Visual associative learning to detect early episodic memory deficits and distinguish Alzheimer's disease from other types of dementia.

OBJECTIVE: We investigated how well a visual associative learning task discriminates Alzheimer's disease (AD) dementia from other types of dementia and how it relates to AD pathology. METHODS: 3,599 patients (63.9 ± 8.9 years old, 41% female) from the Amsterdam Dementia Cohort completed two sets of the Visual Association Test (VAT) in a single test session and underwent magnetic resonance imaging. We performed receiver operating curve analysis to investigate the VAT's discriminatory ability between AD dementia and other diagnoses and compared it to that of other episodic memory tests. We tested associations between VAT performance and medial temporal lobe atrophy (MTA), and amyloid status (n = 2,769, 77%). RESULTS: Patients with AD dementia performed worse on the VAT than all other patients. The VAT discriminated well between AD and other types of dementia (area under the curve range 0.70-0.86), better than other episodic memory tests. Six-hundred forty patients (17.8%) learned all associations on VAT-A, but not on VAT-B, and they were more likely to have higher MTA scores (odds ratios range 1.63 (MTA 0.5) through 5.13 for MTA ≥ 3, all p < .001) and to be amyloid positive (odds ratio = 3.38, 95%CI = [2.71, 4.22], p < .001) than patients who learned all associations on both sets. CONCLUSIONS: Performance on the VAT, especially on a second set administered immediately after the first, discriminates AD from other types of dementia and is associated with MTA and amyloid positivity. The VAT might be a useful, simple tool to assess early episodic memory deficits in the presence of AD pathology.

The identification of cognitive subtypes in Alzheimer's disease dementia using latent class analysis.

OBJECTIVE: Alzheimer's disease (AD) is a heterogeneous disorder with complex underlying neuropathology that is still not completely understood. For better understanding of this heterogeneity, we aimed to identify cognitive subtypes using latent class analysis (LCA) in a large sample of patients with AD dementia. In addition, we explored the relationship between the identified cognitive subtypes, and their demographical and neurobiological characteristics. METHODS: We performed LCA based on neuropsychological test results of 938 consecutive probable patients with AD dementia using Mini-Mental State Examination as the covariate. Subsequently, we performed multinomial logistic regression analysis with cluster membership as dependent variable and dichotomised demographics, APOE genotype, cerebrospinal fluid biomarkers and MRI characteristics as independent variables. RESULTS: LCA revealed eight clusters characterised by distinct cognitive profile and disease severity. Memory-impaired clusters-mild-memory (MILD-MEM) and moderate-memory (MOD-MEM)-included 43% of patients. Memory-spared clusters mild-visuospatial-language (MILD-VILA), mild-executive (MILD-EXE) and moderate-visuospatial (MOD-VISP) -included 29% of patients. Memory-indifferent clusters mild-diffuse (MILD-DIFF), moderate-language (MOD-LAN) and severe-diffuse (SEV-DIFF) -included 28% of patients. Cognitive clusters were associated with distinct demographical and neurobiological characteristics. In particular, the memory-spared MOD-VISP cluster was associated with younger age, APOE e4 negative genotype and prominent atrophy of the posterior cortex. CONCLUSIONS: Using LCA, we identified eight distinct cognitive subtypes in a large sample of patients with AD dementia. Cognitive clusters were associated with distinct demographical and neurobiological characteristics.

The behavioural/dysexecutive variant of Alzheimer's disease: clinical, neuroimaging and pathological features.

