Low Prevalence and Clinical Effect of Vascular Risk Factors in Early-Onset Alzheimer's Disease

Risk Factors for Young-Onset Dementia in the UK Biobank

Importance

There is limited information on modifiable risk factors for young-onset dementia (YOD).

Objective

To examine factors that are associated with the incidence of YOD.

Design, Setting, and Participants

This prospective cohort study used data from the UK Biobank, with baseline assessment between 2006 and 2010 and follow-up until March 31, 2021, for England and Scotland, and February 28, 2018, for Wales. Participants younger than 65 years and without a dementia diagnosis at baseline assessment were included in this study. Participants who were 65 years and older and those with dementia at baseline were excluded. Data were analyzed from May 2022 to April 2023.

Exposures

A total of 39 potential risk factors were identified from systematic reviews of late-onset dementia and YOD risk factors and grouped into domains of sociodemographic factors (education, socioeconomic status, and sex), genetic factors (apolipoprotein E), lifestyle factors (physical activity, alcohol use, alcohol use disorder, smoking, diet, cognitive activity, social isolation, and marriage), environmental factors (nitrogen oxide, particulate matter, pesticide, and diesel), blood marker factors (vitamin D, C-reactive protein, estimated glomerular filtration rate function, and albumin), cardiometabolic factors (stroke, hypertension, diabetes, hypoglycemia, heart disease, atrial fibrillation, and aspirin use), psychiatric factors (depression, anxiety, benzodiazepine use, delirium, and sleep problems), and other factors (traumatic brain injury, rheumatoid arthritis, thyroid dysfunction, hearing impairment, and handgrip strength).

Main Outcome and Measures

Multivariable Cox proportional hazards regression was used to study the association between the risk factors and incidence of YOD. Factors were tested stepwise first within domains and then across domains.

Results

Of 356 052 included participants, 197 036 (55.3%) were women, and the mean (SD) age at baseline was 54.6 (7.0) years. During 2 891 409 person-years of follow-up, 485 incident YOD cases (251 of 485 men [51.8%]) were observed, yielding an incidence rate of 16.8 per 100 000 person-years (95% CI, 15.4-18.3). In the final model, 15 factors were significantly associated with a higher YOD risk, namely lower formal education, lower socioeconomic status, carrying 2 apolipoprotein ε4 allele, no alcohol use, alcohol use disorder, social isolation, vitamin D deficiency, high C-reactive protein levels, lower handgrip strength, hearing impairment, orthostatic hypotension, stroke, diabetes, heart disease, and depression.

Conclusions and Relevance

In this study, several factors, mostly modifiable, were associated with a higher risk of YOD. These modifiable risk factors should be incorporated in future dementia prevention initiatives and raise new therapeutic possibilities for YOD.

Neuropsychological Profiles, Etiologies, and Medical Comorbidities in Early-Onset Dementia and Cognitive Impairment: A Memory Outpatient Clinic Cohort Study

Background

Although early-onset dementia (EOD) is associated with diagnostic challenges that differ from those of related to late-onset dementia, only limited studies have addressed the neuropsychological and health characteristics or specified the diagnoses underlying early-onset cognitive impairment in a real-world clinical setting.

Objective

To investigate the neuropsychological profiles, etiologies, and comorbidities of an unselected cohort of memory clinic patients (≤65 years at symptom onset).

Methods

The patients' (n = 210) diagnoses were determined based on comprehensive diagnostic workup. Medical comorbidities and neuropsychological profiles were compared between clinically relevant patient groups, namely early-onset dementia (n = 55), mild cognitive impairment due to vascular or suspected neurodegenerative (MCI-n, n = 35) or non-neurodegenerative (MCI-o, n = 106) etiologies, and subjective cognitive decline (n = 14).

