Defining "prodromal" Alzheimer's disease, frontotemporal dementia, and Lewy body dementia: are we there yet?

Postmortem Brain Imaging in Alzheimer's Disease and Related Dementias: The South Texas Alzheimer's Disease Research Center Repository

BACKGROUND

Neuroimaging bears the promise of providing new biomarkers that could refine the diagnosis of dementia. Still, obtaining the pathology data required to validate the relationship between neuroimaging markers and neurological changes is challenging. Existing data repositories are focused on a single pathology, are too small, or do not precisely match neuroimaging and pathology findings.

OBJECTIVE

The new data repository introduced in this work, the South Texas Alzheimer's Disease research center repository, was designed to address these limitations. Our repository covers a broad diversity of dementias, spans a wide age range, and was specifically designed to draw exact correspondences between neuroimaging and pathology data.

METHODS

Using four different MRI sequences, we are reaching a sample size that allows for validating multimodal neuroimaging biomarkers and studying comorbid conditions. Our imaging protocol was designed to capture markers of cerebrovascular disease and related lesions. Quantification of these lesions is currently underway with MRI-guided histopathological examination.

RESULTS

A total of 139 postmortem brains (70 females) with mean age of 77.9 years were collected, with 71 brains fully analyzed. Of these, only 3% showed evidence of AD-only pathology and 76% had high prevalence of multiple pathologies contributing to clinical diagnosis.

CONCLUSION

This repository has a significant (and increasing) sample size consisting of a wide range of neurodegenerative disorders and employs advanced imaging protocols and MRI-guided histopathological analysis to help disentangle the effects of comorbid disorders to refine diagnosis, prognosis and better understand neurodegenerative disorders.

Signal and Noise: Proton Pump Inhibitors and the Risk of Dementia?

The association between proton pump inhibitor (PPI) use and dementia remains controversial. This cohort study re-examines this issue, addressing shortcomings identified in previous publications using a population-based and a high-dimension propensity-score matched cohort to follow patients for up to 22 years. Cox regression models using baseline characteristics, a lag period, and time-varying variables were used to examine the risk of dementia by cumulative PPI exposure. High-dose PPI users (> 180 days of use) had significantly higher risk of dementia in crude Cox models. After adjustment for medical diagnoses and prescription drug use, these associations disappeared. Among high-dose users starting PPI therapy between 46 and 55 years old, the unadjusted hazard ratio (HR) was 1.55 (95% confidence interval (CI) 1.14, 2.10); the adjusted hazard ratio (aHR) was 1.10 (95% CI 0.80, 1.51). For high-dose users starting therapy between 56 and 65 years, HR = 1.22 (95% CI1.03, 1.44); aHR = 0.99 (95% CI 0.83, 1.17). High-dose users between the ages of 66 and 75 years had no association with the risk of dementia. The use of lag models or time-varying parameters similarly found some association with dementia in crude, but not multivariable Cox models. Although high-dose PPI users were more likely to develop dementia, they were more likely to be diagnosed with dementia risk factors, such as diabetes and cardiovascular disease, which are risk factors for dementia. Controlling for these conditions using multivariable models or a propensity-score matched cohort eliminated this association.

Utilisation of the OliveNet™ Library to investigate phenolic compounds using molecular modelling studies in the context of Alzheimer's disease

Alzheimer's disease (AD) is a debilitating neurodegenerative disease that affects over 47 million people worldwide, and is the most common form of dementia. There is a vast body of literature demonstrating that the disease is caused by an accumulation of toxic extracellular amyloid-β (Aβ) peptides and intracellular neurofibrillary tangles that consist of hyperphosphorylated tau. Adherence to the Mediterranean diet has been shown to reduce the incidence of AD and the phenolic compounds in extra virgin olive oil, including oleocanthal, have gained a significant amount of attention. A large number of these ligands have been described in the pre-existing literature and 222 of these compounds have been characterised in the OliveNet™ database. In this study, molecular docking was used to screen the 222 phenolic compounds from the OliveNet™ database and assess their ability to bind to various forms of the Aβ and tau proteins. The phenolic ligands were found to be binding strongly to the hairpin-turn of the Aβ1-40 and Aβ1-42 monomers, and binding sites were also identified in the tau fibril protein structures. Luteolin-4'-O-rutinoside, oleuricine A, isorhoifolin, luteolin-7-O-rutinoside, cyanidin-3-O-rutinoside and luteolin-7,4-O-diglucoside were predicted to be novel lead compounds. Molecular dynamics (MD) simulations performed using well-known olive ligands bound to Aβ1-42 oligomers highlighted that future work may examine potential anti-aggregating properties of novel compounds in the OliveNet™ database. This may lead to the development and evaluation of new compounds that may have efficacy against Alzheimer's disease.

