ABSTRACT
Frailty is a complex, age-related clinical condition that involves multiple contributing factors and raises the risk of adverse outcomes in older people. Given global population ageing trends, the growing prevalence and incidence of frailty pose significant challenges to health and social care systems in both high-income and lower-income countries. In this review, we highlight the disproportionate representation of research on frailty screening and management from high-income countries, despite how lower-income countries are projected to have a larger share of older people aged ≥60. However, more frailty research has been emerging from lower-income countries in recent years, paving the way for more context-specific guidelines and studies that validate frailty assessment tools and evaluate frailty interventions in the population. We then present further considerations for contextualising frailty in research and practice in lower-income countries. First, the heterogeneous manifestations of frailty call for research that reflects different geographies, populations, health systems, community settings and policy priorities; this can be driven by supportive collaborative systems between high-income and lower-income countries. Second, the global narrative around frailty and ageing needs re-evaluation, given the negative connotations linked with frailty and the introduction of intrinsic capacity by the World Health Organization as a measure of functional reserves throughout the life course. Finally, the social determinants of health as possible risk factors for frailty in lower-income countries and global majority populations, and potential socioeconomic threats of frailty to national economies warrant proactive frailty screening in these populations.
Subject(s)
Frailty , Global Health , Humans , Aged , Frail Elderly , Geriatric Assessment , Developing Countries , Aging , Aged, 80 and over , Social Determinants of HealthABSTRACT
BACKGROUND: Technology-enabled inpatient-level care at home services, such as virtual wards and hospital at home, are being rapidly implemented. This is the first systematic review to link the components of these service delivery innovations to evidence of effectiveness to explore implications for practice and research. METHODS: For this review (registered here https://osf.io/je39y ), we searched Cochrane-recommended multiple databases up to 30 November 2022 and additional resources for randomised and non-randomised studies that compared technology-enabled inpatient-level care at home with hospital-based inpatient care. We classified interventions into care model groups using three key components: clinical activities, workforce, and technology. We synthesised evidence by these groups quantitatively or narratively for mortality, hospital readmissions, cost-effectiveness and length of stay. RESULTS: We include 69 studies: 38 randomised studies (6413 participants; largely judged as low or unclear risk of bias) and 31 non-randomised studies (31,950 participants; largely judged at serious or critical risk of bias). The 69 studies described 63 interventions which formed eight model groups. Most models, regardless of using low- or high-intensity technology, may have similar or reduced hospital readmission risk compared with hospital-based inpatient care (low-certainty evidence from randomised trials). For mortality, most models had uncertain or unavailable evidence. Two exceptions were low technology-enabled models that involve hospital- and community-based professionals, they may have similar mortality risk compared with hospital-based inpatient care (low- or moderate-certainty evidence from randomised trials). Cost-effectiveness evidence is unavailable for high technology-enabled models, but sparse evidence suggests the low technology-enabled multidisciplinary care delivered by hospital-based teams appears more cost-effective than hospital-based care for those with chronic obstructive pulmonary disease (COPD) exacerbations. CONCLUSIONS: Low-certainty evidence suggests that none of technology-enabled care at home models we explored put people at higher risk of readmission compared with hospital-based care. Where limited evidence on mortality is available, there appears to be no additional risk of mortality due to use of technology-enabled at home models. It is unclear whether inpatient-level care at home using higher levels of technology confers additional benefits. Further research should focus on clearly defined interventions in high-priority populations and include comparative cost-effectiveness evaluation. TRIAL REGISTRATION: https://osf.io/je39y .
Subject(s)
Home Care Services , Humans , Inpatients , Cost-Benefit Analysis , Home Care Services, Hospital-Based/economicsABSTRACT
Delirium is common in hospitalised patients, and there is currently no specific treatment. Identifying and treating underlying somatic causes of delirium is the first priority once delirium is diagnosed. Several international guidelines provide clinicians with an evidence-based approach to screening, diagnosis and symptomatic treatment. However, current guidelines do not offer a structured approach to identification of underlying causes. A panel of 37 internationally recognised delirium experts from diverse medical backgrounds worked together in a modified Delphi approach via an online platform. Consensus was reached after five voting rounds. The final product of this project is a set of three delirium management algorithms (the Delirium Delphi Algorithms), one for ward patients, one for patients after cardiac surgery and one for patients in the intensive care unit.