Results

The most prevalent diagnoses were Alzheimer's disease (AD, 14%) and depression (11%). Multiple prior medical conditions were common (67%); however, EOD patients had fewer other diagnoses (p = 0.008) than MCI-o patients. Compared to other groups, EOD patients had more severe deficits (p < 0.001) on immediate and delayed memory, processing speed, symptom awareness, and global cognition. AD patients had weaker memory retention ability but less behavioral symptoms than frontotemporal dementia (FTD) patients (p≤0.05). Depression was associated with better immediate memory, symptom awareness, and global cognition than AD and FTD (p < 0.05).

Conclusions

EOD is associated with more severe and widespread neuropsychological deficits but fewer prior medical diagnoses than nondegenerative etiologies of cognitive impairment. AD and depression are common etiologies and the neuropsychological profiles are partly overlapping; however, memory, symptom awareness and global cognitive impairment measures may help in the differential diagnosis.

[Features of the clinical and neuroimaging picture in patients with early-onset Alzheimer's disease]

The most common cause of severe cognitive impairment in adults is Alzheimer's disease (AD). Depending on the age of onset, AD is divided into early (<65 years) and late (≥65 years) forms. Early-onset AD (EOAD) is significantly less common than later-onset AD (LOAD) and accounts for only about 5-10% of cases. However, its medical and social significance, as a disease leading to loss of ability to work and legal capacity, as well as premature death in patients aged 40-64 years, is extremely high. Patients with EOAD compared with LOAD have a greater number of atypical clinical variants - 25% and 6-12.5%, respectively, which complicates the differential diagnosis of EOAD with other neurodegenerative diseases. However, the typical classical amnestic variant predominates in both EOAD and LOAD. Also, patients with EOAD have peculiarities according to neuroimaging data: when performing MRI of the brain, patients with EOAD often have more pronounced parietal atrophy and less pronounced hippocampal atrophy compared to patients with LOAD. The article pays attention to the features of the clinical and neuroimaging data in patients with EOAD; a case of a patient with EOAD is presented.

Associations of socioeconomic status and healthy lifestyle with incident early-onset and late-onset dementia: a prospective cohort study

BACKGROUND

Modifiable risk factor estimates are sparse for early-onset dementia incidence. This study aimed to estimate and compare the risk factor profiles of early-onset dementia and late-onset dementia, and to explore the complex relationships between socioeconomic status, lifestyles, and early-onset dementia risk.

METHODS

In this prospective cohort study, we used data from the UK Biobank for analysis of early-onset dementia and late-onset dementia. For early-onset dementia analyses, data were collected on those aged younger than 60 years without prevalent dementia at baseline. For late-onset dementia analyses, data were collected on those aged 65 years or older at the end of follow-up. Participants with missing information on socioeconomic factors were excluded. Two models were used to test associations between early-onset dementia incidence and socioeconomic status. The first model tested associations between socioeconomic status and early-onset and late-onset dementia incidence, adjusting for covariates. Participant socioeconomic status was defined using education level, income, and employment status via latent class analysis. The second model additionally included a healthy lifestyle score, which was constructed using data on smoking, alcohol consumption, physical activity, and the Healthy Diet Index. Incident early-onset dementia was defined as a dementia case diagnosed before 65 years of age. Multivariable-adjusted Cox proportional hazard regression models were used to estimate the hazard ratio (HR) for risk of dementia. We used multivariable-adjusted Cox proportional-hazard regression models to estimate the HR for risk of both early-onset dementia and late-onset dementia.

FINDINGS

Between 2007 and 2010, 257 345 individuals were included in the analysis of early-onset dementia, and 294 133 older individuals were included in the analysis of late-onset dementia. During a mean follow-up of 11·9-12·5 years, 502 early-onset dementia cases and 5768 late-onset dementia cases were documented. Risk factor profiles were typically dissimilar between early-onset dementia and late-onset dementia. For instance, the age and sex adjusted HR for low socioeconomic status (vs high) was 4·40 (95% CI 3·43-5·65) for early-onset dementia and 1·90 (1·74-2·07) for late-onset dementia, yielding a ratio of HRs of 2·32 (1·78-3·02). After adjusting for various risk factors, participants with low socioeconomic status (vs high) had increased risk for early-onset dementia (3·38, 2·61-4·37), and overall lifestyle mediated 3·2% (1·8-5·7) of the association. Individuals with both low socioeconomic status and unhealthy lifestyles had a higher risk of early-onset dementia (5·40, 3·66-7·97). No significant interaction was observed between lifestyle and socioeconomic status. The association between socioeconomic status and early-onset dementia seemed to be more pronounced in individuals with type 2 diabetes (HR 11·21, 95% CI 2·70-46·57).

