Trends in the incidence of dementia: design and methods in the Alzheimer Cohorts Consortium

Prevalence and risk factors for dementia in the Tibetan region: A population-based cross-sectional study

BACKGROUND

As China's population ages, the nationwide prevalence of dementia is increasing. However, the epidemiology of dementia among the Tibetan population remains unclear.

OBJECTIVE

A cross-sectional study was conducted involving 9116 participants aged >50 years in the Tibetan population to investigate the risk factors and prevalence of dementia among this population. Permanent residents of the region were invited to participate, and the response rate was 90.7 %.

METHODS

The participants underwent neuropsychological testing and clinical assessments, from which physical measurements (e.g., body mass index, blood pressure), demographic information (e.g., gender, age), and lifestyle details (e.g., family living arrangement, smoking, alcohol arrangement) were recorded. Dementia diagnoses were made using the standard consensus diagnostic criteria. The risk factors of dementia were identified using stepwise multiple logistic regression.

RESULTS

The average age of the participants was 63.71 (standard deviation = 9.36), and there were 44.86 % males. The prevalence of dementia was 4.66 %. The multivariate logistic regression analysis revealed that older age, unmarried status, lower education level, obesity, hypertension, diabetes, coronary heart disease, cerebral vascular disease, and HAPC were independently and positively associated with dementia (P < 0.05). However, no association was found between the frequency of religious activities and the prevalence of dementia in this population (P > 0.05).

CONCLUSIONS

There exist a number of contributory risk factors for dementia in the Tibetan population, with variations associated with high altitude, religious activities (i.e., scripture turning, chanting, spinning Buddhist beads, and bowing), and dietary habits. These findings suggest that social activities, such as religious activities, are protective factors for dementia.

Dementia prevention: The potential long-term cost-effectiveness of the FINGER prevention program

INTRODUCTION

The aim of this study was to estimate the potential cost-effectiveness of the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) program.

METHODS

A life-time Markov model with societal perspective, simulating a cohort of people at risk of dementia reflecting usual care and the FINGER program.

RESULTS

Costs were 1,653,275 and 1,635,346 SEK and quality-adjusted life years (QALYs) were 8.636 and 8.679 for usual care and the FINGER program, respectively, resulting in savings of 16,928 SEK (2023 US$) and 0.043 QALY gains per person, supporting extended dominance for the FINGER program. A total of 1623 dementia cases were avoided with 0.17 fewer person-years living with dementia. The sensitivity analysis confirmed the conclusions in most scenarios.

DISCUSSION

The model provides support that programs like FINGER have the potential to be cost-effective in preventing dementia. Results at the individual level are rather modest, but the societal benefits can be substantial because of the large potential target population.

Feasibility, Reliability, and Validity of the Vietnamese Version of the Clinical Dementia Rating

INTRODUCTION

In Vietnam, Alzheimer's disease (AD) and other dementias have become an increasingly important public health problem among the elderly. Achieving a diagnosis tool with high reliability and validity is essential. The Clinical Dementia Rating (CDR) is a global clinical scale with established diagnostic and severity-ranking utility that has been widely employed in epidemiological studies in an international context.

OBJECTIVE

The aims of this study were to establish the Vietnamese version of the CDR (V-CDR) and evaluate the feasibility, reliability, and validity of this version for diagnosing and classifying cognitive functions in the elderly.

METHOD

One hundred and fifty-three elderly outpatients at a clinic of Cho Ray Hospital, Vietnam, were screened with the Mini Mental State Examination (MMSE) for potential cognitive impairment. All those who scored ≤26 points were included in the study and were subsequently remitted to the V-CDR and clinical assessment for diagnosis. Reliability was assessed through internal consistency (Cronbach α), intra- and interrater reliability (weighted κ). Concurrent and discriminative validity of the V-CDR were assessed.

