1,106 healthy controls (HCs). APOE genotypes, medial temporal lobe atrophy (MTA), neurological evaluation results, and white matter hyperintensities (WMH) were investigated. Serum folate and vitamin B12 concentrations were analyzed by radioimmunoassay, and plasma hyperhomocysteinemia (Hcy) was assessed by a high-performance liquid chromatography-fluorescence method.

RESULTS

Serum folate levels were significantly lower, but plasma Hcy levels were higher, in patients with aMCI and naMCI than in healthy controls. There were significantly higher MTA scores in the aMCI group than the healthy control group. Multiple linear regression showed that serum Hcy and folate concentrations were positively associated with MTA (p < 0.05), while APOE4 showed a significant negative association with MTA in the aMCI group (p < 0.01). In addition, moderate/severe WMH showed a significant negative association with MTA in the naMCI and HC groups (p < 0.01).

CONCLUSION

The combined presence of APOE4 and Hcy is associated with aMCI in elderly individuals, while moderate/severe WMH is related to naMCI, which suggests etiological differences across MCI subtypes.

Fornix Integrity Is Differently Associated With Cognition in Healthy Aging and Non-amnestic Mild Cognitive Impairment: A Pilot Diffusion Tensor Imaging Study in Thai Older Adults

Damage to the fornix leads to significant memory impairment and executive dysfunction and is associated with dementia risk. We sought to identify if fornix integrity and fiber length are disrupted in mild cognitive impairment (MCI) and how they associate with cognition. Data from 14 healthy older adult controls (HCs) and 17 subjects with non-amnestic MCI (n-aMCI) were analyzed. Diffusion tensor imaging (DTI) at 1.5 Tesla MRI was performed to enable manual tracing of the fornix and calculation of DTI parameters. Higher fractional anisotropy of body and column of the fornix was associated with better executive functioning and memory, more strongly in the HC than in the n-aMCI group. Fornix fiber tract length (FTL) was associated with better executive function, more strongly in the n-aMCI than in the HC group, and with better memory, more strongly in the HC than in the n-aMCI group. These results highlight a decline in the contributions of the fornix to cognition in n-aMCI and suggest that maintenance of fornix FTL is essential for sustaining executive functioning in people with n-aMCI.

Heterogeneity of Neuropsychological Impairment in HIV Infection: Contributions from Mild Cognitive Impairment

Despite longstanding acknowledgement of the heterogeneity of HIV-associated neurocognitive disorders (HAND), existing HAND diagnostic methods classify according to the degree of impairment, without regard to the pattern of neuropsychological strengths and weaknesses. Research in mild cognitive impairment (MCI) has demonstrated that classifying individuals into subtypes by both their level and pattern of impairment, using either conventional or statistical methods, has etiologic and prognostic utility. Methods for characterizing the heterogeneity of MCI provide a framework that can be applied to other disorders and may be useful in clarifying some of the current challenges in the study of HAND. A small number of studies have applied these methods to examine the heterogeneity of neurocognitive function among individuals with HIV. Most have supported the existence of multiple subtypes of neurocognitive impairment, with some evidence for distinct clinicodemographic features of these subtypes, but a number of gaps exist. Following a review of diagnostic methods and challenges in the study of HAND, we summarize the literature regarding conventional and empirical subtypes of MCI and HAND and identify directions for future research regarding neurocognitive heterogeneity in HIV infection.

Elevated rates of mild cognitive impairment in HIV disease

With the rising number of individuals in their 50s and 60s who are infected with HIV, concerns have emerged about possible increases in the rates of non-HIV-associated dementias. The current study examined the prevalence of mild cognitive impairment (MCI) in older HIV-infected adults, since MCI is an intermediate state between typical cognitive aging and dementia that emerges in this age range. Participants included 75 adults with HIV disease aged 50 years and older who were on combination antiretroviral therapy (cART) and had undetectable plasma viral loads and 80 demographically similar HIV-seronegative comparison subjects. Participants completed a research neuropsychological evaluation that was used to classify MCI according to the comprehensive diagnostic scheme described by Bondi et al. (J Alzheimers Dis 42:275-289, 2014). HIV-infected persons were over seven times more likely to have an MCI designation (16 %) than their seronegative counterparts (2.5 %). Within the HIV+ cohort, MCI had minimal overlap with diagnoses of asymptomatic neurocognitive impairment and was significantly associated with older age, lower Karnofsky Scale of Performance Scores, and mild difficulties performing instrumental activities of daily living (iADLs). HIV infection in older adults is associated with a notably elevated concurrent risk of MCI, which may increase the likelihood of developing non-HIV-associated dementias as this population ages further.

