Subjective cognitive decline is related to CSF biomarkers of AD in patients with MCI

Accelerated long-term forgetting: from subjective memory decline to a defined clinical entity

Subjective memory decline (SMD) might represent the preclinical phase of Alzheimer's disease (AD), and has been reported in epileptic amnesia associated with accelerated long-term forgetting (ALF). We investigated ALF in SMD subjects by means of RAVLT recall and recognition and ROCF recall after 1-week retention and compared with a control group. Two-way ANOVAs for RAVLT and ROCF were conducted, and stepwise regression analysis was administered considering EMQ and DASS-21 as factors. SMD subjects performed significantly worse than controls at 1-week delay on RAVLT recall and recognition, but not on ROCF, and not associated with depression or memory complaints. SMD patients showed ALF, which is usually associated with temporomesial dysfunctions, representing a cognitive marker to assess objectively memory problems in SMD, and to undisclose initial neurodegenerative disease involving temporal structures usually compromised in AD. Therefore, SMD might no longer be "subjective," but rather a specific and defined clinical entity.

Reduced tactile sensitivity is associated with mild cognitive impairment

BACKGROUND

Sensory impairment has been related to age-associated cognitive decline. While these associations were investigated primarily in the auditory and visual domain, other senses such as touch have rarely been studied. Thus, it remains open whether these results are specific for particular sensory domains, or rather point to a fundamental role of sensory deficits in cognitive decline.

METHODS

Data from 31 participants with mild cognitive impairment (MCI), 46 participants with frailty, and 23 non-clinical control participants (NCCs) were included. We assessed sensory function using visual acuity and contrast sensitivity, hearing threshold, and mechanical detection threshold. Cognitive function in participants with MCI was assessed using associative memory performance. Group differences on sensory thresholds were tested using analyses of covariance with age, sex, and years of education as covariates. Associations between measures within participants with MCI were evaluated using Spearman correlations.

FINDINGS

We found a significant difference in mechanical detection threshold between the groups (p < 0.001, η2 = 0.18). Participants with MCI showed significantly reduced tactile sensitivity compared to participants with frailty and NCCs. In participants with MCI, lower associative memory performance was significantly related to reduced tactile sensitivity (rs = 0.39, p = 0.031) and auditory acuity (rs = 0.41, p = 0.022).

INTERPRETATION

Our results indicate that reduced tactile sensitivity is related to cognitive decline. Prospective studies should investigate the age-related alterations of multimodal sensory processes and their contribution to dementia-related processes.

FUNDING

Deutsche Forschungsgemeinschaft (FL 156/41-1) and a grant of the Hector-Stiftung II, Weinheim, Germany.

Sex and Education Modify the Association Between Subjective Cognitive Decline and Amyloid Pathology

Background

Subjective cognitive decline (SCD) may be an early risk factor for dementia, particularly in highly educated individuals and women. This study examined the effect of education and sex on the association between SCD and Alzheimer's disease (AD) biomarkers in non-demented older adults.

Method

Vanderbilt Memory and Aging Project participants free of clinical dementia or stroke (n=156, 72±6 years, 37% mild cognitive impairment, 33% female) completed fasting lumbar puncture, SCD assessment, and Wide Range Achievement Test-III Reading subtest to assess reading level at baseline as a a proxy for educational quality. Cerebrospinal fluid (CSF) biomarkers for AD (β-amyloid 42 (Aβ42), Aβ42/40 ratio, phosphorylated tau (p-tau), tau, and neurofilament light (NfL)) were analyzed in batch. Linear mixed effects models related SCD to CSF AD biomarkers and follow-up models assessed SCD x sex, SCD x reading level , and SCD x education interactions on AD biomarkers.

Result

In main effect models, higher SCD was associated with lower Aβ42 and Aβ42/40 ratio (p-values<0.004). SCD was not associated with tau, p-tau, or NfL levels ( p- values>0.38). SCD score interacted with sex on Aβ42/40 ratio ( p =0.03) but no other biomarkers ( p -values>0.10). In stratified models, higher SCD was associated with lower Aβ42/40 ratio in men ( p =0.0003) but not in women ( p =0.48). SCD score interacted with education on Aβ42 ( p =0.005) and Aβ42/40 ratio ( p =0.001) such that higher education was associated with a stronger negative association between SCD and amyloid levels. No SCD score x reading level interaction was found (p-values> 0.51) though significant associations between SCD and amyloid markers were seen in the higher reading level group (p-values<0.004) but not the lower reading level group (p-values>0.12) when stratified by a median split in reading level.