A 'frontal variant of Alzheimer's disease' has been described in patients with predominant behavioural or dysexecutive deficits caused by Alzheimer's disease pathology. The description of this rare Alzheimer's disease phenotype has been limited to case reports and small series, and many clinical, neuroimaging and neuropathological characteristics are not well understood. In this retrospective study, we included 55 patients with Alzheimer's disease with a behavioural-predominant presentation (behavioural Alzheimer's disease) and a neuropathological diagnosis of high-likelihood Alzheimer's disease (n = 17) and/or biomarker evidence of Alzheimer's disease pathology (n = 44). In addition, we included 29 patients with autopsy/biomarker-defined Alzheimer's disease with a dysexecutive-predominant syndrome (dysexecutive Alzheimer's disease). We performed structured chart reviews to ascertain clinical features. First symptoms were more often cognitive (behavioural Alzheimer's disease: 53%; dysexecutive Alzheimer's disease: 83%) than behavioural (behavioural Alzheimer's disease: 25%; dysexecutive Alzheimer's disease: 3%). Apathy was the most common behavioural feature, while hyperorality and perseverative/compulsive behaviours were less prevalent. Fifty-two per cent of patients with behavioural Alzheimer's disease met diagnostic criteria for possible behavioural-variant frontotemporal dementia. Overlap between behavioural and dysexecutive Alzheimer's disease was modest (9/75 patients). Sixty per cent of patients with behavioural Alzheimer's disease and 40% of those with the dysexecutive syndrome carried at least one APOE ε4 allele. We also compared neuropsychological test performance and brain atrophy (applying voxel-based morphometry) with matched autopsy/biomarker-defined typical (amnestic-predominant) Alzheimer's disease (typical Alzheimer's disease, n = 58), autopsy-confirmed/Alzheimer's disease biomarker-negative behavioural variant frontotemporal dementia (n = 59), and controls (n = 61). Patients with behavioural Alzheimer's disease showed worse memory scores than behavioural variant frontotemporal dementia and did not differ from typical Alzheimer's disease, while executive function composite scores were lower compared to behavioural variant frontotemporal dementia and typical Alzheimer's disease. Voxel-wise contrasts between behavioural and dysexecutive Alzheimer's disease patients and controls revealed marked atrophy in bilateral temporoparietal regions and only limited atrophy in the frontal cortex. In direct comparison with behavioural and those with dysexecutive Alzheimer's disease, patients with behavioural variant frontotemporal dementia showed more frontal atrophy and less posterior involvement, whereas patients with typical Alzheimer's disease were slightly more affected posteriorly and showed less frontal atrophy (P < 0.001 uncorrected). Among 24 autopsied behavioural Alzheimer's disease/dysexecutive Alzheimer's disease patients, only two had primary co-morbid FTD-spectrum pathology (progressive supranuclear palsy). In conclusion, behavioural Alzheimer's disease presentations are characterized by a milder and more restricted behavioural profile than in behavioural variant frontotemporal dementia, co-occurrence of memory dysfunction and high APOE ε4 prevalence. Dysexecutive Alzheimer's disease presented as a primarily cognitive phenotype with minimal behavioural abnormalities and intermediate APOE ε4 prevalence. Both behavioural Alzheimer's disease and dysexecutive Alzheimer's disease presentations are distinguished by temporoparietal-predominant atrophy. Based on the relative sparing of frontal grey matter, we propose to redefine these clinical syndromes as 'the behavioural/dysexecutive variant of Alzheimer's disease' rather than frontal variant Alzheimer's disease. Further work is needed to determine whether behavioural and dysexecutive-predominant presentations of Alzheimer's disease represent distinct phenotypes or a single continuum.

Early onset APOE E4-negative Alzheimer's disease patients show faster cognitive decline on non-memory domains.

Age at onset and APOE E4-genotype have been shown to influence clinical manifestation of Alzheimer's disease (AD). We investigated rate of decline in specific cognitive domains according to age at onset and APOE E4-genotype in patients with AD. 199 patients with probable AD underwent at least two annual neuropsychological assessments. Patients were classified according to age-at-onset (≤ 65 years vs >65 years) and APOE genotype (positive vs negative). The neuropsychological test battery compromised tests for memory, language, attention, executive and visuo-spatial functioning. For each domain compound z-scores were calculated, based on the baseline performance of patients. Average duration of follow-up was 1.5 ± 1 years. We used linear mixed models (LMM) to estimate effects of age, APOE and age⁎APOE on cognitive decline over time. At baseline, patients were 65 ± 8 years, 98(49%) were female and MMSE was 22 ± 4. LMM showed that early onset patients declined faster on executive functioning (ß ± SE:-0.09 ± 0.06) than late onset patients, but age was not related to decline in the other cognitive domains. APOE E4 negative patients declined faster on language than APOE E4 positive patients (ß ± SE:-0.1 ± 0.06). When we took age and APOE genotype into account simultaneously, we found that compared to late onset-E4 positive patients, early onset-E4 negative patients declined faster on language (ß ± SE:-0.36 ± 0.1), attention (ß ± SE:-0.42 ± 0.1), executive (ß ± SE:-0.41 ± 0.1) and visuo-spatial functioning (ß ± SE:-0.43 ± 0.1). Late onset-E4 negative and early onset-E4 positive patients showed intermediate rates of decline. We found no differences in decline on memory. We found that patients who develop AD despite absence of the two most important risk factors, show steepest cognitive decline on non-memory cognitive domains.