Cognitive performance after stroke--the Framingham Heart Study

BACKGROUND

Individuals with a high risk of stroke are also more prone to cognitive impairment perhaps because of concomitant vascular risk factors. In addition, clinical stroke increases the risk of subsequent dementia. Nevertheless, the relationship between clinical stroke and subsequent cognitive function in initially nondemented individuals remains less clear as most prior studies examined case series without controls.

AIMS

To specify among nondemented individuals the cognitive domains affected by clinical stroke, independently of vascular risk factors and prestroke cognition.

METHODS

One hundred thirty-two Framingham study participants (mean age = 77 ± 9 years, 54% women) with prospectively validated initial strokes, as well as age- and gender-matched controls, underwent identical cognitive evaluations ∼six-months after the stroke. Linear regression models were used to assess the differences in cognitive scores between stroke cases and controls adjusting for prestroke cognitive function as assessed by Mini-Mental State Examination scores, and with and without adjustment for vascular risk factors.

RESULTS

Adjusting for prestroke cognition and vascular risk factors, persons with stroke had poorer cognitive function in the domains of immediate recall of logical and visual memories (β = -1·27 ± 0·60, P = 0·035; β = -1·03 ± 0·47, P = 0·028, respectively), verbal learning (paired associate test; β = -1·31 ± 0·57, P = 0·023), language (Boston naming test; β = -0·27 ± 0·08, P = 0·002), executive function (digit span backward; β = -0·53 ± 0·21, P = 0·015), and visuospatial and motor skills (block design; β = -3·02 ± 1·06, P = 0·005).

CONCLUSIONS

Clinical stroke is associated with subsequent poorer performance in multiple cognitive domains. This association cannot be entirely explained by the individual's cognitive function prior to stroke or by concomitant vascular risk factor levels.

Proton MRS in mild cognitive impairment

Mild cognitive impairment (MCI) is a clinical syndrome operationalized for early diagnosis and treatment of Alzheimer's disease (AD). Many individuals with MCI are at the prodromal stage of AD or other dementia. Various quantitative magnetic resonance imaging (MRI) techniques that measure the anatomic, biochemical, microstructural, functional, and blood-flow changes are being evaluated as possible surrogate measures for early diagnosis and disease progression in MCI. The pathology underlying MCI is heterogeneous, dominated by AD, cerebrovascular disease, Lewy body disease, or a mixture of these pathologies in autopsy cohorts. Proton magnetic resonance spectroscopy ((1)H MRS) metabolite markers may help identify and track etiologies that typically underlie MCI in the elderly. The role of proton MRS will be critical for pathophysiological processes for which a reliable biomarker does not exist such as neuronal dysfunction, glial and microglial activation in MCI.

Magnetic resonance spectroscopy in common dementias

Neurodegenerative dementias are characterized by elevated myoinositol and decreased N-acetylaspartate (NAA) levels. The increase in myoinositol seems to precede decreasing NAA levels in Alzheimer's diseases. NAA/myo-inositol ratio in the posterior cingulate gyri decreases with increasing burden of Alzheimer's disease pathologic conditions. Proton magnetic resonance spectroscopy ((1)H MRS) is sensitive to the pathophysiologic processes associated with the risk of dementia in patients with mild cognitive impairment. Although significant progress has been made in improving the acquisition and analysis techniques in (1)H MRS, translation of these technical developments to clinical practice have not been effective because of the lack of standardization for multisite applications and normative data and an insufficient understanding of the pathologic basis of (1)H MRS metabolite changes.