ABSTRACT
There are national and global moves to improve effective digital data design and application in healthcare. This New Horizons commentary describes the role of digital data in healthcare of the ageing population. We outline how health and social care professionals can engage in the proactive design of digital systems that appropriately serve people as they age, carers and the workforce that supports them. KEY POINTS: Healthcare improvements have resulted in increased population longevity and hence multimorbidity. Shared care records to improve communication and information continuity across care settings hold potential for older people. Data structure and coding are key considerations. A workforce with expertise in caring for older people with relevant knowledge and skills in digital healthcare is important.
Subject(s)
Aging , Delivery of Health Care , Humans , Aged , Caregivers , Communication , LongevityABSTRACT
BACKGROUND: Virtual wards are being rapidly developed within the National Health Service in the UK, and frailty is one of the first clinical pathways. Virtual wards for older people and existing hospital at home services are closely related. METHODS: In March 2022, we searched Medline, CINAHL, the Cochrane Database of Systematic Reviews and medRxiv for evidence syntheses which addressed clinical-effectiveness, cost-effectiveness, barriers and facilitators, or staff, patient or carer experience for virtual wards, hospital at home or remote monitoring alternatives to inpatient care. RESULTS: We included 28 evidence syntheses mostly relating to hospital at home. There is low to moderate certainty evidence that clinical outcomes including mortality (example pooled RR 0.77, 95% CI 0.60-0.99) were probably equivalent or better for hospital at home. Subsequent residential care admissions are probably reduced (example pooled RR 0.35, 95% CI 0.22-0.57). Cost-effectiveness evidence demonstrated methodological issues which mean the results are uncertain. Evidence is lacking on cost implications for patients and carers. Barriers and facilitators operate at multiple levels (organisational, clinical and patient). Patient satisfaction may be improved by hospital at home relative to inpatient care. Evidence for carer experience is limited. CONCLUSIONS: There is substantial evidence for the clinical effectiveness of hospital at home but less evidence for virtual wards. Guidance for virtual wards is lacking on key aspects including team characteristics, outcome selection and data protection. We recommend that research and evaluation is integrated into development of virtual ward models. The issue of carer strain is particularly relevant.
Subject(s)
Hospitalization , State Medicine , Humans , Aged , Systematic Reviews as Topic , Hospitals , Treatment OutcomeABSTRACT
BACKGROUND: Studies investigating outcomes of delirium using large-scale routine data are rare. We performed a two-centre study using the 4 'A's Test (4AT) delirium detection tool to analyse relationships between delirium and 30-day mortality, length of stay and home time (days at home in the year following admission). METHODS: The 4AT was performed as part of usual care. Data from emergency admissions in patients ≥65 years in Lothian, UK (n = 43,946) and Salford, UK (n = 38,824) over a period of $\sim$3 years were analysed using logistic regression models adjusted for age and sex. RESULTS: 4AT completion rates were 77% in Lothian and 49% in Salford. 4AT scores indicating delirium (≥4/12) were present in 18% of patients in Lothian, and 25% of patients in Salford. Thirty-day mortality with 4AT ≥4 was 5.5-fold greater than the 4AT 0/12 group in Lothian (adjusted odds ratio (aOR) 5.53, 95% confidence interval [CI] 4.99-6.13) and 3.4-fold greater in Salford (aOR 3.39, 95% CI 2.98-3.87). Length of stay was more than double in patients with 4AT scores of 1-3/12 (indicating cognitive impairment) or ≥ 4/12 compared with 4AT 0/12. Median home time at 1 year was reduced by 112 days (Lothian) and 61 days (Salford) in the 4AT ≥4 group (P < 0.001). CONCLUSIONS: Scores on the 4AT used at scale in practice are strongly linked with 30-day mortality, length of hospital stay and home time. The findings highlight the need for better understanding of why delirium is linked with poor outcomes and also the need to improve delirium detection and treatment.