Conclusion

Among community-dwelling older adults free of clinical dementia, higher SCD was associated with greater cerebral amyloid accumulation, one of the earliest pathological AD changes. SCD appears most useful in detecting early AD-related brain changes in men and individuals with higher quantity and quality of education. SCD was not associated with CSF markers of tau pathology or neurodegeneration. These findings suggest that considering sex and education is important when assessing SCD in older adults.

Prevalence and risk factors for subjective cognitive decline and the correlation with objective cognition among community-dwelling older adults in China: Results from the Hubei memory and aging cohort study

INTRODUCTION

The prevalence and risk factors for subjective cognitive decline (SCD) and its correlation with objective cognition decline (OCD) among community-dwelling older adults is inconsistent.

METHODS

Older adults underwent neuropsychological and clinical evaluations to reach a consensus on diagnoses.

RESULTS

This study included 7486 adults without mild cognitive impairment and dementia (mean age: 71.35 years [standard deviation = 5.40]). The sex-, age-, and residence-adjusted SCD prevalence was 58.33% overall (95% confidence interval: 58.29% to 58.37%), with higher rates of 61.25% and 59.87% in rural and female subgroups, respectively. SCD global and OCD language, SCD memory and OCD global, SCD and OCD memory, and SCD and OCD language were negatively correlated in fully adjusted models. Seven health and lifestyle factors were associated with an increased risk for SCD.

DISCUSSION

SCD affected 58.33% of older adults and may indicate concurrent OCD, which should prompt the initiation of preventative intervention for dementia.

HIGHLIGHTS

SCD affects 58.33% of older adults in China. SCD may indicate concurrent objective cognitive decline. Difficulty finding words and memory impairments may indicate a risk for AD. The presence of SCD may prompt preventative treatment initiation of MCI or dementia. Social network factors may be initial targets for the early prevention of SCD.

The Use of Executive Fluency Tasks to Detect Cognitive Impairment in Individuals with Subjective Cognitive Decline

OBJECTIVE

Although evidence has indicated that subjective cognitive decline (SCD) may be an early sign of Alzheimer's disease (AD), the objectification of cognitive impairment in SCD is challenging, mainly due to the lack of sensitivity in assessment tools. The present study investigated the potential contribution of two verbal fluency tasks with high executive processing loads to the identification of cognitive impairment in SCD.

METHODS

A total of 60 adults with SCD and 60 healthy controls (HCs) performed one free action (verb) fluency task and two fluency tasks with more executive processing load-an alternating fluency task and an orthographic constraint fluency task-and the results were compared.

RESULT

In the free action fluency task, the performance of the participants with SCD and the HCs was similar. However, HCs performed significantly better than SCD in the alternating fluency task, which required mental flexibility, and the orthographic constraint fluency task, which required inhibition.

DISCUSSION

The study findings suggest that verbal fluency tasks with high executive processing load could be useful in detecting cognitive deficits at the preclinical stage of AD. The inclusion of such tests in assessment batteries should be considered in order to improve the detection of subtle cognitive impairment in preclinical major neurocognitive disorder populations.

Longitudinal Trajectories of Participant- and Study Partner-Rated Cognitive Decline, in Relation to Alzheimer's Disease Biomarkers and Mood Symptoms

Whereas discrepancies between participant- and study partner-reported cognitive concerns on the Alzheimer's disease (AD) continuum have been observed, more needs to be known regarding the longitudinal trajectories of participant- vs. study partner-reported concerns, particularly their relationship to AD biomarkers and mood symptomology. Additionally, it is unclear whether years of in-clinic data collection are needed to observe relationships with AD biomarkers, or whether more frequent, remote assessments over shorter periods of time would suffice. This study primarily sought to examine the relationships between longitudinal trajectories of participant- and study partner-rated cognitive decline and baseline biomarker levels [i.e., amyloid and tau positron emission tomography (PET)], in addition to how mood symptomatology may alter these trajectories of concerns over a 2-year period. Baseline mood was associated with longitudinal participant-rated concerns, such that participants with elevated depression and anxiety scores at baseline had decreasing concerns about cognitive decline over time (fixed estimate = -0.17, 95% CI [-0.29 to -0.05], t = -2.75, df = 457, adj. p = 0.012). A significant interaction between baseline amyloid (fixed estimate = 4.07, 95% CI [1.13-7.01], t = 2.72, df = 353, adj. p = 0.026) and tau (fixed estimate = 3.50, 95% CI [0.95-6.06], t = 2.70, df = 331, adj. p = 0.030) levels was associated with increasing study partner concerns, but not participant concerns, over time. The interaction between amyloid and study partner concerns remained significant when utilizing only the first year of concern-related data collection. Overall, these results suggest that frequent, remote assessment of study partner-reported concerns may offer additional insight into the AD clinical spectrum, as study partners appear to more accurately update their concerns over time with regard to pathology, with these concerns less influenced by participants' mood symptomatology.