RESULTS

The V-CDR had an excellent internal consistency for each of the 2 raters (Cronbach α 0.90 and 0.96) and excellent agreement in both intra- and interrater reliability (weighted κ 0.84 [95% CI 0.74-0.94] and 0.82 [95% CI 0.72-0.93], respectively). The sensitivity and specificity for detecting dementia were 93.6 and 100%, respectively. The positive and negative predictive value were 100 and 96.4%, respectively. The agreement of V-CDR and clinical assessment was excellent (weighted κ 0.94 [95% CI 0.88-0.99]). V-CDR was substantially better than MMSE at distinguishing between mild cognitive impairment and normal cognitive function (AUC = 0.957, 95% CI 0.893-1.000 vs. AUC 0.594, 95% CI 0.441-0.746).

CONCLUSIONS

The V-CDR is a feasible, reliable, and valid instrument which should be used in clinical practice for diagnosing and classifying the different dementia stages in the elderly.

Population-Based Studies in Dementia and Ageing Research: A Local and National Experience in Cambridgeshire and the UK

Dementia has been recognised as a key challenge in many ageing societies across the world. Several population-based studies have been developed to investigate dementia and cognitive ageing from perspectives of biology, health, psychology and social sciences. However, there is a need to provide a better understanding of 'contexts', the circumstance where these ageing populations existed, and heterogeneity within and across the populations in different time and places. In this article, we summarise some examples of earlier population-based studies undertaken by our research groups in England and Wales and their contribution to the epidemiology of dementia, neuropathology, cognitive and mental health in older age. We also describe how these studies illustrated variation among ageing populations and changes in their health conditions across time and place. These findings highlight the contribution that population-based studies can make, along with the vital to incorporate contexts in ageing research. A lifecourse approach within social context is needed to integrate life experiences, social circumstances, and multiple dimensions of cognition, functioning, physical health and wellbeing over the ageing process. We also discuss how evidence from population-based studies can support various international initiatives on dementia, healthy ageing and Sustainable Development Goals and facilitate tailored approaches for diverse populations across global societies.

Connecting Cohorts to Diminish Alzheimer's Disease (CONCORD-AD): A Report of an International Research Collaboration Network

Longitudinal observational cohort studies are being conducted worldwide to understand cognition, biomarkers, and the health of the aging population better. Cross-cohort comparisons and networks of registries in Alzheimer’s disease (AD) foster scientific exchange, generate insights, and contribute to the evolving clinical science in AD. A scientific working group was convened with invited investigators from established cohort studies in AD, in order to form a research collaboration network as a resource to address important research questions. The Connecting Cohorts to Diminish Alzheimer’s Disease (CONCORD-AD) collaboration network was created to bring together global resources and expertise, to generate insights and improve understanding of the natural history of AD, to inform design of clinical trials in all disease stages, and to plan for optimal patient access to disease-modifying therapies once they become available. The network brings together expertise and data insights from 7 cohorts across Australia, Europe, and North America. Notably, the network includes populations recruited through memory clinics as well as population-based cohorts, representing observations from individuals across the AD spectrum. This report aims to introduce the CONCORD-AD network, providing an overview of the cohorts involved, reporting the common assessments used, and describing the key characteristics of the cohort populations. Cohort study designs and baseline population characteristics are compared, and available cognitive, functional, and neuropsychiatric symptom data, as well as the frequency of biomarker assessments, are summarized. Finally, the challenges and opportunities of cross-cohort studies in AD are discussed.

Association between depressive symptoms, metabolic risk factors, and cognitive function: cross-sectional results from a community study in Quebec, Canada

OBJECTIVE

To investigate the cross-sectional association between depressive symptoms and metabolic risk factors with cognitive function in a middle-aged population.

METHODS

A stratified subsample of the CARTaGENE (CaG) cohort (n = 1991) was used to compare cognitive function outcomes between groups. The stratification was based on the presence of depressive symptoms and metabolic dysregulation (MetD): the presence of a) neither condition (reference group); b) MetD only; c) depressive symptoms only; and d) both depressive symptoms and MetD. Individuals with type 2 diabetes were excluded. Three cognitive domains were assessed: processing speed, episodic memory, and executive function. An overall cognitive function score, standardized for age and education, was computed. Poor cognitive function was defined as the lower quartile of the overall cognitive function distribution. Linear and logistic regression analyses were conducted.