INTERPRETATION

Early-onset dementia and late-onset dementia might have different risk factor profiles; although risk factors were similar, the magnitude of associations between risk factors and dementia incidence was greater for early-onset dementia. Only a small proportion of the socioeconomic inequity in dementia risk was mediated by healthy lifestyles, which indicates that measures other than healthy lifestyle promotion to improve social determinants of health are warranted.

FUNDING

The National Key Research and Development Program of China, the National Natural Science Foundation of China, the Hubei Province Science Fund for Distinguished Young Scholars, and the Fundamental Research Funds for the Central Universities.

Young-Onset Dementia and Neurodegenerative Disorders of the Young With an Emphasis on Clinical Manifestations

Young-onset dementia (YOD) refers to a neurological ailment primarily affecting people below 65 years of age in roughly about 8% of cases found through various researches. The high rate of prevalence of secondary dementias among older patients proves that younger people show a better prognosis of the conditions causing dementia than older people. However, effective interventions have to be usually provided early in the course of cognitive decline to help facilitate cognitive improvement. The risk of development of prodromal dementia is high if there is a development of psychoses in middle-aged or older people. When there is a development of psychoses in middle to late life, the likelihood of this indicates prodromal dementia is high. The clinical presentation is quite variable and often subtle in frontotemporal dementia (FTD) but may be dominated by personality change, behavioral disturbances, motivation, or the loss of empathy. There is great heterogeneity in the probable causes of dementia in young age as compared to dementia in old age, and some observed differences also exist in the course and characteristics of the disease. These causes may range from the most probable cause such as Alzheimer's disease (AD) to causes with low probability, such as metabolic disorders and prion diseases. The symptoms of young-onset dementia include a gradual development of personality and behavioral changes over a period of years. However, in the initial stages of young-onset dementia, this change can be attributed to various issues, such as depression, marital problems, and menopause. Other neurodegenerative diseases such as Huntington's disease show presentations such as changes in personality, chorea, and depression that can be observed in patients in their early adulthood. A few other neurodegenerative disorders are myoclonic epilepsy with ragged red fibers (MERRF) and mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) with presentations such as characterized muscle weakness, poor growth, problems with vision and hearing, and the involvement of the multi-organ system, including the central nervous system to name a few. There is also the prevalence of juvenile parkinsonism in the community, which represents a group of clinicopathological entities present before the age of 21. Young-onset Parkinson's disease (PD) (YOPD) appears to have the same pathological presentation as late-onset Parkinson's disease (LOPD). Recent researches have proved that "gene therapy" can be useful in the treatment and in preventing the progression of symptoms in cases of neurodegenerative diseases.

Regional associations of white matter hyperintensities and early cortical amyloid pathology