Associations between magnetic resonance imaging measures and neuropsychological impairment in early and late onset alzheimer's disease.

AIM: To assess the associations of global atrophy and white matter hyperintensities (WMH) with neuropsychological function in early and late onset Alzheimer's disease (AD). METHODS: We included 107 patients with sporadic AD (21 early onset and 86 late onset) from our memory clinic. Tests for (working) memory, language, executive function, mental speed, and attention were administered. Global atrophy and global and lobar WMH were measured using 1 Tesla MRI. Linear regression analyses with terms for MRI measures, neuropsychological test results, age, gender, education, and the interaction between separate brain measures and age of onset were performed. RESULTS: Global atrophy was associated with more severely impaired global cognition, working memory, mental speed, and executive function (p < 0.05). Significant interactions between global atrophy and age at onset showed that these associations were mostly attributable to patients with early onset AD. By contrast, an association between global atrophy and memory was found, which was specifically attributable to late onset AD patients. No associations between global WMH and cognitive function were found. Subsequently we analyzed regional WMH and found that temporal WMH was associated with impaired memory, and frontal WMH was associated with slower mental speed. CONCLUSION: Cortical atrophy, a key feature of AD, is linked to a wide range of cognitive functions, specifically in early onset AD patients. For WMH, there were no interactions with age at onset, but we found specific associations between temporal WMH and memory and frontal WMH and mental speed.

Cognitive correlates of cerebrospinal fluid biomarkers in frontotemporal dementia.

OBJECTIVE: In this study we investigated the relationships between cerebrospinal fluid (CSF) biomarkers (tau and amyloid-ß1-42 [Aß1-42]) and cognition or behavior in patients with frontotemporal dementia (the behavioral variant, bvFTD). METHODS: We included 58 patients with bvFTD. All patients underwent a neuropsychological assessment and lumbar puncture. Relationships between CSF biomarkers and cognition or behavior were assessed with linear regression analysis. RESULTS: After correction for age, sex, and education, CSF tau levels were found to be negatively related to the Visual Association Test (standardized ß = -0.3, P < .05), whereas CSF Aß1-42 levels were found to be positively related to the Mini-Mental State Examination (ß = 0.3, P < .05), the frontal assessment battery (ß = 0.5, P < .05), and digit span backwards test (ß = 0.3, P = .01). We did not find relations between CSF biomarkers and behavior (measured by the neuropsychiatric inventory). After excluding all patients with a CSF biomarker profile often seen in Alzheimer's disease (high levels of tau and low levels of Aß1-42), we still found relations between CSF Aß1-42 levels and Visual Association Test object naming (ß = 0.4, P < .05), as well as between CSF Aß1-42 levels and the frontal assessment battery (ß = 0.5, P < .05, but there was no relation between CSF tau and cognition. CONCLUSION: Low CSF Aß1-42 levels are associated with worse general cognitive function and worse executive function in patients with bvFTD. Our results provide circumstantial evidence for a pathophysiological role of Aß1-42 in bvFTD.

Episodic memory and the medial temporal lobe: not all it seems. Evidence from the temporal variants of frontotemporal dementia.

BACKGROUND: Disproportionate medial temporal lobe atrophy (MTA) is an early finding in Alzheimer's disease (AD). Episodic memory impairment in AD is associated with the degree of MTA. Episodic memory impairment and MTA are also found in semantic dementia (SD) and in right temporal lobe atrophy (RTLA), the temporal variants of frontotemporal dementia, but their relationship is unclear. OBJECTIVE: To compare episodic memory impairment among patients with these temporal variants of frontotemporal dementia with that of patients with AD with the same degree of MTA. METHODS: Episodic memory was tested with the visual association test, and semantic memory (SM) with animal fluency and the visual association naming test. MTA was measured using a visual rating scale. Each patient with SD or RTLA was matched for MTA with two patients with AD. Comparisons of episodic memory and SM were made for patients with SD versus matched patients with AD; patients with RTLA versus matched patients with AD and for SD, RTLA and all patients with AD. RESULTS: 27 patients with SD and 11 with RTLA were matched with 54 and 22 patients with AD, respectively. Episodic memory was less impaired in patients with SD than in those with AD (8 versus 2; p<0.001) and in patients with RTLA than in those with AD (10 versus 4.5; p=0.009). Semantic memory was more affected in patients with SD than in those with AD, and the Mini Mental State Examination score was higher in patients with RTLA than in those with AD. Comparison of the three diagnostic groups showed that episodic memory was most impaired in AD, whereas SM was most impaired in SD. CONCLUSION: Since episodic memory impairment is more severe in AD than in SD and RTLA, despite a comparable degree of MTA, atrophy of the medial temporal lobe alone cannot account for episodic memory dysfunction.