RESULTS

The poorest cognitive performance was observed in the group with both depressive symptoms and MetD, followed by the group with depressive symptoms only, then the group with MetD only and the reference group. Mean (SD) overall cognition scores for the four groups were -0.25 (1.13), -0.13 (1.05), 0.11 (0.90), and 0.15 (0.93), respectively. Linear regression analyses suggested a linear increase in cognitive function across groups.In the logistic regression analyses, the highest risk of poor cognitive function was observed in the comorbid (depressive symptoms and MetD) group (adjusted OR = 1.99, 95% CI 1.46, 2.71).

CONCLUSION

Comorbidity of depressive symptoms and MetD was associated with reduced cognitive performance in middle-aged adults without diabetes.KEY POINTSPoor cognitive function is a major public health concern and can be potentially prevented by targeting its modifiable risk factors.Metabolic dysregulation and depression have both been independently associated with poor cognitive function.Comorbidity of metabolic dysregulation and depressive symptoms is associated with an increased risk of poor cognitive function in middle-aged individuals.Future health interventions might benefit by screening for comorbidity in patients with poor cognitive function and by targeting depression and metabolic dysregulation together.

Polysaccharide of Taxus chinensis var. mairei Cheng et L.K.Fu attenuates neurotoxicity and cognitive dysfunction in mice with Alzheimer's disease

CONTEXT

Polysaccharide of Taxus chinensis var. mairei Cheng et L.K.Fu (Taxaceae) (PTM) functions in anti-apoptosis and antioxidation, but its function on Alzheimer's disease (AD) remains unclear.

OBJECTIVE

To investigate the effect of PTM on AD.

MATERIALS AND METHODS

C57BL/6J mice were randomly divided into three groups: control, d-galactose (d-gal), and d-gal + PTM. AD-like symptom was induced by d-gal for 6 weeks, followed with PTM (0.4 g/kg/d) for 14 days. PTM was added to BV2 cells stimulated with d-gal (1, 10, 20, 50, 100 and 500 μg/mL). Cell viability was evaluated by MTT assay. The expression of NRF2, SOD, cleaved caspase-3, Bax and Bcl-2 were detected with Western blot analysis. Cognitive function was evaluated by Morris water maze test.

RESULTS

Decreased cleaved caspase-3 (1.30 ± 0.09) and Bax/Bcl2 ratio (1.32 ± 0.11) were observed in BV2 cells induced by d-gal + PTM (50 μg/mL). Increased MDA and ROS and decreased SOD were observed in d-gal group. However, decreased MDA (175 ± 9 ng/mL) and ROS level (188 ± 38 ng/mL) were observed after treated with PTM group (p < 0.05). In addition, the expression of NRF2 decreased in d-gal group (0.75 ± 0.09) but increased after treated with PTM (p < 0.05). Furthermore, decreased Aβ1-42 was observed and the cognitive function was improved after PTM intervention (p < 0.05).

CONCLUSIONS

This is the first report that PTM inhibited oxidative stress and apoptosis in AD. The result will further accelerate the applications of Taxus chinensis var. mairei and the treatment for AD.

Catecholamines in Alzheimer's Disease: A Systematic Review and Meta-Analysis

Background and Purpose: Previous studies found inconsistent results regarding the relationship between Alzheimer's disease (AD) and catecholamines, such as dopamine (DA), norepinephrine (NE), and epinephrine (EPI). Therefore, the purpose of this study was to perform a systematic review and meta-analysis to evaluate the results of previous studies on this relationship.

Method: Literature retrieval of eligible studies was performed in four databases (Web of Science, PubMed, Embase, and PsycARTICLES). Standardized mean differences (SMDs) were calculated to assess differences in catecholamine concentrations between the AD groups and controls.

Results: Thirteen studies met the eligibility criteria. Compared with the controls, significant lower concentrations of NE (SMD = −1.10, 95% CI: −2.01 to −0.18, p = 0.019) and DA (SMD = −1.12, 95% CI: −1.88 to −0.37, p = 0.003) were observed in patients with AD. No difference was found in the concentrations of EPI between the two groups (SMD = −0.74, 95% CI: −1.85 to 0.37, p = 0.189).