Subject(s)
Delirium , Aged , Delirium/diagnosis , Emergency Service, Hospital , Geriatric Assessment , Hospitals , Humans , Length of StaySubject(s)
Coronavirus Infections , Mental Disorders , Pandemics , Pneumonia, Viral , Betacoronavirus , COVID-19 , Humans , Mental Disorders/epidemiology , SARS-CoV-2 , United KingdomABSTRACT
PURPOSE: Quality improvement (QI) is a useful methodology that can be used to make timely improvements in clinical practice. This review gives a broad picture of what QI is and the methodology this entails. An overview of how QI has been applied in the field of delirium to date is provided as well as a discussion of how this area may be developed in the future. METHODS: As part of the review, a literature search was completed to assess the literature published to date on QI and delirium. Literature relating to delirium in the context of a variety of clinical specialties is also presented as well as a summary of short films that can be used for purposes of awareness raising. RESULTS: We found that QI has so far been an under-utilized methodology in the context of delirium and that studies that adhere to general guidance on reporting are few. CONCLUSION: We suggest that well-designed QI studies would be beneficial to improve the assessment, management and care of delirium. The methodology may also be used to embed educational resources. In this review, we describe the theory behind QI and also suggest some resources that may be useful in any QI delirium project.
Subject(s)
Delirium , Quality Improvement , Delirium/diagnosis , HumansABSTRACT
Phenylketonuria (PKU) is a metabolic condition which, left untreated, results in severe and irreversible brain damage. Newborn screening and the development of the low phenylalanine (Phe) diet have transformed the outcomes for people with PKU. Those who have benefited from early treatment are now approaching their fifth and sixth decade. It is therefore timely to consider multi-morbidity in PKU and the effects of ageing, in parallel with the wider benefits of emerging treatment options in addition to dietary relaxation. We have conducted the first literature review of co-morbidity and ageing in the context of PKU. Avenues explored have emerged from limited study of multi-morbidity to date and the knowledge and critical enquiry of the authors. Findings suggest PKU to have a wider impact than brain development, and result in several intriguing questions that require investigation to attain the best outcomes for people with PKU in adulthood moving through to older age. We recognise the difficulty in studying longitudinal outcomes in rare diseases and emphasise the necessity to develop PKU registries and cohorts that facilitate well-designed studies to answer some of the questions raised in this review. Whilst awaiting new information in these areas we propose that clinicians engage with patients to make personalised and well-informed decisions around Phe control and assessment for co-morbidity.
Subject(s)
Aging , Comorbidity , Phenylketonurias/diagnosis , Phenylketonurias/physiopathology , Adult , Aged , Humans , Infant, Newborn , Neonatal Screening , Phenylalanine/bloodABSTRACT
Sporadic Alzheimer's disease (AD) is a neurodegenerative disorder that causes the most prevalent form of age-related dementia but its pathogenesis remains obscure. Altered regulation of metals, particularly pan-cerebral copper deficiency, and more regionally-localized perturbation of other metals, are prominent in AD brain although data on how these CNS perturbations are reflected in the peripheral bloodstream are inconsistent to date. To assess the potential use of metal dysregulation to generate biomarkers in AD, we performed a case-control study of seven essential metals and selenium, measured by inductively coupled plasma mass-spectrometry, in samples from AD and matched control cases. Metals were sodium, potassium, calcium, magnesium, iron, zinc, and copper. In the whole study-group and in female participants, plasma metal levels did not differ between cases and controls. In males by contrast, there was moderate evidence that zinc levels trended towards increase in AD [10.8 (10.2-11.5)] µmol/L, mean (± 95% CI; P = 0.021) compared with controls [10.2 (9.6-10.4)]. Thus alterations in plasma zinc levels differed between genders in AD. In correlational analysis, there was evidence for an increased number of 'strong' metal co-regulations in AD cases and differential co-modulations of metal pairs: copper-sodium (Rcontrol = - 0.03, RAD = 0.65; P = 0.009), and copper-calcium (Rcontrol = - 0.01, RAD = 0.65; P = 0.01) were significant in AD males, potentially consistent with reported evidence for dysregulation of copper in severely damaged brain regions in AD. In conclusion, our data suggest that the measurement of metals co-regulation in plasma may provide a useful representation of those metal perturbations taking place in the AD brain and therefore might be useful as plasma-based biomarkers.