White matter hyperintensities (WMHs) have a heterogeneous aetiology, associated with both vascular risk factors and amyloidosis due to Alzheimer's disease. While spatial distribution of both amyloid and WM lesions carry important information for the underlying pathogenic mechanisms, the regional relationship between these two pathologies and their joint contribution to early cognitive deterioration remains largely unexplored. We included 662 non-demented participants from three Amyloid Imaging to Prevent Alzheimer's disease (AMYPAD)-affiliated cohorts: EPAD-LCS (N = 176), ALFA+ (N = 310), and EMIF-AD PreclinAD Twin60++ (N = 176). Using PET imaging, cortical amyloid burden was assessed regionally within early accumulating regions (medial orbitofrontal, precuneus, and cuneus) and globally, using the Centiloid method. Regional WMH volume was computed using Bayesian Model Selection. Global associations between WMH, amyloid, and cardiovascular risk scores (Framingham and CAIDE) were assessed using linear models. Partial least square (PLS) regression was used to identify regional associations. Models were adjusted for age, sex, and APOE-e4 status. Individual PLS scores were then related to cognitive performance in 4 domains (attention, memory, executive functioning, and language). While no significant global association was found, the PLS model yielded two components of interest. In the first PLS component, a fronto-parietal WMH pattern was associated with medial orbitofrontal-precuneal amyloid, vascular risk, and age. Component 2 showed a posterior WMH pattern associated with precuneus-cuneus amyloid, less related to age or vascular risk. Component 1 was associated with lower performance in all cognitive domains, while component 2 only with worse memory. In a large pre-dementia population, we observed two distinct patterns of regional associations between WMH and amyloid burden, and demonstrated their joint influence on cognitive processes. These two components could reflect the existence of vascular-dependent and -independent manifestations of WMH-amyloid regional association that might be related to distinct primary pathophysiology.

Environmental and lifestyle risk factors for early-onset dementia: a systematic review

BACKGROUND AND AIM

The term early-onset dementia (EOD) encompasses several forms of neurodegenerative diseases characterized by symptom onset before 65 years and leading to severe impact on subjects already in working activities, as well as on their family and caregivers. Despite the increasing incidence, the etiology is still unknown, with possible association of environmental factors, although the evidence is still scarce. In this review, we aimed to assess how several environmental and lifestyle factors may be associated with the onset of this disease.

METHODS

We conducted a literature search in PubMed and EMBASE databases up to May 6, 2022, to retrieve epidemiological studies evaluating the effect of environmental and lifestyle factors on EOD risk.

RESULTS

We eventually included 22 studies, ten with cohort and twelve with case-control design. Traumatic injury, especially on the head/brain, some cardiovascular diseases such as atrial fibrillation and stroke, metabolic diseases including diabetes and hypercholesterolemia, and alcohol consumption have been identified as potential risk factors for EOD. Conversely, playing leisure activities including sports (without trauma), higher educational attainment and higher adherence to Mediterranean DASH-Intervention for Neurodegenerative Delay (MIND) diet appeared to be protective for EOD.

CONCLUSIONS

The literature on environmental risk factors for EOD has been considerably growing in recent years. Overall, it supports an association between some environmental and lifestyle factors with disease risk. However, additional high-quality research is required to confirm these relations and its causal nature (www.actabiomedica.it).

A multimodal, longitudinal study of cognitive heterogeneity in early-onset Alzheimer's disease

BACKGROUND AND PURPOSE

Alzheimer's disease (AD) is a heterogeneous pathology. Young patients with AD are particularly likely to have an atypical presentation. The objectives of the present cluster analysis were to determine whether patients with early-onset AD (EOAD) had several distinct cognitive profiles and to compare the resulting clusters with regard to clinical, neuroimaging, and laboratory characteristics.

METHODS

We collected cognitive, behavioural, functional, neuroimaging, and laboratory data on 72 patients meeting the criteria for probable mild EOAD. The patients were first classified into clinical phenotype groups by a multidisciplinary board of clinicians. The patients' cognitive and functional decline was monitored for 24 months. A k-means clustering analysis was then used to determine clusters on the basis of the patients' neuropsychological test results.

RESULTS

Two distinct clusters were identified: the patients in the first cluster (C1, n = 38) had a predominant memory impairment, whereas patients in the second (C2, n = 34) did not. Dyslipidaemia and the presence of ɛ4 apolipoprotein E allele were more frequent in C1, whereas the cognitive and functional decline was faster in the patients in C2. Moreover, posterior brain abnormalities were more severe in patients in C2 than in patients in C1.

CONCLUSIONS

By applying a k-means clustering analysis, we identified two clusters of patients in an EOAD cohort. The clusters differed with regard to certain clinical, imaging, and laboratory characteristics. This clustering procedure might be of value for managing patients with EOAD in general and for identifying those at risk of more rapid decline in particular.