Conclusion: Overall, these findings are in line with the hypothesis that reduced NE and DA may be an important indicator for AD (Registration number CRD42018112816).

Twenty-seven-year time trends in dementia incidence in Europe and the United States: The Alzheimer Cohorts Consortium

OBJECTIVE

To determine changes in the incidence of dementia between 1988 and 2015.

METHODS

This analysis was performed in aggregated data from individuals >65 years of age in 7 population-based cohort studies in the United States and Europe from the Alzheimer Cohort Consortium. First, we calculated age- and sex-specific incidence rates for all-cause dementia, and then defined nonoverlapping 5-year epochs within each study to determine trends in incidence. Estimates of change per 10-year interval were pooled and results are presented combined and stratified by sex.

RESULTS

Of 49,202 individuals, 4,253 (8.6%) developed dementia. The incidence rate of dementia increased with age, similarly for women and men, ranging from about 4 per 1,000 person-years in individuals aged 65-69 years to 65 per 1,000 person-years for those aged 85-89 years. The incidence rate of dementia declined by 13% per calendar decade (95% confidence interval [CI], 7%-19%), consistently across studies, and somewhat more pronouncedly in men than in women (24% [95% CI 14%-32%] vs 8% [0%-15%]).

CONCLUSION

The incidence rate of dementia in Europe and North America has declined by 13% per decade over the past 25 years, consistently across studies. Incidence is similar for men and women, although declines were somewhat more profound in men. These observations call for sustained efforts to finding the causes for this decline, as well as determining their validity in geographically and ethnically diverse populations.

Plasma tau, neurofilament light chain and amyloid-β levels and risk of dementia; a population-based cohort study

CSF biomarkers, including total-tau, neurofilament light chain (NfL) and amyloid-β, are increasingly being used to define and stage Alzheimer’s disease. These biomarkers can be measured more quickly and less invasively in plasma and may provide important information for early diagnosis of Alzheimer’s disease. We used stored plasma samples and clinical data obtained from 4444 non-demented participants in the Rotterdam study at baseline (between 2002 and 2005) and during follow-up until January 2016. Plasma concentrations of total-tau, NfL, amyloid-β₄₀ and amyloid-β₄₂ were measured using the Simoa NF-light^® and N3PA assays. Associations between biomarker plasma levels and incident all-cause and Alzheimer’s disease dementia during follow-up were assessed using Cox proportional-hazard regression models adjusted for age, sex, education, cardiovascular risk factors and APOE ε4 status. Moreover, biomarker plasma levels and rates of change over time of participants who developed Alzheimer’s disease dementia during follow-up were compared with age and sex-matched dementia-free control subjects. During up to 14 years follow-up, 549 participants developed dementia, including 374 cases with Alzheimer’s disease dementia. A log₂ higher baseline amyloid-β₄₂ plasma level was associated with a lower risk of developing all-cause or Alzheimer’s disease dementia, adjusted hazard ratio (HR) 0.61 [95% confidence interval (CI), 0.47–0.78; P < 0.0001] and 0.59 (95% CI, 0.43–0.79; P = 0.0006), respectively. Conversely, a log₂ higher baseline plasma NfL level was associated with a higher risk of all-cause dementia [adjusted HR 1.59 (95% CI, 1.38–1.83); P < 0.0001] or Alzheimer’s disease [adjusted HR 1.50 (95% CI, 1.26–1.78); P < 0.0001]. Combining the lowest quartile group of amyloid-β₄₂ with the highest of NfL resulted in a stronger association with all-cause dementia [adjusted HR 9.5 (95% CI, 2.3–40.4); P < 0.002] and with Alzheimer’s disease [adjusted HR 15.7 (95% CI, 2.1–117.4); P < 0.0001], compared to the highest quartile group of amyloid-β₄₂ and lowest of NfL. Total-tau and amyloid-β₄₀ levels were not associated with all-cause or Alzheimer’s disease dementia risk. Trajectory analyses of biomarkers revealed that mean NfL plasma levels increased 3.4 times faster in participants who developed Alzheimer’s disease compared to those who remained dementia-free (P < 0.0001), plasma values for cases diverged from controls 9.6 years before Alzheimer’s disease diagnosis. Amyloid-β₄₂ levels began to decrease in Alzheimer’s disease cases a few years before diagnosis, although the decline did not reach significance compared to dementia-free participants. In conclusion, our study shows that low amyloid-β₄₂ and high NfL plasma levels are each independently and in combination strongly associated with risk of all-cause and Alzheimer’s disease dementia. These data indicate that plasma NfL and amyloid-β₄₂ levels can be used to assess the risk of developing dementia in a non-demented population. Plasma NfL levels, although not specific, may also be useful in monitoring progression of Alzheimer’s disease dementia.