Changes in mild cognitive impairment and its subtypes as seen on diffusion tensor imaging

BACKGROUND

Previous studies using diffusion tensor imaging (DTI) have observed microstructural abnormalities in white matter regions in both Alzheimer's disease and mild cognitive impairment (MCI). The aim of this work was to examine the abnormalities in white matter and subcortical regions of MCI and its subtypes in a large, community-dwelling older aged cohort.

METHODS

A community-based sample of 396 individuals without dementia underwent medical assessment, neuropsychiatric testing, and neuroimaging. Of these, 158 subjects were classified as MCI and 238 as cognitively normal (controls) based on international MCI consensus criteria. Regional fractional anisotropy (FA) and mean diffusivity (MD) measures were calculated from the DTI and compared between groups. The false discovery rate correction was applied for multiple testing.

RESULTS

Subjects with MCI did not have significant differences in FA compared with controls after correction for multiple testing, but had increased MD in the right putamen, right anterior limb of the internal capsule, genu and splenium of the corpus callosum, right posterior cingulate gyrus, left superior frontal gyrus, and right and left corona radiata. When compared with controls, changes in left anterior cingulate, left superior frontal gyrus, and right corona radiata were associated with amnestic MCI (aMCI), whereas changes in the right putamen, right anterior limb of the internal capsule, and the right corona radiata were associated with non-amnestic MCI (naMCI). On logistic regression, the FA values in the left superior gyrus and MD values in the anterior cingulate distinguished aMCI from naMCI.

CONCLUSIONS

MCI is associated with changes in white matter and subcortical regions as seen on DTI. Changes in some anterior brain regions distinguish aMCI from naMCI.

Cognitive impairment in nondemented oldest-old: prevalence and relationship to cardiovascular risk factors

OBJECTIVE

To determine the prevalence and types of cognitive impairment in a sample of nondemented participants aged ≥90 (the oldest-old) and to examine the relationships between cognitive impairment and cardiovascular risk factors.

PARTICIPANTS

The participants were 420 nondemented individuals from The 90+ Study, a study of aging and dementia in the oldest-old. These participants were categorized into four nonoverlapping groups: normal cognition, amnestic mild cognitive impairment (aMCI), nonamnestic MCI (naMCI), and other cognitive impairment (OCI). History of cardiovascular risk factors was assessed through self-report.

RESULTS

The overall prevalence of cognitive impairment in nondemented participants was 34.0% (95% CI: 29.5-38.5). The prevalence of OCI was highest (17.4%; 95% CI: 13.9-21.4), followed by aMCI (8.3%; 95% CI: 5.9-11.4) and naMCI (8.3%; 95% CI: 5.9-11.4). Normal cognition was present in 66.0% (95% CI: 61.2-70.5) of participants. History of hypertension and stroke were the only risk factors that varied between the groups, occurring more frequently in participants with naMCI (χ(2) = 3.82; P < .05) and OCI (χ(2) = 5.51; P < .05).

CONCLUSIONS

This study found a high prevalence of cognitive impairment in a sample of nondemented oldest-old. We did not find a strong relationship between cardiovascular risk factors and the cognitive impairment groups, other than between hypertension and naMCI and stroke and OCI. Future studies comparing the incidence of dementia in these groups will ultimately determine their predictive utility in the oldest-old.

Regional white matter hyperintensities in normal aging, single domain amnestic mild cognitive impairment, and mild Alzheimer's disease