Microbleeds do not affect rate of cognitive decline in Alzheimer disease.

OBJECTIVE: To investigate the relationship between brain microbleeds (MBs) and the rate of cognitive decline in Alzheimer disease (AD). METHODS: In this cohort study, we studied 221 patients with AD with available baseline MRI scans (1.0 or 1.5 T) and at least 2 Mini-Mental State Examinations (MMSE) scores obtained more than 1 year apart from our memory clinic. Mean ± SD follow-up time was 3 ± 1 years, and patients had a median of 4 MMSE scores (range 2-17). We used linear mixed models with sex and age as covariates to investigate whether MBs influenced the rate of cognitive decline. RESULTS: Mean age was 68 ± 9 years, 109 (49%) patients were female, and the baseline MMSE score was 22 ± 4. There were 39 patients (18%) with MBs (median 2, range 1-27) and 182 without. Linear mixed models showed that overall patients declined 2 MMSE points per year. We found no association of the presence of MBs with baseline MMSE or change in MMSE. Adjustment for atrophy, white matter hyperintensities, lacunes, and vascular risk factors did not change the results nor did stratification for MB location, APOE ε4 carriership, or age at onset (≤65 years vs >65 years). Repeating the analyses with number of MBs as predictor rendered similar results. CONCLUSION: MBs did not influence the rate of cognitive decline in patients with AD. The formerly reported increased risk of mortality in patients with MBs seems not to be attributable to a steeper rate of decline per se but might be due to vascular events, including (hemorrhagic) stroke.

Early onset Alzheimer's disease is associated with a distinct neuropsychological profile.

Alzheimer's disease (AD) in younger patients is associated with a higher prevalence of atypical symptoms. We examined neuropsychological performance according to age-at-onset. We assessed cognition in 172 patients with AD (81 early and 91 late onset) in five cognitive domains (memory, language, visuo-spatial functioning, executive functioning, attention). Dementia severity was assessed using the Mini-Mental State Examination (MMSE) and global cognitive decline using Cambridge Cognitive Examination (CAMCOG). Analyses of variance were performed with age-at-onset as between-subjects factor, and gender and education as covariates. Analysis was repeated after stratification for dementia severity (based on median MMSE). In early onset AD, age (mean ± SD) was 60 ± 4 years; 44 (54%) were female. In late onset AD, age was 72 ± 5 years; 47 (52%) were female. Dementia severity and global cognitive decline did not differ between groups (early onset: MMSE: 20 ± 5, CAMCOG: 69 ± 15, late onset: MMSE: 21 ± 5, CAMCOG: 70 ± 15; p > 0.05). Early onset patients performed worse than late onset patients on visuo-spatial functioning (p < 0.01), executive functioning (p < 0.001), and attention (p < 0.01). Late onset patients performed worse on memory, although not significantly (p = 0.11). Stratification for dementia severity showed that in mildly demented early onset patients, memory function was remarkably preserved compared to late onset patients (p < 0.01). In moderate AD, differences in memory function disappeared, but early onset patients performed worse on visuo-spatial functioning (p < 0.01), executive functioning (p < 0.001), and attention (p < 0.01) than late onset patients. Adjustment for APOE left results unchanged. In conclusion, early onset AD presents with a different cognitive profile and the disease course seems different. Relative sparing of memory function in early stages stresses the need to adequately test other cognitive domains.

Early-versus late-onset Alzheimer's disease: more than age alone.

Alzheimer's disease (AD) is the most common cause of dementia at older age. Although less prevalent before the age of 65 years, it is still the most frequent cause of early-onset dementia followed by frontotemporal dementia. The typical presentation of AD is memory dysfunction, however, presentations with prominent cognitive impairment in other domains besides memory, like prominent apraxia, language problems, or executive dysfunction, may occur and are relatively more common in early-onset AD. In this retrospective descriptive study, we determined the prevalence of non-memory presentations in a large sample of early-onset AD patients compared to late-onset AD. The clinical files of 270 patients with AD starting before the age of 65 years and 90 patients with late-onset AD ( 65 years) were reviewed to assess clinical characteristics. Patients were classified as memory presentation and non-memory presentation according to their clinical presentation. The mean age of the early-onset group was 56 +/- 5 years and 74 +/- 6 years for the late-onset group. A third of the early-onset AD group presented with non-memory symptoms compared to only 6% in the late-onset group (p < 0.001). Within the group with non-memory presentations, apraxia/visuospatial dysfunction was the most prevalent presenting symptom (12%). Patients with early-onset AD often present with a non-memory phenotype, of which apraxia/visuospatial dysfunction is the most common presenting symptom. Atypical presentations of AD should be considered in the clinical differential diagnosis of early-onset dementia.