Tau Biomarkers in Dementia: Positron Emission Tomography Radiopharmaceuticals in Tauopathy Assessment and Future Perspective

Abnormal accumulation of Tau protein is closely associated with neurodegeneration and cognitive impairment and it is a biomarker of neurodegeneration in the dementia field, especially in Alzheimer’s disease (AD); therefore, it is crucial to be able to assess the Tau deposits in vivo. Beyond the fluid biomarkers of tauopathy described in this review in relationship with the brain glucose metabolic patterns, this review aims to focus on tauopathy assessment by using Tau PET imaging. In recent years, several first-generation Tau PET tracers have been developed and applied in the dementia field. Common limitations of first-generation tracers include off-target binding and subcortical white-matter uptake; therefore, several institutions are working on developing second-generation Tau tracers. The increasing knowledge about the distribution of first- and second-generation Tau PET tracers in the brain may support physicians with Tau PET data interpretation, both in the research and in the clinical field, but an updated description of differences in distribution patterns among different Tau tracers, and in different clinical conditions, has not been reported yet. We provide an overview of first- and second-generation tracers used in ongoing clinical trials, also describing the differences and the properties of novel tracers, with a special focus on the distribution patterns of different Tau tracers. We also describe the distribution patterns of Tau tracers in AD, in atypical AD, and further neurodegenerative diseases in the dementia field.

Optimizing Subjective Cognitive Decline to Detect Early Cognitive Dysfunction

BACKGROUND

The utility of subjective cognitive decline (SCD) as an indicator of preclinical AD is overshadowed by its inconsistent association with objective cognition.

OBJECTIVE

This study examines if manipulations of SCD measurement affect its association with early cognitive dysfunction characteristic of preclinical AD.

METHODS

Cognitively healthy older adults (n = 110) completed SCD questionnaires that elicited complaints in general, compared to 5 years ago (retrospective SCD) and compared to their peers (age-anchored SCD) in binary and Likert scales. Outcome cognitive tasks included an associative memory task (Face-Name Test), a visual short-term memory binding task (STMB test), and a clinical neuropsychological list learning test (Selective Reminder Test).

RESULTS

SCD complaints, when compared to age-matched peers (age-anchored SCD) were endorsed less frequently than complaints compared to 5 years ago (retrospective SCD) (p < 0.01). In demographically adjusted regressions, age-anchored ordinal-rated SCD was associated with short term memory binding (β= -0.22, p = 0.040, CI = -0.45, -0.01), associative memory (β= -0.26, p = 0.018, CI = -0.45, -0.06), and list learning (β= -0.31, p = 0.002, CI = -0.51, -0.12). Retrospective and general ordinal-rated SCD was associated with associative memory (β= -0.25, p = 0.012, CI = -0.44, -0.06; β= -0.29, p = 0.003, CI = -0.47, -0.10) and list learning only (β= -0.25, p = 0.014, CI = -0.45, -0.05; β= -0.28, p = 0.004, CI = -0.48, -0.09).

CONCLUSION

Ordinal age-anchored SCD appears better suited than other SCD measurements to detect early cognitive dysfunction characteristic of preclinical AD.

The relationship between white matter microstructure and self-perceived cognitive decline