Prevalence and incidence of young onset dementia and associations with comorbidities: A study of data from the French national health data system

BACKGROUND

Dementia onset in those aged <65 years (young onset dementia, YOD) has dramatic individual and societal consequences. In the context of population aging, data on YOD are of major importance to anticipate needs for planning and allocation of health and social resources. Few studies have provided precise frequency estimates of YOD. The aim of this study is to provide YOD prevalence and incidence estimates in France and to study the contribution of comorbidities to YOD incidence.

METHODS AND FINDINGS

Using data from the French national health data system (Système National des Données de Santé, SNDS) for 76% of the French population aged 40 to 64 years in 2016 (n = 16,665,795), we identified all persons with dementia based on at least 1 of 3 criteria: anti-Alzheimer drugs claims, hospitalization with the International Classification of Diseases-10th Revision (ICD-10) dementia codes (F00 to F03, G30, G31.0, G31.1, or F05.1), or registration for free healthcare for dementia. We estimated prevalence rate (PR) and incidence rate (IR) and estimated the association of comorbidities with incident YOD. Sex differences were investigated. We identified 18,466 (PRstandardized = 109.7/100,000) and 4,074 incident (IRstandardized = 24.4/100,000 person-years) persons with prevalent and incident YOD, respectively. PR and IR sharply increased with age. Age-adjusted PR and IR were 33% (95% confidence interval (CI) = 29 to 37) and 39% (95% CI = 31 to 48) higher in men than women (p < 0.001 both for PR and IR). Cardio- and cerebrovascular, neurological, psychiatric diseases, and traumatic brain injury prevalence were associated with incident YOD (age- and sex-adjusted p-values <0.001 for all comorbidities examined, except p = 0.109 for antihypertensive drug therapy). Adjustment for all comorbidities explained more than 55% of the sex difference in YOD incidence. The lack of information regarding dementia subtypes is the main limitation of this study.

CONCLUSIONS

We estimated that there were approximately 24,000 and approximately 5,300 persons with prevalent and incident YOD, respectively, in France in 2016. The higher YOD frequency in men may be partly explained by higher prevalence of cardiovascular and neurovascular diseases, substance abuse disorders, and traumatic brain injury and warrants further investigation.

The Clinical Spectrum of Young Onset Dementia Points to Its Stochastic Origins

BACKGROUND

Dementia is a major global health problem and the search for improved therapies is ongoing. The study of young onset dementia (YOD)-with onset prior to 65 years-represents a challenge owing to the variety of clinical presentations, pathology, and gene mutations. The advantage of the investigation of YOD is the lack of comorbidities that complicate the clinical picture in older adults. Here we explore the origins of YOD.

OBJECTIVE

To define the clinical diversity of YOD in terms of its demography, range of presentations, neurological examination findings, comorbidities, medical history, cognitive findings, imaging abnormalities both structural and functional, electroencephagraphic (EEG) data, neuropathology, and genetics.

METHODS

A prospective 20-year study of 240 community-based patients referred to specialty neurology clinics established to elucidate the nature of YOD.

RESULTS

Alzheimer's disease (AD; n = 139) and behavioral variant frontotemporal (bvFTD; n = 58) were the most common causes with a mean age of onset of 56.5 years for AD (±1 SD 5.45) and 57.1 years for bvFTD (±1 SD 5.66). Neuropathology showed a variety of diagnoses from multiple sclerosis, Lewy body disease, FTD-MND, TDP-43 proteinopathy, adult-onset leukoencephalopathy with axonal steroids and pigmented glia, corticobasal degeneration, unexplained small vessel disease, and autoimmune T-cell encephalitis. Non-amnestic forms of AD and alternative forms of FTD were discovered. Mutations were only found in 11 subjects (11/240 = 4.6%). APOE genotyping was not divergent between the two populations.

CONCLUSION

There are multiple kinds of YOD, and most are sporadic. These observations point to their stochastic origins.