Early-onset dementia is associated with higher mortality.

BACKGROUND/AIMS: Our objective was to compare the mortality risks of patients with early- and late-onset dementia with non-demented controls of the same age range and to analyse the mortality risks in subtypes of dementia. METHODS: We included 1,203 subjects from our memory clinic. Patients with dementia were subdivided into 2 groups, with early- (<65 years) or late-onset dementia (>or=65 years), and compared with non-demented controls of the same age range. We used Cox proportional hazard models to estimate mortality risks. RESULTS: When compared to non-demented controls of the same age range, the patients with early-onset dementia had a strongly elevated mortality risk [hazard ratio (95% confidence interval) = 43.3 (3.1-600.4)], while those with late-onset dementia had a moderately increased mortality risk compared to older controls [hazard ratio (95% confidence interval) = 3.4 (1.8-6.2)]. An additional analysis showed that, adjusted for age, Alzheimer's disease seemed to have the most benign course, with a fourfold increased mortality risk. Dementia with Lewy bodies and vascular dementia (frequently seen at older age) and frontotemporal lobar degeneration and 'other dementias' (often found at younger age) had a six- to eightfold increased mortality risk. CONCLUSION: Dementia is a risk factor for death. Especially in young patients the impact of dementia on mortality is high.

Cognitive impairment in Alzheimer's disease is modified by APOE genotype.

AIM: We examined whether impairment in specific cognitive domains in Alzheimer's disease (AD) differed according to APOE genotype and age at onset. METHODS: Cognitive functions of 229 consecutive AD patients were assessed using Visual Association Test (VAT), Memory Impairment Screen+ (MIS+), VAT object naming, fluency test and Trail Making Test (TMT). Dementia severity was assessed using MMSE. ANOVAs were performed with APOE genotype and age at onset as independent variables and sex, education and MMSE as covariates. RESULTS: 28% of patients were APOE epsilon4-negative, 58% heterozygous and 14% homozygous. A significant association between APOE genotype and VAT and MIS+ was found when correcting for sex and education. An interaction effect between APOE genotype and age at onset on VAT and VAT object naming was found, with young carriers performing worse than young noncarriers. By contrast, when additionally correcting for MMSE, a significant association between APOE genotype and VAT object naming, TMT-A and TMT-B was found, with noncarriers performing worse than carriers. CONCLUSION: Memory was more impaired among APOE epsilon4 carriers than among noncarriers. By contrast, naming, executive functions and mental speed were more impaired among APOE epsilon4 noncarriers. This suggests that the APOE genotype modifies the clinical phenotype in terms of cognitive impairment in AD.

MRI measures and progression of cognitive decline in nondemented elderly attending a memory clinic.

OBJECTIVE: To investigate whether MRI-based volumes of whole brain, medial temporal lobe and white matter hyperintensities (WMH) predict progression of cognitive decline in a sample of nondemented elderly. METHODS: Thirty-seven nondemented elderly attending a memory clinic and 28 elderly controls participated in this follow-up study. The average follow-up period was 1.8 years. Cognitive function was measured at baseline and follow-up with the Cambridge Cognitive Examination (CAMCOG). Baseline Magnetic Resonance Imaging (MRI) provided quantitative measures of whole brain, medial temporal lobe and WMH. Linear mixed models controlled for age and sex were used to assess the independent associations between MRI measures, baseline cognition, and annual decline in cognition. RESULTS: Medial temporal lobe volume was independently associated with baseline CAMCOG score (p < 0.01), whereas whole brain volume (p < 0.01) and WMH (p < 0.05) were associated with annual decline in CAMCOG score. CONCLUSIONS: These data suggest that regional damage to the medial temporal lobes underlies initial mild cognitive impairment, whereas more global brain changes, such as whole brain atrophy and WMH, contribute to further progression of cognitive decline.