Subject(s)
Alzheimer Disease/blood , Biomarkers/blood , Dementia/blood , Metals/blood , Calcium/blood , Copper/blood , Female , Humans , Iron/blood , Magnesium/blood , Male , Potassium/blood , Selenium/blood , Sex Characteristics , Sodium/blood , Zinc/bloodABSTRACT
Impairment of brain-glucose uptake and brain-copper regulation occurs in Alzheimer's disease (AD). Here we sought to further elucidate the processes that cause neurodegeneration in AD by measuring levels of metabolites and metals in brain regions that undergo different degrees of damage. We employed mass spectrometry (MS) to measure metabolites and metals in seven post-mortem brain regions of nine AD patients and nine controls, and plasma-glucose and plasma-copper levels in an ante-mortem case-control study. Glucose, sorbitol and fructose were markedly elevated in all AD brain regions, whereas copper was correspondingly deficient throughout (all P < 0.0001). In the ante-mortem case-control study, by contrast, plasma-glucose and plasma-copper levels did not differ between patients and controls. There were pervasive defects in regulation of glucose and copper in AD brain but no evidence for corresponding systemic abnormalities in plasma. Elevation of brain glucose and deficient brain copper potentially contribute to the pathogenesis of neurodegeneration in AD.
Subject(s)
Alzheimer Disease/metabolism , Blood Glucose/metabolism , Brain/metabolism , Copper/deficiency , Dementia/metabolism , Polymers/chemistry , Aged , Animals , Case-Control Studies , Copper/blood , Female , Fructose/chemistry , Glucose/chemistry , Humans , Male , Mass Spectrometry , Metals/chemistry , Mice , Mice, Inbred C57BL , Mice, Transgenic , Middle Aged , Probability , Rats , Rats, Wistar , Sorbitol/chemistry , Tissue DistributionABSTRACT
Parkinson's disease (PD) is common and has a number of associated neuropsychiatric disturbances. Of these, delirium has historically been under-recognised. Delirium is an acute disturbance of attention and awareness that fluctuates, and is accompanied by an additional disturbance of cognition. As delirium is known to carry a particularly poor prognosis in terms of morbidity and mortality, and the relationship between delirium and dementia is becoming better defined, we completed a literature review of delirium in the context of PD. A literature search was completed using the databases PubMed, Embase and Ovid Medline. PubMed (1945-2014) was searched in September 2014; Embase (1974-2014); and Ovid Medline (1946-2014) in October 2014. The search terms 'delirium' and 'Parkinsons' in combination were used. Large studies using a robust definition of delirium were lacking in PD. There is the suggestion that PD is a risk factor for delirium and that delirium negatively impacts upon the motor symptom trajectory. Deficits in the neurotransmitters dopamine and acetylcholine are implicated in the pathophysiology of delirium in PD. Systemic inflammation also appears to have a role. Treatment of delirium in PD should include medication review and cautious use of atypical antipsychotics where pharmacological treatment is indicated. Of the atypical antipsychotics studied, quetiapine has the least extrapyramidal side effects. Evidence suggests a specific link between delirium and PD but well-designed clinical studies to evaluate the prevalence, impact and treatment of delirium in PD are required. Given the potential to improve outcomes through delirium prevention we conclude that delirium in PD is an area worthy of further study.
Subject(s)
Comorbidity , Delirium , Parkinson Disease , Delirium/drug therapy , Delirium/epidemiology , Delirium/etiology , Humans , Parkinson Disease/complications , Parkinson Disease/epidemiologyABSTRACT
UNLABELLED: Pathologic deposition of amyloid ß (Aß) protein is a key component in the pathogenesis of Alzheimer disease (AD) but not a feature of frontotemporal dementia (FTD). PET ligands for Aß protein are increasingly used in diagnosis and research of dementia syndromes. Here, we report a PET study using (18)F-florbetapir in healthy controls and patients with AD and FTD. METHODS: Ten healthy controls (mean age ± SD, 62.5 ± 5.2 y), 10 AD patients (mean age ± SD, 62.6 ± 4.5), and 8 FTD patients (mean age ± SD, 62.5 ± 9.6) were recruited to the study. All patients underwent detailed clinical and neuropsychologic assessment and T1-weighted MR imaging and were genotyped for apolipoprotein E status. All participants underwent dynamic (18)F-florbetapir PET on a high-resolution research tomograph, and FTD patients also underwent (18)F-FDG PET scans. Standardized uptake value ratios (SUVRs) were extracted for predefined gray and white matter regions of interest using cerebellar gray matter as a reference region. Static PET images were evaluated by trained raters masked to clinical status and regional analysis. RESULTS: Total cortical gray matter (18)F-florbetapir uptake values were significantly higher in AD patients (median SUVR, 1.73) than FTD patients (SUVR, 1.13, P = 0.002) and controls (SUVR, 1.26, P = 0.04). (18)F-Florbetapir uptake was also higher in AD patients than FTD patients and controls in the frontal, parietal, occipital, and cingulate cortices and in the central subcortical regions. Only 1 FTD patient (homozygous for apolipoprotein E ε4) displayed high cortical (18)F-florbetapir retention, whereas (18)F-FDG PET demonstrated mesiofrontal hypometabolism consistent with the clinical diagnosis of FTD. Most visual raters classified 1 control (10%) and 8 AD (80%) and 2 FTD (25%) patients as amyloid-positive, whereas ratings were tied in another 2 FTD patients and 1 healthy control. CONCLUSION: Cortical (18)F-florbetapir uptake is low in most FTD patients, providing good discrimination from AD. However, visual rating of FTD scans was challenging, with a higher rate of discordance between interpreters than in AD and control subjects.