Subjective cognitive decline (SCD) is a perceived cognitive change prior to objective cognitive deficits, and although it is associated with Alzheimer's disease (AD) pathology, it likely results from multiple underlying pathologies. We investigated the association of white matter microstructure to SCD as a sensitive and early marker of cognitive decline and quantified the contribution of white matter microstructure separate from amyloidosis. Vanderbilt Memory & Aging Project participants with diffusion MRI data and a 45-item measure of SCD were included [n = 236, 137 cognitively unimpaired (CU), 99 with mild cognitive impairment (MCI), 73 ± 7 years, 37% female]. A subset of participants (64 CU, 40 MCI) underwent a fasting lumbar puncture for quantification of cerebrospinal fluid (CSF) amyloid-β(CSF Aβ₄₂), total tau (CSF t-tau), and phosphorylated tau (CSF p-tau). Diffusion MRI data was post-processed using the free-water (FW) elimination technique, which allowed quantification of extracellular (FW) and intracellular compartment (fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity) microstructure. Microstructural values were quantified within 11 cognitive-related white matter tracts, including medial temporal lobe, frontal transcallosal, and fronto-parietal tracts using a region of interest approach. General linear modeling related each tract to SCD scores adjusting for age, sex, race/ethnicity, education, Framingham Stroke Risk Profile scores, APOE ε4 carrier status, diagnosis, Geriatric Depression Scale scores, hippocampal volume, and total white matter volume. Competitive models were analyzed to determine if white matter microstructural values have a unique role in SCD scores separate from CSF Aβ₄₂. FW-corrected radial diffusivity (RD_T) was related to SCD scores in 8 tracts: cingulum bundle, inferior longitudinal fasciculus, as well as inferior frontal gyrus (IFG) pars opercularis, IFG orbitalis, IFG pars triangularis, tapetum, medial frontal gyrus, and middle frontal gyrus transcallosal tracts. While CSF Aβ₄₂ was related to SCD scores in our cohort (R_adj² = 39.03%; β = -0.231; p = 0.020), competitive models revealed that fornix and IFG pars triangularis transcallosal tract RD_T contributed unique variance to SCD scores beyond CSF Aβ₄₂ (R_adj² = 44.35% and R_adj² = 43.09%, respectively), with several other tract measures demonstrating nominal significance. All tracts which demonstrated nominal significance (in addition to covariates) were input into a backwards stepwise regression analysis. ILF RD_T, fornix RD_T, and UF FW were best associated with SCD scores (R_adj² = 46.69%; p = 6.37 × 10^-12). Ultimately, we found that medial temporal lobe and frontal transcallosal tract microstructure is an important driver of SCD scores independent of early amyloid deposition. Our results highlight the potential importance of abnormal white matter diffusivity as an early contributor to cognitive decline. These results also highlight the value of incorporating multiple biomarkers to help disentangle the mechanistic heterogeneity of SCD as an early stage of cognitive decline.

Awareness of Cognitive Decline in Patients With Alzheimer's Disease: A Systematic Review and Meta-Analysis

Background: Identifying a poor degree of awareness of cognitive decline (ACD) could represent an early indicator of Alzheimer's disease (AD). Objectives: (1) to understand whether there is evidence of poor ACD in the pre-dementia stages of AD; (2) to summarize the main findings obtained investigating ACD in AD; (3) to propose a conceptual framework. Data Sources: We searched Scopus, Pubmed, and the reference lists for studies published up to August 2020. Original research articles must report a measure of ACD and included individuals with AD dementia, or prodromal AD (or MCI), or being at risk for AD. Data Synthesis: All studies covering preclinical, prodromal, and AD dementia were systematically reviewed. We intended to perform a meta-analysis of empirical studies on preclinical AD or prodromal AD (or MCI), to compare ACD between clinical groups. Due to the paucity of literature on preclinical AD, meta-analysis was only possible for prodromal AD (or MCI) studies. Results: We systematically reviewed 283 articles, and conducted a meta-analysis of 18 articles on prodromal AD (or MCI), showing that ACD was not significantly different between patients with amnestic and non-amnestic MCI (SMD = 0.09, p = 0.574); ACD was significantly poorer in amnestic MCI (SMD = -0.56, p = 0.001) and mild AD (SMD = -1.39, p < 0.001) than in controls; ACD was also significantly poorer in mild AD than in amnestic MCI (SMD = -0.75, p < 0.001), as well as poorer than in non-amnestic MCI (SMD = -1.00, p < 0.001). We also discuss key findings on ACD in AD, such as its neural and cognitive correlates. Conclusions and Implications: We propose that patients may be complaining of their initial subtle cognitive changes, but ACD would soon start to decrease. The individual would show mild anosognosia in the MCI stage, and severe anosognosia in dementia. The evaluation of ACD (comparing self-report to cognitive scores or to informant-report) could be useful to guide the clinician toward a timely diagnosis, and in trials targeting early-stage AD.

Social Networks and Cerebrospinal Fluid Biomarkers of Alzheimer's Disease Pathology in Cognitively Intact Older Adults: The CABLE Study

BACKGROUND

Although social networks are deemed as moderators of incident Alzheimer's disease (AD), few data are available on the mechanism relevant to AD pathology.

OBJECTIVE

We aimed to investigate whether social networks affect metabolism of cerebrospinal fluid (CSF) AD biomarkers during early stage and identify modification effects of genetic factor and subjective cognitive decline (SCD).

METHODS

We studied participants from the Chinese Alzheimer's disease Biomarker and Lifestyle (CABLE) database who received cognition assessments and CSF amyloid-β (Aβ1-42 and Aβ1-40) and tau proteins (total-tau [T-tau] and phosphorylated-tau [P-tau]) measurements. The social networks were measured using self-reported questionnaires about social ties. Linear regression models were used.