Sex and gender differences in Alzheimer's disease: current challenges and implications for clinical practice: Position paper of the Dementia and Cognitive Disorders Panel of the European Academy of Neurology

Alzheimer's disease (AD) is characterized by high heterogeneity in disease manifestation, progression and risk factors. High phenotypic variability is currently regarded as one of the largest hurdles in early diagnosis and in the design of clinical trials; there is therefore great interest in identifying factors driving variability that can be used for patient stratification. In addition to genetic and lifestyle factors, the individual's sex and gender are emerging as crucial drivers of phenotypic variability. Evidence exists on sex and gender differences in the rate of cognitive deterioration and brain atrophy, and in the effect of risk factors as well as in the patterns of diagnostic biomarkers. Such evidence might be of high relevance and requires attention in clinical practice and clinical trials. However, sex and gender differences are currently seldom appreciated; importantly, consideration of sex and gender differences is not currently a focus in the design and analysis of clinical trials for AD. The objective of this position paper is (i) to provide an overview of known sex and gender differences that might have implications for clinical practice, (ii) to identify the most important knowledge gaps in the field (with a special regard to clinical trials) and (iii) to provide conclusions for future studies. This scientific statement is endorsed by the European Academy of Neurology.

Epidemiology of neurological diseases in older adults

Neurological diseases refer to the diseases that target the nervous system (brain, spine or nerves). They are the second leading cause of death, and the first cause of severe long-term disability in the world. The prevalence of most neurological diseases increases sharply with age, and age also modulates the impact of risk factors, clinical presentation and the natural course of these diseases. Longitudinal population-based studies provide useful insights for a better understanding of the specificities of neurological diseases in older adults by assessment of a wide range of risk factors. Rapid population aging, especially in low-income countries, presents challenges in terms of health and social care. A multidisciplinary approach is necessary to find solutions to tackle the burden of neurological diseases in older adults.

Chemical sensing platforms for detecting trace-level Alzheimer's core biomarkers

This review provides an overview of recent advances in optical and electrical detection of Alzheimer's disease biomarkers in clinically relevant fluids.

Failures in Protein Clearance Partly Underlie Late Onset Neurodegenerative Diseases and Link Pathology to Genetic Risk

As we identify the loci involved in late onset neurodegenerative disease, we are finding that the majority of them are involved in damage response processes. In this short review, I propose that it is partly a failure in these damage response processes which underlie late onset disease and that the resultant pathology is a marker of the type of damage response which has failed: microglial clearance of damaged neuronal membranes in Alzheimer's disease (AD), ubiquitin proteasome clearance in the tauopathies, and lysosomal clearance in Parkinson's disease (PD). In this review, I outline this relationship. This article is not intended as a comprehensive review of the cell biology of any of these disorders but rather a summary of the evidence that the genetics and pathology of these disorders appear to point, in each case, to the removal of misfolded proteins as a critical process in disease pathogenesis.

Thirty-year trends in dementia: a nationwide population study of Swedish inpatient records

Background

The continuous growth of the current dementia epidemic is contingent on the stability of age- and sex-specific trends over time. However, recent evidence suggests declining or stable trends. The aim of this study was to evaluate the real-world changes in the burden of dementia in older adults in Sweden from 1987 to 2016 by estimating age- and sex-specific incidence of dementia diagnosis in hospital inpatient records (dementia incidence). Differences in trends by sex, age, and educational levels were also examined.