β-Amyloid Orchestrates Factor XII and Platelet Activation Leading to Endothelial Dysfunction and Abnormal Fibrinolysis in Alzheimer Disease

Alzheimer disease (AD) is the most common form of dementia in humans. However, to date, the cause of sporadic AD (SAD), which is the most frequent form, is still unknown. Although it has not been possible to determine the origin of this disease, the amyloid hypothesis is one of the most accepted to explain the etiology of AD. This hypothesis proposes that the pathogenesis of AD is derived from the toxic effect produced by the amyloid-β (Aβ) peptide in the brain parenchyma, but it does not make clear how Aβ is capable of producing such damage. Furthermore, it has been observed that SAD is accompanied by disruptions in the vascular system, such as damage to the blood-brain barrier. This facilitates the transfer of some systemic proteins, such as fibrinogen, to the brain parenchyma, where Aβ is abundant. Therefore, this Aβ interacts with fibrinogen, which favors the formation of clots resistant to fibrinolysis, inducing a risk of thrombosis and neuroinflammation. Notably, Aβ is not only of neuronal origin; platelets also contribute to high Aβ production in the circulation. The Aβ present in circulation favors the activation of coagulation factor XII, which leads to the generation of thrombin and bradykinin. In addition to Aβ-induced platelet activation, all these events favor the development of inflammatory processes that cause damage to the brain vasculature. This damage represents the beginning of the toxic effects of Aβ, which supports the amyloid hypothesis. This review addresses the relationship between alterations in the vascular and hemostatic systems caused by Aβ and how both alterations contribute to the progression of SAD.

Nutritional Assessment in Patients with Early-Onset Autosomal Dominant Alzheimer's Disease Due to PSEN1- E280A Genetic Variant: A Cross-Sectional Study

Background

Weight loss and malnutrition are frequent findings in late-onset and sporadic presentations of Alzheimer's Disease (AD). However, less is known about nutritional status in Early-Onset Autosomal Dominant AD (EO-ADAD).

Objective

To analyze the association between nutritional status and other clinical and sociodemographic characteristics in individuals with a genetic form of EO-ADAD.

Design settings and participants

Cross-sectional study with 75 non-institutionalized participants from a cohort of Autosomal Dominant AD (13 with mild cognitive impairment and 61 with dementia, ages from 38 to 67 years) underwent a structured clinical assessment with emphasis on nutritional status.

Measurements

Primary outcome was nutritional status and it was measured using the Mini Nutritional Assessment (MNA). Patients were categorized according to MNA total score, as undernourished (MNA ≤23.5) and well-nourished (MNA ≥ 24). Sociodemographic and clinical variables identified as potential predictors or confounders of nutritional status were also collected.

Results

Undernourishment by MNA was present in 57.3% of the sample. Forty-two percent of participants had abnormal BMI values considered lower than 18.5 or higher than 24.9 kg/m2. Total BMI values were similar in well and undernourished patients (median 24.2 IQR 3.59 and median 23.9 IQR 4.42, respectively, p=0.476). When comparing well and undernourished groups, we found statistically significant differences for variables: severity of dementia (p=0.034), frailty (p=0.001), multimorbidity (p=0.035) and, polymedication (p=0.045). Neither adjusted logistic regression nor the Poisson regression showed that any clinical or sociodemographic variables explained undernourishment.

Conclusions

Undernourishment was a frequent finding in our sample of EO-ADAD, especially in later stages of the disease. Patients with polymedication, multimorbidity, frailty and severe dementia show differences in their nutritional status with a tendency to be more frequently undernourished. Further studies with larger sample sizes are needed to establish this association.

Early-onset Alzheimer Disease and Its Variants

PURPOSE OF REVIEW

Early-onset Alzheimer disease (AD) is defined as having an age of onset younger than 65 years. While early-onset AD is often overshadowed by the more common late-onset AD, recognition of the differences between early- and late-onset AD is important for clinicians.