Subject(s)
Alzheimer Disease/diagnostic imaging , Aniline Compounds , Ethylene Glycols , Frontotemporal Dementia/diagnostic imaging , Positron-Emission Tomography , Aged , Alzheimer Disease/diagnosis , Alzheimer Disease/genetics , Amyloidogenic Proteins/chemistry , Apolipoproteins E/genetics , Case-Control Studies , Female , Fluorine Radioisotopes , Frontotemporal Dementia/diagnosis , Genotype , Humans , Magnetic Resonance Imaging , Male , Middle AgedABSTRACT
Dementia with Lewy bodies (DLB) is recognised as the second most common form of dementia in older people. Delirium is a condition of acute brain dysfunction for which a pre-existing diagnosis of dementia is a risk factor. Conversely delirium is associated with an increased risk of developing dementia. The reasons for this bidirectional relationship are not well understood. Our aim was to review possible similarities in the clinical presentation and pathophysiology between delirium and DLB, and explore possible links between these diagnoses. A systematic search using Medline, Embase and Psychinfo was performed. References were scanned for relevant articles, supplemented by articles identified from reference lists and those known to the authors. 94 articles were selected for inclusion in the review. Delirium and DLB share a number of clinical similarities, including global impairment of cognition, fluctuations in attention and perceptual abnormalities. Delirium is a frequent presenting feature of DLB. In terms of pathophysiological mechanisms, cholinergic dysfunction and genetics may provide a common link. Neuroimaging studies suggest a brain vulnerability in delirium which may also occur in dementia. The basal ganglia, which play a key role in DLB, have also been implicated in delirium. The role of Cerebrospinal fluid (CSF) and serum biomarkers for both diagnoses is an interesting area although some results are conflicting and further work in this area is needed. Delirium and DLB share a number of features and we hypothesise that delirium may, in some cases, represent early or 'prodromal' DLB. Further research is needed to test the novel hypothesis that delirium may be an early marker for future DLB, which would aid early diagnosis of DLB and identify those at high risk.
Subject(s)
Brain/metabolism , Delirium/diagnosis , Lewy Body Disease/diagnosis , Accidental Falls , Affective Symptoms/complications , Affective Symptoms/diagnosis , Biomarkers/blood , Biomarkers/cerebrospinal fluid , Biomarkers/metabolism , Brain/pathology , Cognition Disorders/complications , Cognition Disorders/diagnosis , Consciousness Disorders/complications , Consciousness Disorders/diagnosis , Delirium/blood , Delirium/cerebrospinal fluid , Delirium/genetics , Delirium/metabolism , Delirium/pathology , Delusions/complications , Delusions/diagnosis , Functional Neuroimaging , Humans , Lewy Body Disease/blood , Lewy Body Disease/cerebrospinal fluid , Lewy Body Disease/genetics , Lewy Body Disease/metabolism , Lewy Body Disease/pathology , Movement Disorders/complications , Movement Disorders/diagnosis , Perceptual Disorders/complications , Perceptual Disorders/diagnosis , Sleep Wake Disorders/complications , Sleep Wake Disorders/diagnosis , Syncope/complicationsABSTRACT
BACKGROUND: Alzheimer's disease (AD) is considered to be a disorder predominantly affecting memory. It is increasingly recognized that the cognitive profile may be heterogeneous. We hypothesized that it would be possible to define distinct "cognitive phenotypes" in older people with AD. METHODS: Participants from three individual studies were included, consisting of 109 patients with a diagnosis of probable AD, and 91 age- and gender-matched control participants. All had demographic and cognitive assessment data available, including the Cambridge Cognitive Examination of the Elderly (CAMCOG). The CAMCOG scores and sub-scores were further analyzed using hierarchical cluster analysis and factor analysis. RESULTS: Three clusters were identified. The scores loaded onto three factors representing the domains of attention, praxis, calculation, and perception; memory; and language comprehension and executive function. The main difference between the clusters related to degree of memory impairment. The composite score for memory between the clusters remained significantly different despite adjustment for illness duration and age of onset (p < 0.001). CONCLUSIONS: These data suggest clinical heterogeneity within an older group of people with AD. This may have implications for diagnosis, prognosis, response to currently available treatments, and the development of novel therapies.