Anxiety and Depression as Risk Factors in Frontotemporal Dementia and Alzheimer's Disease: The HUNT Study

Background

The roles of both anxiety and depression as risk factors for frontotemporal dementia (FTD) and Alzheimer's disease (AD) have not been previously investigated together.

Objective

To study anxiety and depression as independent risk factors for FTD and AD.

Methods

Eighty-four patients with FTD and 556 patients with AD were compared with 117 cognitively healthy (CH), elderly individuals. Both cases and controls were participants in the second Health Study of Nord-Trøndelag (HUNT2) from 1995 to 1997, in which depression and anxiety were assessed with the Hospital Anxiety and Depression Scale (HADS).

Results

Significant associations were found between anxiety and FTD and between depression and AD. A significantly increased risk of developing FTD was observed in patients who had reported anxiety on the HADS (p = 0.017) (odds ratio [OR]: 2.947, 95% confidence interval [CI]: 1.209-7.158) and a significantly increased risk of developing AD was observed in patients who had reported depression on the HADS (p = 0.016) (OR: 4.389, 95% CI: 1.311-14.690).

Conclusion

Our study findings suggest that anxiety and depression may play different roles as risk factors for FTD and AD.

Spousal recollections of early signs of primary progressive aphasia

BACKGROUND

Although primary progressive aphasia (PPA) is characterized by progressive loss of language and communication skills, knowledge about the earliest emerging signs announcing the onset of this condition is limited.

AIMS

To explore spousal recollections regarding the earliest signs of PPA and to compare the nature of the earliest perceived symptoms across the three PPA variants.

METHODS & PROCEDURES

In-depth interviews focusing on the earliest signs of illness onset were conducted with 13 spouses whose partners were diagnosed with PPA. The earliest recollections and observations described by the spouses were analyzed and coded according to the DSM-5 criteria for a mild neurocognitive disorder. These data were then compared across and within each of the three PPA variants.

OUTCOMES & RESULTS

Spousal retrospective accounts indicated the three PPA variants (semantic, logopenic and non-fluent) had a signature profile announcing illness onset. Changes in social cognition presented in all three variants of PPA, but at different points in the illness trajectory. In particular, the findings suggest the possibility that PPA initially presents as subtle changes in social cognition for semantic variant PPA (svPPA) and logopenic variant PPA (IvPPA) rather than overt language impairments as defined in the current diagnostic criteria.

CONCLUSIONS & IMPLICATIONS

Understanding the nature of symptoms perceived in the earliest stages of PPA has potential to inform earlier and accurate diagnosis and interventions to assist those living with the illness.

Adult ADHD: Risk Factor for Dementia or Phenotypic Mimic?

Attention-deficit hyperactivity disorder (ADHD) has historically been considered a disorder of childhood and adolescence. However, it is now recognized that ADHD symptoms persist into adulthood in up to 60% of individuals. Some of the cognitive symptoms that characterize ADHD (inability to provide sustained attention or mental effort, difficulty organizing or multi-tasking, forgetfulness) may closely resemble symptoms of prodromal dementia, also often referred to as mild cognitive impairment (MCI), particularly in patients over age 50. In addition to the overlap in cognitive symptoms, adults with ADHD and those with MCI may also share a number of behavioral and psychiatric symptoms, including sleep disturbances, depression, and anxiety. As a result, both syndromes may be difficult to distinguish clinically in older patients, particularly those who present to memory clinics with subjective cognitive complaints and fear the onset of a neurodegenerative process: is it ADHD, MCI, or both? Currently, it is unclear whether ADHD is associated with incipient dementia or is being misdiagnosed as MCI due to symptom overlap, as there exist data supporting either possibility. Here, we aim to elucidate this issue by outlining three hypothetical ways in which ADHD and MCI might relate to each other, providing an overview of the evidence relevant to each hypothesis, and delineating areas for future research. This is a question of considerable importance, with implications for improved diagnostic specificity of early dementia, improved accuracy of disease prevalence estimates, and better identification of individuals for targeted treatment.