Few studies have examined white matter hyperintensities (WMH) along the cognitive continuum between single-domain amnestic mild cognitive impairment (sd-aMCI) and Alzheimer's disease (AD). The aims of our study were to explore relationships between the extent and location of WMH and disease severity along the cognitive continuum and to determine whether differences in the distribution of WMH could be predictive of specific patterns of cognitive impairment. We compared cognitive function, vascular risk factors, and regional (frontal lobe, parieto-occipital [PO] lobe, temporal lobe, periventricular [PV] white matter and deep white matter) WMH volume in 37 patients with mild AD, 23 patients with sd-aMCI, and 24 age-matched and education-matched normal controls. A quantitative volumetric method was applied to measure WMH burden. Total and regional WMH burdens, except for those in the temporal lobe, were significantly correlated with age (p<0.01). We found a trend toward increasing WMH volume with disease severity, higher in AD than in sd-aMCI and lowest in the controls. Total WMH volume was associated with the global cognitive test score. In multiple linear regression analysis, PV WMH volume, but not deep WMH volume, strongly predicted performances on the Controlled Oral Word Association test and the Color Word Stroop test after adjusting for important demographic variables. Only PO WMH volume was a significant predictor of a cognitive test score when frontal and temporal WMH volumes were simultaneously entered into the regression model. The extent and distribution of WMH, especially in the PV and PO regions, were associated with disease severity and reduced cognition.

Subjective memory complaints, vascular risk factors and psychological distress in the middle-aged: a cross-sectional study

BACKGROUND

Subjective memory complaints (SMC) are common but their significance is still unclear. It has been suggested they are a precursor of mild cognitive impairment (MCI) or dementia and an early indicator of cognitive decline. Vascular risk factors have an important role in the development of dementia and possibly MCI. We therefore aimed to test the hypothesis that vascular risk factors were associated with SMC, independent of psychological distress, in a middle-aged community-dwelling population.

METHODS

A cross-sectional analysis of baseline data from the 45 and Up Study was performed. This is a cohort study of people living in New South Wales (Australia), and we explored the sample of 45, 532 participants aged between 45 and 64 years. SMC were defined as 'fair' or 'poor' on a self-reported five-point Likert scale of memory function. Vascular risk factors of obesity, diabetes, hypertension, hypercholesterolemia and smoking were identified by self-report. Psychological distress was measured by the Kessler Psychological Distress Scale. We tested the model generated from a randomly selected exploratory sample (n = 22, 766) with a confirmatory sample of equal size.

RESULTS

5, 479/45, 532 (12%) of respondents reported SMC. Using multivariate logistic regression, only two vascular risk factors: smoking (OR 1.18; 95% CI = 1.03 - 1.35) and hypercholesterolaemia (OR 1.19; 95% CI = 1.04 - 1.36) showed a small independent association with SMC. In contrast psychological distress was strongly associated with SMC. Those with the highest levels of psychological distress were 7.00 (95% CI = 5.41 - 9.07) times more likely to have SMC than the non-distressed. The confirmatory sample also demonstrated the strong association of SMC with psychological distress rather than vascular risk factors.

CONCLUSIONS

In a large sample of middle-aged people without any history of major affective illness or stroke, psychological distress was strongly, and vascular risk factors only weakly, associated with SMC, although we cannot discount psychological distress acting as a mediator in any association between vascular risk factors and SMC. Given this, clinicians should be vigilant regarding the presence of an affective illness when assessing middle-aged patients presenting with memory problems.

Should mild cognitive impairment be subtyped?

PURPOSE OF REVIEW

To review evidence on the validity and utility of recent approaches to subtyping late-life mild cognitive impairment.

RECENT FINDINGS

There is growing evidence that amnestic mild cognitive impairment is associated with biomarkers for Alzheimer's disease, while nonamnestic mild cognitive impairment maps more closely to cerebrovascular disease. The former is more likely to progress to dementia than the latter. Mild impairment in multiple cognitive domains appears to represent a more advanced disease state than single-domain impairment, and is more likely to progress to dementia. The cognitive subtypes have imprecise boundaries and have limited ecological validity. Approaches to subtyping that also incorporate biomarkers increase diagnostic specificity and have greater predictive value. However, these approaches have yet to be validated outside specialized memory clinic populations.

SUMMARY

Mild cognitive impairment as currently defined is still etiologically and prognostically heterogeneous, particularly outside specialty clinical settings. The objective of further subtyping is to delineate subgroups that are more clinically homogeneous. The current cognitive subtypes have some validity and utility but additional approaches should be explored so as to enhance these properties.