RECENT FINDINGS

Early-onset AD comprises about 5% to 6% of cases of AD and includes a substantial percentage of phenotypic variants that differ from the usual amnestic presentation of typical AD. Characteristics of early-onset AD in comparison to late-onset AD include a larger genetic predisposition (familial mutations and summed polygenic risk), more aggressive course, more frequent delay in diagnosis, higher prevalence of traumatic brain injury, less memory impairment and greater involvement of other cognitive domains on presentation, and greater psychosocial difficulties. Neuroimaging features of early-onset AD in comparison to late-onset AD include greater frequency of hippocampal sparing and posterior neocortical atrophy, increased tau burden, and greater connectomic changes affecting frontoparietal networks rather than the default mode network.

SUMMARY

Early-onset AD differs substantially from late-onset AD, with different phenotypic presentations, greater genetic predisposition, and differences in neuropathologic burden and topography. Early-onset AD more often presents with nonamnestic phenotypic variants that spare the hippocampi and with greater tau burden in posterior neocortices. The early-onset AD phenotypic variants involve different neural networks than typical AD. The management of early-onset AD is similar to that of late-onset AD but with special emphasis on targeting specific cognitive areas and more age-appropriate psychosocial support and education.

Non-Genetic Risk Factors for Degenerative and Vascular Young Onset Dementia: Results from the INSPIRED and KGOW Studies

BACKGROUND

Several brain reserve, vascular risk, and other modifiable factors have been associated with late-onset dementia, but their association with young onset dementia (YOD) has not been adequately explored.

OBJECTIVE

To examine the association of cognitive reserve enhancing factors, cardiovascular risk factors (including smoking), depression, alcohol use, and traumatic brain injury (TBI) with non-autosomal dominant degenerative and/or vascular YOD.

METHODS

Data for this matched case-control study were taken from two larger studies conducted in NSW, Australia. One comprised all people with YOD within a geographical region, while the other exclusively included Aboriginal and Torres Strait Islander participants. Dementia diagnosis was confirmed by clinical consensus, and risk exposure was retrospectively self- and/or informant-reported.

RESULTS

Participants were 96 people with YOD (58.4% with probable Alzheimer's disease) and 175 age-group, sex, and sample matched control participants. Poor educational attainment, low participation in cognitive leisure activity, stroke, transient ischemic attack, and self-reported very heavy alcohol use were related to the risk of primary degenerative and/or vascular YOD. The effect of hypertension and depression varied depending on when they occurred relative to dementia onset. Current smoking was significantly associated with risk in univariate analyses but did not retain significance in multivariate modelling. There was no association with hypercholesterolemia, diabetes, or TBI of any kind. Some compensation for low educational attainment was possible via a complex occupation later in life.

CONCLUSION

Non-genetic factors have a role in YOD, though the relative importance of each factor may be different to late onset dementia. The timing and severity of exposure, as well as the potential for compensation with later protective exposures, are important considerations for potential prevention strategies.

Modifiable risk factors for young onset dementia

PURPOSE OF REVIEW

Although young onset dementia (YOD) causes high levels of burden and distress, factors that contribute to its onset are not well understood. Identifying relevant modifiable risk and protective factors for YOD can inform efforts to prevent or delay onset of symptoms to later in life.

RECENT FINDINGS

Studies of modifiable factors for YOD have increased in frequency in recent years. Poor educational attainment and low socioeconomic status, a history of heavy alcohol use, and poor cardiovascular health may be key targets for YOD prevention or delay. Traumatic brain injury has attracted significant attention but evidence of its importance is limited except in cases occurring secondarily to the injury.

SUMMARY

A growing body of evidence suggests that modifiable risk factors have a role in modulating the age of dementia onset. Clinicians should be aware that many people with YOD will present with complex histories of multifactorial (including modifiable and nonmodifiable) risk exposure. Exploring trajectories of risk and gene-environment interactions is an important future research direction and will inform targeted prevention efforts.

The relationship between CSF biomarkers and cerebral metabolism in early-onset Alzheimer's disease

PURPOSE

One can reasonably suppose that cerebrospinal spinal fluid (CSF) biomarkers can identify distinct subgroups of Alzheimer's disease (AD) patients. In order to better understand differences in CSF biomarker patterns, we used FDG PET to assess cerebral metabolism in CSF-based subgroups of AD patients.