Activity of muscarinic, galanin and cannabinoid receptors in the prodromal and advanced stages in the triple transgenic mice model of Alzheimer's disease

Neurochemical alterations in Alzheimer's disease (AD) include cholinergic neuronal loss in the nucleus basalis of Meynert (nbM) and a decrease in densities of the M2 muscarinic receptor subtype in areas related to learning and memory. Neuromodulators present in the cholinergic pathways, such as neuropeptides and neurolipids, control these cognitive processes and have become targets of research in order to understand and treat the pathophysiological and clinical stages of the disease. This is the case of the endocannabinoid and galaninergic systems, which have been found to be up-regulated in AD, and could therefore have a neuroprotective role. In the present study, the functional coupling of Gi/o protein-coupled receptors to GalR1, and the CB1 receptor subtype for endocannabinoids were analyzed in the 3xTg-AD mice model of AD. In addition, the activity mediated by Gi/o protein-coupled M2/4 muscarinic receptor subtypes was also analyzed in brain areas involved in anxiety and cognition. Thus, male mice were studied at 4 and 15months of age (prodromal and advanced stages, respectively) and compared to age-matched non-transgenic (NTg) mice (adult and old, respectively). In 4-month-old 3xTg-AD mice, the [(35)S]GTPγS binding stimulated by galanin was significantly increased in the hypothalamus, but a decrease of functional M2/4 receptors was observed in the posterior amygdala. The CB1 cannabinoid receptor activity was up-regulated in the anterior thalamus at that age. In 15-month-old 3xTg-AD mice, muscarinic receptor activity was found to be increased in motor cortex, while CB1 activity was decreased in nbM. No changes were found in GalR1-mediated activity at this age. Our results provide further evidence of the relevance of limbic areas in the prodromal stage of AD, the profile of which is characterized by anxiety. The up-regulation of galaninergic and endocannabinoid systems support the hypothesis of their neuroprotective roles, and these are established prior to the onset of clear clinical cognitive symptoms of the disease.

Is the Mediterranean diet a feasible approach to preserving cognitive function and reducing risk of dementia for older adults in Western countries? New insights and future directions

The rise in the ageing population has resulted in increased incident rates of cognitive impairment and dementia. The subsequent financial and societal burden placed on an already strained public health care system is of increasing concern. Evidence from recent studies has revealed modification of lifestyle and dietary behaviours is, at present, the best means of prevention. Some of the most important findings, in relation to the Mediterranean diet (MedDiet) and the contemporary Western diet, and potential molecular mechanisms underlying the effects of these two diets on age-related cognitive function, are discussed in this review. A major aim of this review was to discuss whether or not a MedDiet intervention would be a feasible preventative approach against cognitive decline for older adults living in Western countries. Critical appraisal of the literature does somewhat support this idea. Demonstrated evidence highlights the MedDiet as a potential strategy to reduce cognitive decline in older age, and suggests the Western diet may play a role in the aetiology of cognitive decline. However, strong intrinsic Western socio-cultural values, traditions and norms may impede on the feasibility of this notion.