Metabolic syndrome, inflammation, and nonamnestic mild cognitive impairment in older persons: a population-based study

The metabolic syndrome (MetS) is more strongly associated with cognitive impairment in the presence of inflammation. This suggests that the association of MetS with mild cognitive impairment (MCI) may vary with the etiology and the subtype of MCI. This study investigated the association between MetS with or without inflammation and MCI [amnestic (a-MCI) and nonamnestic (na-MCI)]. We studied a randomly selected sample of 1969 participants (ages 70 to 89 y) from Olmsted County, MN, using the Clinical Dementia Rating Scale, a neurologic evaluation, and neuropsychologic testing. Data for participants were reviewed for a diagnosis of normal cognition, MCI, or dementia. Clinical components of MetS were ascertained by interview and confirmed from the medical records; biochemical measurements were assayed from a blood draw. We compared 88 na-MCI cases and 241 a-MCI cases with 1640 cognitively normal participants. MetS was not associated with either na-MCI or a-MCI. High C-reactive protein (CRP; highest tertile vs lowest tertile) was associated with na-MCI [odds ratio (OR)=1.85; 95% confidence interval (CI)=1.05, 3.24] but not with a-MCI, after adjusting for sex, age, and years of education. The combination of MetS and high CRP (compared to no MetS and lowest CRP tertile) was associated with na-MCI (OR=2.31; 95% CI=1.07, 5.00), but not with a-MCI (OR=0.96; 95% CI=0.59, 1.54). The combined presence of MetS and high levels of inflammation is associated with na-MCI in this elderly cohort, and suggests etiologic differences in MCI subtypes.

[Mild cognitive impairment]

Mild cognitive impairment (MCI) is a syndrome that spans the area between normal ageing and dementia. It is classified into amnestic and non-amnestic types, both with two subtypes: single domain and multiple domains. Prevalence of MCI depends on criteria and population and can vary from 0.1 to 42% persons of older age. In contrast to dementia, cognitive deterioration is less severe and activities of daily living are preserved. Most impaired higher cognitive functions in MCI are memory, executive functions, language, visuospatial functions, attention etc. Also there are depression, apathy or psychomotor agitation, and signs of psychosis. Aetiology of MCI is multiple, mostly neurodegenerative, vascular, psychiatric, internistic, neurological, traumatic and iatrogenic. Persons with amnestic MCI are at a higher risk of converting to Alzheimer's disease, while those with a single non-memory domain are at risk of developing frontotemporal dementia. Some MCI patients also progress to other dementia types, vascular among others. In contrast, some patients have a stationary course, some improve, while others even normalize. Every suspicion of MCI warrants a detailed clinical exploration to discover underlying aetiology, laboratory analyses, neuroimaging methods and some cases require a detailed neuropsychological assessment. At the present time there is no efficacious therapy for cognitive decline in MCI or the one that could postpone conversion to dementia. The treatment of curable causes, application of preventive measures and risk factor control are reasonable measures in the absence of specific therapy.

Differences in brain volume, hippocampal volume, cerebrovascular risk factors, and apolipoprotein E4 among mild cognitive impairment subtypes

OBJECTIVES

To evaluate demographics, magnetic resonance imaging (MRI) measures, and vascular risk among mild cognitive impairment (MCI) subtypes.

DESIGN

Cross-sectional study.

SETTING

Both clinics and the community.

PARTICIPANTS

A total of 153 subjects with MCI, 218 cognitively normal older individuals (controls), and 68 patients with Alzheimer disease.

MAIN OUTCOME MEASURES

Classification of subjects with MCI according to current subtype diagnostic convention based on neuropsychological performance, estimates of vascular risk based on medical history, research MRI unless there was a specific contraindication, and apolipoprotein E genotype.