Subject(s)
Alzheimer Disease/psychology , Cognition , Aged , Alzheimer Disease/classification , Attention , Case-Control Studies , Comprehension , Executive Function , Factor Analysis, Statistical , Female , Humans , Male , Memory , Neuropsychological Tests , Perception , PhenotypeABSTRACT
Alzheimer's disease (AD) is generally considered to be a disorder primarily affecting memory. It is increasingly recognized that the clinical presentation or "cognitive phenotype" is variable. The apolipoprotein E ε4 (APOE ε4) allele has been associated with an amnestic presentation, but does not appear to fully explain the high prevalence of family history within this group. We examined polymorphisms in the genes ACE and IDE in relation to cognitive phenotype. In this study 276 participants with AD were categorized into 1 of 4 cognitive phenotype classifications: typical, amnestic, language, and posterior. Family history and possession of the APOE ε4 allele were most prevalent in the amnestic group. Of the 10 genetic variants of IDE, and the 3 genetic variants of ACE studied, only ACErs4291 and ACErs1800764 were nominally associated with the amnestic presentation.
Subject(s)
Alzheimer Disease/genetics , Cognition Disorders/genetics , Genetic Variation/genetics , Insulysin/genetics , Peptidyl-Dipeptidase A/genetics , Phenotype , Alzheimer Disease/diagnosis , Cognition Disorders/diagnosis , Female , Genetic Predisposition to Disease/genetics , Humans , MaleABSTRACT
BACKGROUND: Tissue non-specific alkaline phosphatase (TNAP) has been shown to promote the neurotoxicity of extracellular tau which contributes to the spread of pathology in Alzheimer's disease (AD). OBJECTIVE: To investigate changes in TNAP activity in the hippocampus in both sporadic and familial AD, and to examine whether changes in neuronal TNAP are reflected systemically by looking at changes in plasma TNAP activity in AD. METHODS: We measured the activity of TNAP in the hippocampus in sporadic AD, familial AD and appropriate age-matched controls, and in an ageing series (age: 25-88 years) of brains. In addition, we measured TNAP activity in plasma from 110 AD and 110 non-demented control participants. RESULTS: TNAP activity was significantly increased in the hippocampus in sporadic (by 56%; p = 0.038) and familial AD (by 121%; p = 0.042) compared with the age-matched controls. However, there was no correlation of TNAP activity with age. Furthermore, plasma TNAP activity was increased in AD (by 13%; p = 0.018) and inversely correlated with cognitive function (r(s) = -0.211; p = 0.027). CONCLUSION: Together, these data indicate that TNAP is increased in both sporadic and familial AD but not in the aged brain, indicating that the increase is likely a consequence of AD-associated changes in the brain. The neuronal change in TNAP is reflected in an increase in plasma TNAP in AD and is inversely correlated with cognitive function.