METHODS

Eighty-five patients fulfilling the criteria for probable early-onset AD (EOAD) underwent lumbar puncture, brain ¹⁸F-FDG PET and MRI. A cluster analysis was performed, with the CSF biomarkers for AD as variables. Vertex-wise, partial-volume-corrected metabolic maps were computed for the patients and compared between the clusters of patients. Linear correlations between each CSF biomarker and the metabolic maps were assessed.

RESULTS

Three clusters emerged. The "Aβ42" cluster contained 32 patients with low levels of Aβ42, while tau and p-tau remained within the normal range. The "Aβ42 + tau" cluster contained 41 patients with low levels of Aβ42 and high levels of tau and p-tau. Lastly, the "tau" cluster contained 12 patients with very high levels of tau and p-tau and low-normal levels of Aβ42. There were no inter-cluster differences in age, sex ratio, educational level, APOE genotype, disease duration or disease severity. The "Aβ42 + tau" and "tau" clusters displayed more marked frontal hypometabolism than the "Aβ42" cluster did, and frontal metabolism was significantly negatively correlated with the CSF tau level. The "Aβ42" and "Aβ42 + tau" clusters displayed more marked hypometabolism in the left occipitotemporal region than the "tau" cluster did, and metabolism in this region was significantly and positively correlated with the CSF Aβ42 level.

CONCLUSION

The CSF biomarkers can be used to identify metabolically distinct subgroups of patients with EOAD. Future research should seek to establish whether these biochemical differences have clinical consequences.

Pleiotropy and promiscuity in pharmacogenomics for the treatment of Alzheimer's disease and related risk factors

Patients with Alzheimer's disease are current consumers of polypharmacy with a high risk for drug–drug interactions. Antidementia drugs and other pharmacological treatments for vascular risk factors associated with dementia exert pleiotropic effects which are promiscuously regulated by different gene products. The aim of this review is to highlight the influence of genes involved in pharmacogenetics (i.e., pathogenic, mechanistic, metabolic, transporter and pleiotropic genes) as major determinants of response to treatment in Alzheimer's disease. Patients harboring poor or ultrarapid geno-phenotypes display more irregular profiles in drug efficacy and safety than extensive or intermediate metabolizers. Polymorphic variants of genes associated with lipid metabolism influence the therapeutic response to hypolipemic agents. Understanding these effects is very useful for optimizing polytherapy in dementia.

Pharmacogenetics of Vascular Risk Factors in Alzheimer's Disease

Alzheimer’s disease (AD) is a polygenic/complex disorder in which genomic, epigenomic, cerebrovascular, metabolic, and environmental factors converge to define a progressive neurodegenerative phenotype. Pharmacogenetics is a major determinant of therapeutic outcome in AD. Different categories of genes are potentially involved in the pharmacogenetic network responsible for drug efficacy and safety, including pathogenic, mechanistic, metabolic, transporter, and pleiotropic genes. However, most drugs exert pleiotropic effects that are promiscuously regulated for different gene products. Only 20% of the Caucasian population are extensive metabolizers for tetragenic haplotypes integrating CYP2D6-CYP2C19-CYP2C9-CYP3A4/5 variants. Patients harboring CYP-related poor (PM) and/or ultra-rapid (UM) geno-phenotypes display more irregular profiles in drug metabolism than extensive (EM) or intermediate (IM) metabolizers. Among 111 pentagenic (APOE-APOB-APOC3-CETP-LPL) haplotypes associated with lipid metabolism, carriers of the H26 haplotype (23-TT-CG-AG-CC) exhibit the lowest cholesterol levels, and patients with the H104 haplotype (44-CC-CC-AA-CC) are severely hypercholesterolemic. Furthermore, APOE, NOS3, ACE, AGT, and CYP variants influence the therapeutic response to hypotensive drugs in AD patients with hypertension. Consequently, the implementation of pharmacogenetic procedures may optimize therapeutics in AD patients under polypharmacy regimes for the treatment of concomitant vascular disorders.