RESULTS

Data were analyzed from 886 cognitively intact individuals aged 61.91 years (SD = 10.51), including 295 preclinical AD participants and 591 healthy controls. Social networks were mostly associated with CSF indicators of AD multi-pathologies (low P-tau/Aβ1-42 and T-tau/Aβ1-42 and high Aβ1-42/Aβ1-40). Significant differences of genetic and cognitive status were observed for CSF indicators, in which associations of social network scores with CSF P-tau and indicators of multi-pathologies appeared stronger in APOE 4 carriers (versus non-carriers) and participants with SCD (versus controls), respectively. Alternatively, more pronounced associations for CSF T-tau (β= -0.005, p < 0.001), Aβ1-42/Aβ1-40 (β= 0.481, p = 0.001), and T-tau/Aβ1-42 (β= -0.047, p < 0.001) were noted in preclinical AD stage than controls.

CONCLUSION

These findings consolidated strong links between social networks and AD risks. Social networks as a modifiable lifestyle probably affected metabolisms of multiple AD pathologies, especially among at-risk populations.

Prediction of 7-year's conversion from subjective cognitive decline to mild cognitive impairment

Subjective cognitive decline (SCD) is a high‐risk yet less understood status before developing Alzheimer's disease (AD). This work included 76 SCD individuals with two (baseline and 7 years later) neuropsychological evaluations and a baseline T1‐weighted structural MRI. A machine learning‐based model was trained based on 198 baseline neuroimaging (morphometric) features and a battery of 25 clinical measurements to discriminate 24 progressive SCDs who converted to mild cognitive impairment (MCI) at follow‐up from 52 stable SCDs. The SCD progression was satisfactorily predicted with the combined features. A history of stroke, a low education level, a low baseline MoCA score, a shrunk left amygdala, and enlarged white matter at the banks of the right superior temporal sulcus were found to favor the progression. This is to date the largest retrospective study of SCD‐to‐MCI conversion with the longest follow‐up, suggesting predictable far‐future cognitive decline for the risky populations with baseline measures only. These findings provide valuable knowledge to the future neuropathological studies of AD in its prodromal phase.

Subjective Cognitive Decline, Cognitive Reserve Indicators, and the Incidence of Dementia

OBJECTIVE

Both cognitive reserve and subjective cognitive decline are closely related to the risk of dementia. We investigated whether cognitive reserve can modify the risk of dementia developing from subjective cognitive decline.

DESIGN

Longitudinal population-based study.

SETTING AND PARTICIPANTS

The prospective study analyzed data from 2099 participants aged 65 or over from the Cognitive Function and Ageing Study-Wales (CFAS-Wales).

METHODS

Dementia was ascertained through the comprehensive judgment symptoms of geriatric mental state automated geriatric examination for computer assisted taxonomy (GMS-AGECAT). Subjective cognitive decline was evaluated by 2 questions in the baseline interview. Cognitive reserve indicators were derived from 3 previously identified factors: early life education, mid-life occupational complexity, and late-life cognitive activities. We used logistic regression models to estimate dementia risk in relation to subjective cognitive decline and indicators of cognitive reserve. The interaction between subjective cognitive decline and cognitive reserve were evaluated by additive and multiplicative scales.

RESULTS

Baseline subjective cognitive decline and low cognitive reserve significantly increased the risk of dementia, after 2 years of follow-up. There was an additive interaction between subjective cognitive decline and cognitive reserve [the relative excess risk due to interaction = -0.63, 95% confidence interval (CI) = -0.89 to -0.36, P for additive interaction <0.001]. There was no multiplicative interaction between subjective cognitive decline and cognitive reserve indicator (P = .138). Statistically significant association between subjective cognitive decline and dementia was found only in the low-level and medium-level cognitive reserve group (OR = 3.78, 95% CI = 1.50-9.55 and OR = 3.64, 95% CI = 1.09-12.2, respectively), but not in the high-level groups.

CONCLUSION AND IMPLICATIONS

Cognitive reserve attenuated subjective cognitive decline associated risk of developing dementia. This finding suggests the need for greater emphasis on detecting prodromal dementia when older patients having lower cognitive reserve present with subjective cognitive decline.

Subjective cognitive decline and subsequent dementia: a nationwide cohort study of 579,710 people aged 66 years in South Korea

Background

Subjective cognitive decline (SCD) is a potential risk factor for dementia. We aimed to investigate the association between SCD and subsequent dementia in a nationwide population-based cohort in South Korea.

Methods

This cohort included 579,710 66-year-old adults who were followed for a total of 3,870,293 person-years (average 6.68 ± 1.33 years per person). All subjects completed a questionnaire about subjective memory impairment, the Pre-screening Korean Dementia Screening Questionnaire (KDSQ-P), which included a validated 5-item derivative, and were determined to have SCD based on a single question assessing memory decline. Depressive symptoms were assessed in all subjects using a 3-item modified geriatric depression scale. Hazard ratios were estimated using the Cox proportional hazards model and compared between subjects with and without SCD.