Plasma amyloid β, depression, and dementia in community-dwelling elderly

Plasma amyloid β (Aβ) levels have been associated with an increased risk of Alzheimer's disease (AD). As depression is common before the onset of AD, a few clinical studies tested the cross-sectional association of Aβ levels with depression in elderly and showed incongruous findings. Hence, we tested the longitudinal association between Aβ levels and depressive symptoms in community-dwelling elderly. The study is embedded in a population-based cohort of 980 participants aged 60 years or older from the Rotterdam Study with Aβ levels. Participants were evaluated for depressive symptoms with the Centre for Epidemiological Studies-Depression scale at baseline and repeatedly over the mean follow-up of 11 years. We first performed cross-sectional analyses. Then, we tested the longitudinal association between Aβ levels and depressive symptoms after excluding participants with dementia during follow-up. In cross-sectional analyses, persons with high Aβ(1-40) levels had more clinically relevant depressive symptoms. However, this association was accounted for by persons with clinically relevant depressive symptoms who developed dementia within the next 11 years. In longitudinal analyses, persons with low levels of Aβ(1-40) and Aβ(1-42) without dementia had a higher risk of clinically relevant depressive symptoms during the follow-up. These findings suggest that the cross-sectional association between high plasma Aβ levels and clinically relevant depressive symptoms in the elderly is due to prodromal dementia. In contrast, the longitudinal association between low plasma Aβ levels and depressive symptoms could not be explained by dementia during follow-up suggesting that Aβ peptides may play a distinct role on depression etiology.

The role of neuropsychology in prodromal dementia

SUMMARY Before dementia becomes manifest, it is preceded by a long period during which neuropathology exists without clinical symptoms, termed the prodromal stage of dementia (ProD). Owing to its relevance for clinical and research aspects, many efforts are being made to define, diagnose and investigate ProD in greater detail. The ProD state has often been studied in Alzheimer’s disease (AD), whereas less is known about the prodromes of the vascular, extrapyramidal and frontotemporal dementias. Since the operational criteria of ProD are unclear, many studies act on the assumption that ProD and mild cognitive impairment are equivalent concepts. However, owing to several methodological problems with the mild cognitive impairment construct, the viewpoint taken here is that ProD can be understood more profoundly in cohorts of normal elderly subjects. This article discusses the neuropsychological findings of longitudinal, population-based studies, which included elderly, normal subjects, who were followed for years, and made case–control comparisons. Neuropsychological findings clearly revealed deficits in cases (subjects who developed dementia later, mostly AD), which were present already at baseline. Cognitive abnormalities were apparent in the domains of episodic memory, but also in tasks tapping executive, psychomotor and visuospatial functions, attention and naming. Although subtle, these impairments were significant at the group level and often demonstrated deterioration to dementia. Early cognitive deficits of the ProD stage therefore represent markers for the identification of incident AD. It is concluded that neuropsychology is a useful method to screen subjects for ProD at an early time point, when individuals are still normally functioning.

Effects of childhood development on late-life mental disorders

PURPOSE OF REVIEW

To explore recent findings bridging childhood development and common late-life mental disorders in the elderly.

RECENT FINDINGS

We addressed aging as a part of the developmental process in central nervous system, typical and atypical neurodevelopment focusing on genetic and environmental risk factors and their interplay and links between psychopathology from childhood to the elderly, unifying theoretical perspectives and preventive intervention strategies.

SUMMARY

Current findings suggest that childhood development is strictly connected to psychiatric phenotypes across the lifespan. Although we are far from a comprehensive understanding of mental health trajectories, some initial findings document both heterotypic and homotypic continuities from childhood to adulthood and from adulthood to the elderly. Our review also highlights the urgent need for investigations on preventive interventions in individuals at risk for mental disorders.

The utility and benefits of clinical neuropsychology in Asia

Neuropsychological evaluation is the clinical practice of identifying and measuring impairments in mental functions in the context of a patient's mental strengths and preserved abilities for the purposes of diagnosis, rehabilitation planning, and long-term care. Best practice approaches to the medical management of neurodegenerative, neurological and psychiatric illness have lead to increasing demand for neuropsychological services. The simultaneous challenges of Asias' increasing adult and rapidly ageing population underscore the need for consideration of the role of neuropsychological services in day-to-day clinical practice. Here, we outline the clinical utility of neuropsychological assessment and indications for its use in general psychiatric practice.