RESULTS

Of the 153 subjects with MCI, 65 were diagnosed with amnestic single-domain, 46 with amnestic multiple-domain, 27 with nonamnestic single-domain, and 15 with nonamnestic multiple-domain MCI. Analyses of control, MCI, and Alzheimer disease cases revealed significant differences in brain and hippocampal volumes between each group. Post hoc analyses of MRI measures among the MCI subtypes found that patients with amnestic single-domain MCI had significantly less brain atrophy and that hippocampal volume differed significantly from controls for the 2 amnestic forms of MCI. Apolipoprotein E genotype prevalence was significantly greater in the amnestic and nonamnestic subtypes of MCI. Conversely, the nonamnestic subtypes were more likely to have increased vascular risk and to be African American.

CONCLUSIONS

Amnestic forms of MCI appear to have demographic, genetic, and MRI findings suggestive of Alzheimer disease pathology, whereas the nonamnestic forms of MCI have findings suggestive of vascular disease. Importantly, however, all subjects with MCI showed evidence of brain injury, and the biological differences among subtypes are relatively subtle beyond the memory vs nonmemory groupings.

Association of prior stroke with cognitive function and cognitive impairment: a population-based study

BACKGROUND

Defining the nature of the contribution of stroke to cognitive impairment remains challenging.

OBJECTIVE

To describe associations between stroke history, APOE genotype, and subtypes of mild cognitive impairment (MCI).

METHODS

We randomly selected residents from Olmsted County, Minnesota, aged 70 to 89 years on October 1, 2004, and invited eligible subjects without documented dementia to participate. Participants (n = 2050) were evaluated through an informant interview, a neurological evaluation, and neuropsychological testing. Neuropsychological testing included 9 tests to assess memory, attention, executive function, visuospatial cognition, and language. Subjects were diagnosed by consensus as cognitively normal or as having MCI (either amnestic or nonamnestic) or dementia. A history of stroke was obtained from the subjects and confirmed in their medical records. We computed the odds ratios (ORs) for a clinical diagnosis of MCI or for scoring in the lowest quartile on each cognitive domain.

RESULTS

There were 1640 cognitively normal subjects and 329 subjects with MCI: 241 with amnestic MCI and 88 with nonamnestic MCI. In fully adjusted models with only subjects without dementia, a history of stroke was associated with a higher OR of nonamnestic MCI (OR, 2.85; 95% confidence interval [CI], 1.61-5.04) than amnestic MCI (OR, 1.77; 95% CI, 1.14-2.74). A history of stroke was also associated with impaired function in each cognitive domain except memory. The association was strongest for attention and executive function (OR, 2.48; 95% CI, 1.73-3.53). APOE epsilon4 genotype was associated only with amnestic MCI and with impaired memory function.

CONCLUSIONS

In this population-based sample of persons without dementia, a history of stroke was particularly associated with nonamnestic MCI and impairment in nonmemory cognition. The APOE epsilon4 genotype was associated with memory impairment and amnestic MCI.

Hippocampal volumes, proton magnetic resonance spectroscopy metabolites, and cerebrovascular disease in mild cognitive impairment subtypes

BACKGROUND

Although a majority of patients with amnestic mild cognitive impairment (aMCI) progress to Alzheimer disease, the natural history of nonamnestic MCI (naMCI) is less clear. Noninvasive imaging surrogates for underlying pathological findings in MCI would be clinically useful for identifying patients who may benefit from disease-specific treatments at the prodromal stage of dementia.

OBJECTIVE

To determine the characteristic magnetic resonance imaging (MRI) and proton MR spectroscopy (1H MRS) profiles of MCI subtypes.

DESIGN

Case-control study.

SETTING

Community-based sample at a tertiary referral center.

PATIENTS

Ninety-one patients with single-domain aMCI, 32 patients with multiple-domain aMCI, 20 patients with single- or multiple-domain naMCI, and 100 cognitively normal elderly subjects frequency-matched by age and sex.

MAIN OUTCOME MEASURES

Posterior cingulate gyrus 1H MRS metabolite ratios, hippocampal volumes, and cerebrovascular disease on MRI.