Results

Compared to subjects without SCD, those with SCD were more likely to develop dementia (incidence per 1000 person-years: non-SCD, 5.66; SCD, 8.59). After adjusting for potential confounding factors, the risk of subsequent dementia significantly increased in subjects with SCD, with an adjusted hazard ratio (aHR) of 1.38 (95% confidence interval [CI] 1.34 to 1.41). The risk of subsequent dementia was greatly increased in subjects with higher KDSQ-P scores (aHR = 2.77, 95% CI 2.35 to 3.27). A significant association between SCD and dementia was observed in both depressive and non-depressive symptom groups (aHR = 1.50, 95% CI 1.42 to 1.57 in subjects with depressive symptoms; aHR = 1.33, 95% CI 1.29 to 1.37 in subjects without depressive symptoms; P = 0.001).

Conclusions

In this population of 66-year-old individuals, SCD was significantly associated with an increased risk of subsequent dementia. This association was found in both depressive and non-depressive groups, with an increased risk of dementia in the presence of depressive symptoms. Our findings suggest that SCD indicates a risk for dementia. Further studies are needed to delineate potential approaches to preventing the development of dementia in individuals with SCD.

Prevalence of Cognitive Frailty Phenotypes and Associated Factors in a Community-Dwelling Elderly Population

OBJECTIVES

Cognitive frailty was notable target for the prevention of adverse health outcomes in future. The goal of this study was to use a population-based survey to investigate cognitive frailty phenotypes and potentially sociodemographic factors in elderly Chinese individuals.

DESIGN

Cross-sectional study.

SETTING

General community.

PARTICIPANTS

A total of 5328 elderly adults (aged 60 years or older, mean age 71.36 years) enrolled in the Shanghai study of health promotion for elderly individuals with frailty.

MEASUREMENTS

The 5-item FRAIL scale and the 3-item Rapid Cognitive Screen tools were used to assess physical frailty and cognitive impairment, including dementia or mild cognitive impairment (MCI). Physical frailty was diagnosed by limitations in 3 or more of the FRAIL scale domains and pre-physical frailty by 1-2 limitations. Subjective cognitive decline (SCD) and pre-MCI SCD, was diagnosed with two self-report measures based on memory and other cognitive domains in elderly adults.

RESULTS

Of the participating individuals, 97.17% (n= 5177, female 53.4%) were eligible. Notably, 9.67%, 41.61% and 35.20% of participants were MCI, SCD and pre-MCI SCD; 35.86% and 4.41% exhibited physical pre-frailty and frailty; and 19.86% and 6.30% exhibited reversible and potential reversible cognitive frailty. Logistic regression analyses indicated that physical frailty phenotypes were significantly associated with MCI with SCD, and pre-MCI with SCD. Older single females with a high education level were more likely to exhibit the reversible cognitive frailty; and younger elderly individuals with a middle education level were at lower risk for potentially reversible cognitive frailty.

CONCLUSIONS

The prevalence of pre-physical and reversible cognitive frailty was high in elderly individuals and age was the most significant risk factor for all types of frailty phenotypes. To promote the rapid screening protocol of cognitive frailty in community-dwelling elderly is important to find high-risk population, implement effective intervention, and decrease adverse prognosis.

Association of Subjective Memory Complaints with the Left Parahippocampal Amyloid Burden in Mild Cognitive Impairment

BACKGROUND

Subjective memory complaints (SMC) are a risk factor for Alzheimer's disease.

OBJECTIVE

We aimed to explore the association between SMC and regional amyloid-β (Aβ) deposition in mild cognitive impairment (MCI).

METHODS

Sixty-eight individuals with MCI were recruited. [18F]Florbetaben PET scans were performed. T1-weighted 3D volumes were also acquired for co-registration with PET and for defining the regions of interest (ROI). Two step exploratory partial correlation analyses between SMC and Aβ deposition were performed with covariates of age, sex, education, and depression. Furthermore, for the priori ROI that had the most significant partial correlation, we investigated the correlation between the SMC and regional Aβ burden using a multiple linear regression model controlling for depression, age, sex, and education.

RESULTS

Significant positive correlations between the SMC and Aβ burden was found in the medial temporal ROI (first step) and in the left parahippocampus ROI (second step). In the priori left parahippocampus, we found significant correlation between the SMC and Aβ burden (R2 = 0.473, p = 0.014).

CONCLUSIONS

Our study suggested that the SMC was associated with amyloid accumulation, especially in the left parahippocampus, in individuals with MCI.