Methods

The entire Swedish population aged 65 years and older was followed up from 1987 to 2016. Age-, sex-, and education-stratified dementia incidence rates for every follow-up year were estimated using the National Patient Register. Hazard ratio of receiving a dementia diagnosis in the inpatient records per 1 calendar year increase was estimated with discrete time logistic models with a complementary log–log link.

Results

After increase, especially in those >85 years of age, dementia incidence started to decrease in the last 5 years of the study period. After 2011, 1 calendar year increase was associated with lower hazard ratio of receiving a hospital diagnosis of dementia. The decrease had the highest magnitude in 70–74-year-olds (−5.5%), followed by 75–79-year-olds (−4.5%) and 80–84-year-olds (−4.0%). The decrease was present in both sexes and at all educational levels up to 90 years of age. Age was associated with the level of dementia incidence, and the trends differed by age group. Educational gradient was observed. University-educated older adults had the lowest rates of dementia. However, the trend over time did not substantially differ by sex or educational level.

Conclusion

Our results provide more evidence that dementia incidence may be declining. They also suggest that at least in hospitals, the number of new patients with dementia may decrease in the future.

SIRT1, miR-132 and miR-212 link human longevity to Alzheimer's Disease

Alzheimer's Disease (AD) is the most common cause of dementia in the elderly. Centenarians - reaching the age of >100 years while maintaining good cognitive skills - seemingly have unique biological features allowing healthy aging and protection from dementia. Here, we studied the expression of SIRT1 along with miR-132 and miR-212, two microRNAs known to regulate SIRT1, in lymphoblastoid cell lines (LCLs) from 45 healthy donors aged 21 to 105 years and 24 AD patients, and in postmortem olfactory bulb and hippocampus tissues from 14 AD patients and 20 age-matched non-demented individuals. We observed 4.0-fold (P = 0.001) lower expression of SIRT1, and correspondingly higher expression of miR-132 (1.7-fold; P = 0.014) and miR-212 (2.1-fold; P = 0.036), in LCLs from AD patients compared with age-matched healthy controls. Additionally, SIRT1 expression was 2.2-fold (P = 0.001) higher in centenarian LCLs compared with LCLs from individuals aged 56-82 years; while centenarian LCLs miR-132 and miR-212 indicated 7.6-fold and 4.1-fold lower expression, respectively. Correlations of SIRT1, miR-132 and miR-212 expression with cognitive scores were observed for AD patient-derived LCLs and postmortem AD olfactory bulb and hippocampus tissues, suggesting that higher SIRT1 expression, possibly mediated by lower miR-132 and miR-212, may protect aged individuals from dementia and is reflected in their peripheral tissues.

The development of a stochastic mathematical model of Alzheimer's disease to help improve the design of clinical trials of potential treatments

Alzheimer's disease (AD) is a neurodegenerative disorder characterised by a slow progressive deterioration of cognitive capacity. Drugs are urgently needed for the treatment of AD and unfortunately almost all clinical trials of AD drug candidates have failed or been discontinued to date. Mathematical, computational and statistical tools can be employed in the construction of clinical trial simulators to assist in the improvement of trial design and enhance the chances of success of potential new therapies. Based on the analysis of a set of clinical data provided by the Alzheimer's Disease Neuroimaging Initiative (ADNI) we developed a simple stochastic mathematical model to simulate the development and progression of Alzheimer's in a longitudinal cohort study. We show how this modelling framework could be used to assess the effect and the chances of success of hypothetical treatments that are administered at different stages and delay disease development. We demonstrate that the detection of the true efficacy of an AD treatment can be very challenging, even if the treatment is highly effective. An important reason behind the inability to detect signals of efficacy in a clinical trial in this therapy area could be the high between- and within-individual variability in the measurement of diagnostic markers and endpoints, which consequently results in the misdiagnosis of an individual's disease state.