RESULTS

Patients with single-domain aMCI were characterized by small hippocampal volumes and elevated ratios of myo-inositol to creatine levels. Patients with naMCI on average had normal hippocampal volumes and 1H MRS metabolite ratios, but a greater proportion (3 of 20 patients [15%]) had cortical infarctions compared with patients with single-domain aMCI (6 of 91 [7%]). For characterization of MCI subtypes, 1H MRS and structural MRI findings were complementary.

CONCLUSIONS

The MRI and 1H MRS findings in single-domain aMCI are consistent with a pattern similar to that of Alzheimer disease. Absence of this pattern on average in patients with naMCI suggests that cerebrovascular disease and other neurodegenerative diseases may be contributing to the cognitive impairment in many individuals with naMCI.

Contributions of neuropsychology and neuroimaging to understanding clinical subtypes of mild cognitive impairment

The original conceptualization of mild cognitive impairment (MCI) was primarily as an amnestic disorder representing an intermediate stage between normal aging and Alzheimer's dementia (AD). More recently, broader conceptualizations of MCI have emerged that also encompass cognitive domains other than memory. These characterizations delineate clinical subtypes that commonly include amnestic and non-amnestic forms, and that involve single and multiple cognitive domains. With the advent of these broader classifications, more specific information is emerging regarding the neuropsychological presentation of individuals with MCI, risk for dementia associated with different subtypes of MCI, and neuropathologic substrates connected to the clinical subtypes. This review provides an overview of this burgeoning literature specific to clinical subtypes of MCI. Focus is primarily on neuropsychological and structural neuroimaging findings specific to clinical subtypes of MCI as well as the issue of daily functioning. Although investigations of non-amnestic subtypes using advanced neuroimaging techniques and clinical trials are quite limited, we briefly review these topics in MCI because these data provide a framework for future investigations specifically examining additional clinical subtypes of MCI. Finally, the review comments on select methodological issues involved in studying this heterogeneous population, and future directions to continue to improve our understanding of MCI and its clinical subtypes are offered.

Coronary heart disease is associated with non-amnestic mild cognitive impairment

The progression of amnestic mild cognitive impairment (a-MCI) to Alzheimer's disease and hypothesized progression of non-amnestic mild cognitive impairment (na-MCI) to non-degenerative or vascular dementias suggest etiologic differences. We examined the association between coronary heart disease (CHD) and mild cognitive impairment (MCI) subtypes in a population-based cohort. Participants (n=1969; aged 70-89 years) were evaluated using the Clinical Dementia Rating Scale, a neurological examination, and neuropsychological testing for diagnoses of normal cognition, MCI, or dementia. CHD was defined as a history of myocardial infarction, angina, angiographic coronary stenosis, or coronary revascularization and ascertained by participant interview and from medical records. CHD was significantly associated with na-MCI (OR=1.93; 95% CI=1.22-3.06) but not with a-MCI (OR=0.94; 95% CI=0.69-1.28). In contrast, ApoE ɛ4 allele was significantly associated with a-MCI (OR=1.75; 95% CI=1.28-2.41), but not with na-MCI (OR=1.17; 95% CI=0.69-2.00). The association of CHD with prevalent na-MCI but not with a-MCI suggests that CHD and na-MCI may have similar underlying etiologies.

Stroke risk modifies regional white matter differences in mild cognitive impairment

Forty non-demented older adults who were divided into two groups on the basis of their cognitive status (MCI: n=20; normal control: n=20) underwent diffusion tensor imaging, and estimates of fractional anisotropy (FA) and mean diffusivity (MD) were obtained for the genu and splenium of the corpus callosum. Results demonstrated the following: (1) group comparisons revealed that splenium FA was significantly lower in MCI participants than in NC participants, despite no differences in gross morphometry or hippocampal volumes; (2) in the overall sample, higher stroke risk was associated with lower white matter integrity, particularly in the genu; (3) increased stroke risk was more strongly associated with poorer splenium FA in those with MCI than in normal elderly; (4) splenium FA significantly predicted performance on verbal memory (adjusting for the effects of age, education, and whole brain volume). Findings demonstrate a relationship between increased vascular burden and white matter changes, and they support the possibility that posterior white matter pathology may contribute to the development of MCI-related cognitive changes.