Subject(s)
Alkaline Phosphatase/metabolism , Alzheimer Disease/enzymology , Alzheimer Disease/metabolism , Hippocampus/metabolism , Adult , Aged , Aged, 80 and over , Aging/metabolism , Alkaline Phosphatase/blood , Alzheimer Disease/blood , Case-Control Studies , Cognition/physiology , Female , Humans , Male , Middle AgedABSTRACT
We sought to identify new susceptibility loci for Alzheimer's disease through a staged association study (GERAD+) and by testing suggestive loci reported by the Alzheimer's Disease Genetic Consortium (ADGC) in a companion paper. We undertook a combined analysis of four genome-wide association datasets (stage 1) and identified ten newly associated variants with P ≤ 1 × 10(-5). We tested these variants for association in an independent sample (stage 2). Three SNPs at two loci replicated and showed evidence for association in a further sample (stage 3). Meta-analyses of all data provided compelling evidence that ABCA7 (rs3764650, meta P = 4.5 × 10(-17); including ADGC data, meta P = 5.0 × 10(-21)) and the MS4A gene cluster (rs610932, meta P = 1.8 × 10(-14); including ADGC data, meta P = 1.2 × 10(-16)) are new Alzheimer's disease susceptibility loci. We also found independent evidence for association for three loci reported by the ADGC, which, when combined, showed genome-wide significance: CD2AP (GERAD+, P = 8.0 × 10(-4); including ADGC data, meta P = 8.6 × 10(-9)), CD33 (GERAD+, P = 2.2 × 10(-4); including ADGC data, meta P = 1.6 × 10(-9)) and EPHA1 (GERAD+, P = 3.4 × 10(-4); including ADGC data, meta P = 6.0 × 10(-10)).
Subject(s)
ATP-Binding Cassette Transporters/genetics , Adaptor Proteins, Signal Transducing/genetics , Alzheimer Disease/genetics , Antigens, CD/genetics , Antigens, Differentiation, Myelomonocytic/genetics , Cytoskeletal Proteins/genetics , Membrane Proteins/genetics , Receptor, EphA1/genetics , Aged , Aged, 80 and over , Case-Control Studies , Databases, Genetic , Female , Genetic Predisposition to Disease , Genetic Variation , Genome-Wide Association Study , Humans , Male , Multigene Family , Polymorphism, Single Nucleotide , Sialic Acid Binding Ig-like Lectin 3ABSTRACT
The insertion allele in the gene encoding angiotensin-converting enzyme (ACE) is a risk factor for Alzheimer's disease (AD) and ACE is one of several peptidases that have the ability to degrade the neurotoxic amyloid-beta peptide. ACE is a membrane-bound peptidase that is also present in a soluble form in plasma as a result of a zinc metalloprotease-mediated shedding event. Here we aimed to determine whether there is a difference in ACE in the plasma of late-onset clinically diagnosed AD patients (n = 94) as compared to age-matched non-demented control subjects (n = 188). Plasma ACE was lower in the AD subjects as compared to the controls both at baseline (p = 0.072) and after two years (p = 0.05). There was a greater reduction in plasma ACE in the AD subjects as compared to the control subjects over the two years. Plasma ACE did not correlate with cognitive function. The observed reduction in plasma ACE in AD may reflect a general decrease in the zinc metalloprotease-mediated shedding of a subset of membrane-bound proteins.
Subject(s)
Alzheimer Disease/genetics , Alzheimer Disease/metabolism , Peptidyl-Dipeptidase A/blood , Peptidyl-Dipeptidase A/genetics , Age of Onset , Aged , Alzheimer Disease/epidemiology , Apolipoprotein E4/genetics , Biomarkers/blood , Female , Genetic Linkage , Genotype , Humans , Male , Metalloproteases/metabolism , ROC Curve , Risk Factors , Zinc/metabolismABSTRACT
BACKGROUND: Insulin-like growth factor (IGF)-1 has been implicated in the pathogenesis of Alzheimer's disease (AD). METHODS: We compared the level of circulating total and bioavailable IGF-1, by simultaneous measurements of IGF-1 and IGF binding protein (IGFBP)-3, between 87 patients diagnosed with AD and 126 age and sex matched control subjects without cognitive impairment. Blood samples were collected and IGF-1 and IGFBP-3 measured by ELISA. Subjects were also genotyped for apolipoprotein E. RESULTS: Total circulating IGF-1 levels were significantly raised in the AD group as compared to the control group (p=0.022). There was no significant difference in the circulating level of IGFBP-3 between the two groups. When the IGF-1 levels were ratioed against IGFBP-3 levels as an indicator of unbound, bioavailable circulating IGF-1, there was a significant increase in the molar IGF-1:IGFBP-3 ratio in the AD subjects (0.181 +/- 0.006) as compared to the controls (0.156 +/- 0.004) (p< 0.001). Logistic regression analysis revealed that an increase in the IGF-1:IGFBP-3 molar ratio increased the risk of AD significantly. CONCLUSION: The results of increased total and free circulating IGF-1 support the hypothesis that in its early stages late-onset AD reflects a state of resistance to IGF-1.