Cognitive Complaints in Memory Clinic Patients and in Depressive Patients: An Interpretative Phenomenological Analysis

BACKGROUND AND OBJECTIVES

Cognitive complaints are discussed as early signs of Alzheimer's disease (AD). However, they are also very common in cognitively normal older adults and in patients with depression. Qualitative, interview-based approaches might be useful to identify those features of cognitive complaints specific for the experiences of cognitive decline in preclinical or prodromal AD versus those complaints typically reported by depressed patients.

RESEARCH DESIGN AND METHODS

A semi-structured interview was administered to 21 cognitively normal older adults (HC), 18 nondemented memory clinic patients (MC), and 11 patients with a major depression (MD), all above 55 years. Interpretative phenomenological analysis (IPA) was applied to the interview transcripts to develop emerging complaint themes in each group. To identify thematic correspondence and possibly novel, hitherto unappreciated themes, the extracted complaint categories were compared with the neurocognitive domains in the DSM-5 and the content of the Everyday Cognition questionnaire (E-Cog).

RESULTS

IPA yielded 18 cognitive complaint categories in MC, 10 in depressive patients, and 10 categories in the HC group. Several themes were common across groups, but some were group-specific, for example, spatial disorientation was only reported in MC patients. Some of these MC-specific themes were neither represented by DSM-5 domains nor by the E-Cog.

DISCUSSION AND IMPLICATIONS

We report a comprehensive qualitative description of cognitive complaints in old age which could help to develop questionnaires or structured interviews to better assess AD-related subjective cognitive decline. This may help to increase specificity in selecting high-risk subjects in research settings and improve clinical judgment of diverse cognitive complaints types mentioned by their patients.

Which features of subjective cognitive decline are related to amyloid pathology? Findings from the DELCODE study

Background

Subjective cognitive decline (SCD) has been proposed as a pre-MCI at-risk condition of Alzheimer’s disease (AD). Current research is focusing on a refined assessment of specific SCD features associated with increased risk for AD, as proposed in the SCD-plus criteria. We developed a structured interview (SCD-I) for the assessment of these features and tested their relationship with AD biomarkers.

Methods

We analyzed data of 205 cognitively normal participants of the DELCODE study (mean age = 68.9 years; 52% female) with available CSF AD biomarkers (Aß-42, p-Tau181, Aß-42/Tau ratio, total Tau). For each of five cognitive domains (including memory, language, attention, planning, others), a study physician asked participants about the following SCD-plus features: the presence of subjective decline, associated worries, onset of SCD, feeling of worse performance than others of the same age group, and informant confirmation. We compared AD biomarkers of subjects endorsing each of these questions with those who did not, controlling for age. SCD was also quantified by two summary scores: the number of fulfilled SCD-plus features, and the number of domains with experienced decline. Covariate-adjusted linear regression analyses were used to test whether these SCD scores predicted abnormality in AD biomarkers.

Results

Lower Aß-42 levels were associated with a reported decline in memory and language abilities, and with the following SCD-plus features: onset of subjective decline within 5 years, confirmation of cognitive decline by an informant, and decline-related worries. Furthermore, both quantitative SCD scores were associated with lower Aß42 and lower Aß42/Tau ratio, but not with total Tau or p-Tau181.

Conclusions

Findings support the usefulness of a criterion-based interview approach to assess and quantify SCD in the context of AD and validate the current SCD-plus features as predictors of AD pathology. While some features seem to be more closely associated with AD biomarkers than others, aggregated scores over several SCD-plus features or SCD domains may be the best predictors of AD pathology.

Electronic supplementary material

The online version of this article (10.1186/s13195-019-0515-y) contains supplementary material, which is available to authorized users.

A Link between Subjective Perceptions of Memory and Physical Function: Implications for Subjective Cognitive Decline

Subjective impairment in memory is a frequently defining feature of subjective cognitive decline (SCD), a state hypothesized to precede objectively apparent cognitive symptoms of Alzheimer's disease (AD) and to hold promise as a non-invasive, inexpensive, preclinical indicator of AD. However, a full model of the factors that contribute to subjective memory (SM), and therefore to SCD, has yet to be articulated. While SM impairment is widely known to be associated with negative affect, the extent to which SM functioning may also reflect other factors, particularly subjective beliefs or perceptions about one's health, is not known. To examine the extent to which SM is associated with subjective perceptions of health more broadly, the current study investigated the link between SM and subjective physical functioning (independent of depressive affect, and objective cognitive and physical function) in an ethnically diverse sample of 471 older adults enrolled in the population-based Northern Manhattan Aging Project. 199 (42%) participants endorsed no difficulty on a 5-point SM index while 272 (58%) endorsed some degree of difficulty. As hypothesized, SM correlated with both depression and subjective physical function, but not with age, education, global cognition, or objective physical function. When objective and subjective physical function were entered in two separate, adjusted linear regressions predicting SM, only subjective physical function and depressive affect independently predicted SM. Subjective perceptions of memory appear to reflect individuals' broader health perceptions in part. Articulating the various correlates of SM will improve identification of SCD specific to preclinical AD.

