Alzheimer's disease, the commonest cause of dementia, is a growing global health concern with huge implications for individuals and society. In this review, current understanding of the epidemiology, genetics, pathology and pathogenesis of Alzheimer's disease is outlined, before its clinical presentation and current treatment strategies are discussed. Finally, the review discusses how our enhanced understanding of Alzheimer pathogenesis, including the recognition of a protracted preclinical phase, is informing new therapeutic strategies with the aim of moving from treatment to prevention.© 2017 EAN.

We investigated the association of Alzheimer's disease (AD)-related rare variants APP A673T and ABCA7 rs200538373-C with the levels of β-amyloid (Aβ) and parameters of metabolic and cardiovascular health in a population-based cohort of healthy middle-aged and elderly men. Carriers of protective APP A673T variant had, on average, 28% lower levels of Aβ40 and Aβ42 in plasma as compared to the controls and the carriers of ABCA7 rs200538373-C. This is the first report to show decreased Aβ levels in plasma in APP A673T carriers and thus provides evidence that lower Aβ levels throughout life may be protective against AD. Ann Neurol 2017;82:128-132.© 2017 American Neurological Association.

We investigated whether subtypes of Alzheimer's disease (AD), that is, typical, limbic-predominant, hippocampal-sparing, and minimal atrophy AD, had a specific signature of small vessel disease and neurodegeneration. Four hundred twenty-three clinically diagnosed AD patients were included (161 typical, 121 limbic-predominant, 70 hippocampal-sparing, 71 minimal atrophy). One hundred fifty-six fulfilled a biomarkers-based AD diagnosis. White matter hyperintensities and cerebral microbleeds (CMB) had the highest prevalence in limbic-predominant AD, and the lowest prevalence in minimal atrophy AD. CMB existed evenly in lobar and deep brain areas in limbic-predominant, typical, and hippocampal-sparing AD. In minimal atrophy AD, CMB were mainly located in brain lobar areas. Perivascular spaces in the centrum semiovale were more prevalent in typical AD. Small vessel disease contributed to the prediction of Mini-Mental State Examination. Minimal atrophy AD showed highly pathological levels of cerebrospinal fluid Aß, total tau, and phosphorylated tau, in the absence of overt brain atrophy. Cerebral amyloid angiopathy seems to have a stronger contribution to hippocampal-sparing and minimal atrophy AD, whereas hypertensive arteriopathy may have a stronger contribution to typical and limbic-predominant AD.Copyright © 2018 Elsevier Inc. All rights reserved.

TDP-43 immunoreactivity occurs in 19-57 % of Alzheimer's disease (AD) cases. Two patterns of TDP-43 deposition in AD have been described involving hippocampus (limbic) or hippocampus and neocortex (diffuse), although focal amygdala involvement has been observed. In 195 AD cases with TDP-43, we investigated regional TDP-43 immunoreactivity with the aim of developing a TDP-43 in AD staging scheme. TDP-43 immunoreactivity was assessed in amygdala, entorhinal cortex, subiculum, hippocampal dentate gyrus, occipitotemporal, inferior temporal and frontal cortices, and basal ganglia. Clinical, neuroimaging, genetic and pathological characteristics were assessed across stages. Five stages were identified: stage I showed scant-sparse TDP-43 in the amygdala only (17 %); stage II showed moderate-frequent amygdala TDP-43 with spread into entorhinal and subiculum (25 %); stage III showed further spread into dentate gyrus and occipitotemporal cortex (31 %); stage IV showed further spread into inferior temporal cortex (20 %); and stage V showed involvement of frontal cortex and basal ganglia (7 %). Cognition and medial temporal volumes differed across all stages and progression across stages correlated with worsening cognition and medial temporal volume loss. Compared to 147 AD patients without TDP-43, only the Boston Naming Test showed abnormalities in stage I. The findings demonstrate that TDP-43 deposition in AD progresses in a stereotypic manner that can be divided into five distinct topographic stages which are supported by correlations with clinical and neuroimaging features. Given these findings, we recommend sequential regional TDP-43 screening in AD beginning with the amygdala.

The aim of this study was to determine whether the TAR DNA-binding protein of 43 kDa (TDP-43) has any independent effect on the clinical and neuroimaging features typically ascribed to Alzheimer's disease (AD) pathology, and whether TDP-43 pathology could help shed light on the phenomenon of resilient cognition in AD. Three-hundred and forty-two subjects pathologically diagnosed with AD were screened for the presence, burden and distribution of TDP-43. All had been classified as cognitively impaired or normal, prior to death. Atlas-based parcellation and voxel-based morphometry were used to assess regional atrophy on MRI. Regression models controlling for age at death, apolipoprotein ε4 and other AD-related pathologies were utilized to explore associations between TDP-43 and cognition or brain atrophy, stratified by Braak stage. In addition, we determined whether the effects of TDP-43 were mediated by hippocampal sclerosis. One-hundred and ninety-five (57%) cases were TDP-positive. After accounting for age, apolipoprotein ε4 and other pathologies, TDP-43 had a strong effect on cognition, memory loss and medial temporal atrophy in AD. These effects were not mediated by hippocampal sclerosis. TDP-positive subjects were 10× more likely to be cognitively impaired at death compared to TDP-negative subjects. Greater cognitive impairment and medial temporal atrophy were associated with greater TDP-43 burden and more extensive TDP-43 distribution. TDP-43 is an important factor in the manifestation of the clinico-imaging features of AD. TDP-43 also appears to be able to overpower what has been termed resilient brain aging. TDP-43 therefore should be considered a potential therapeutic target for the treatment of AD.

The aim of this study was to determine whether the frequency of TAR DNA-binding protein 43 (TDP-43) deposition in Alzheimer's disease (AD) differs across pathologically defined AD subtypes (hippocampal sparing [HpSp]; typical and limbic) and further examine the relationship between TDP-43, pathological subtype, and clinical features in AD.We identified all cases with pathologically confirmed AD (NIA-Reagan intermediate-high probability, Braak stage IV-VI) independent of cognitive status (n = 188). Neurofibrillary tangle counts were performed using thioflavin-S microscopy in hippocampus and three neocortical regions, and all cases were subtyped: HpSp AD pathology (n = 19); typical AD pathology (n = 136); and limbic AD pathology (n = 33). TDP-43 immunoreactivity was performed in multiple brain regions to assess for the presence of TDP-43 and TDP-43 stage. All cases were clinically subclassified at presentation as amnestic AD dementia versus atypical AD dementia. Statistical analysis was performed using linear and penalized logistic regression to assess associations with pathological subtype, and the effects of TDP-43, accounting for possible interactions between pathological subtype and TDP-43.TDP-43 deposition was frequent in typical (59%) and limbic AD pathologies (67%), but not HpSp AD pathology (21%; p = 0.003). The observed associations of TDP-43 with greater memory loss, naming and functional decline, and smaller hippocampal volumes, closest to death, did not differ across AD pathological subtype. Clinical presentation was associated with pathological subtype (p = 0.01), but not TDP-43 (p = 0.69).Although the frequency of TDP-43 deposition in AD varies by pathological subtype, the observed effects of TDP-43 on clinical/magnetic resonance imaging features are consistent across pathological subtypes. Clinical presentation in AD is driven by pathological subtype, not by TDP-43.© 2015 American Neurological Association.