Subjective cognitive decline: preclinical manifestation of Alzheimer's disease

Subjective cognitive decline (SCD), characterized by a very early and subtle cognitive decline prior to the appearance of objective cognitive impairment, is considered to be the preclinical manifestation of Alzheimer's disease (AD). Given the lack of significant abnormalities in standardized neuropsychological assessments for individuals with SCD, biochemical and neuroimaging biomarkers may be important indicators of the preclinical stage of AD. The application of various biomarkers derived from the cerebrospinal fluid and neuroimaging thus has the potential to make AD-related pathology detectable in vivo. In this review, we discuss the conceptual evolution of SCD as an entity and further elucidate characteristic cerebrospinal fluid and neuroimaging biomarkers of SCD.

Cerebrospinal fluid and blood biomarkers for neurodegenerative dementias: An update of the Consensus of the Task Force on Biological Markers in Psychiatry of the World Federation of Societies of Biological Psychiatry

In the 12 years since the publication of the first Consensus Paper of the WFSBP on biomarkers of neurodegenerative dementias, enormous advancement has taken place in the field, and the Task Force takes now the opportunity to extend and update the original paper. New concepts of Alzheimer's disease (AD) and the conceptual interactions between AD and dementia due to AD were developed, resulting in two sets for diagnostic/research criteria. Procedures for pre-analytical sample handling, biobanking, analyses and post-analytical interpretation of the results were intensively studied and optimised. A global quality control project was introduced to evaluate and monitor the inter-centre variability in measurements with the goal of harmonisation of results. Contexts of use and how to approach candidate biomarkers in biological specimens other than cerebrospinal fluid (CSF), e.g. blood, were precisely defined. Important development was achieved in neuroimaging techniques, including studies comparing amyloid-β positron emission tomography results to fluid-based modalities. Similarly, development in research laboratory technologies, such as ultra-sensitive methods, raises our hopes to further improve analytical and diagnostic accuracy of classic and novel candidate biomarkers. Synergistically, advancement in clinical trials of anti-dementia therapies energises and motivates the efforts to find and optimise the most reliable early diagnostic modalities. Finally, the first studies were published addressing the potential of cost-effectiveness of the biomarkers-based diagnosis of neurodegenerative disorders.

Different Cognitive Complaint Profiles in Memory Clinic and Depressive Patients

OBJECTIVE

Cognitive complaints are considered early indicators of incipient Alzheimer's disease (AD) but are very common in geriatric patients, especially in patients with major depressive disorder (MDD). The clinical assessment of cognitive complaints is still poorly operationalized. Recent qualitative research suggests that certain phenomenologic complaint themes may have some specificity for prodromal AD. The aim of the study was to replicate and explore their occurrence in a clinical setting.

METHODS

In a cross-sectional, case-control study using a mixed-methods approach, 23 memory clinic (cognitive complainers [CC]) patients, 21 psychiatric inpatients with MDD, and 21 healthy control subjects, aged 55-86 years, were assessed at the Department of Psychiatry and Psychotherapy and German Center for Neurodegenerative Diseases, Bonn. A newly developed semistructured interview addressing 12 complaint themes was used, and transcribed open format responses were coded by qualitative expert rating (theme absent versus present) and compared between the groups.

RESULTS

Seven complaint themes (e.g., sense of predomination, progression) were significantly more often endorsed by the CC group, together with a novel theme of "distractible speech." Complaint themes in those with depression aligned with the depressive symptoms and appeared to be partly different from the complaint pattern of the CC group.

CONCLUSION

Previously established themes were found to be feasible for conversion into a semistructured interview. Several complaint phenotypes were confirmed and previous themes significantly expanded by providing first evidence for a qualitatively different complaint profile in MDD compared with CC. Future investigations may benefit from better characterizing the phenomenologic and qualitative characteristics of AD-related complaints.

Criterion-related validity of self-reported stair climbing in older adults

INTRODUCTION

Stair climbing is an activity of daily living that might contribute to increase levels of physical activity (PA). To date, there is no study examining the validity of climbing stairs assessed by self-report. The aim of this study was, therefore, to examine the validity of estimated stair climbing from one question included in a common questionnaire compared to a pattern-recognition activity monitor in older adults.

METHODS

A total of 138 older adults (94 women), aged 65-86 years (70.9 ± 4.7 years), from the IMPACT65 + study participated in this validity study. Estimates of stair climbing were obtained from the European Prospective Investigation into Cancer and Nutrition (EPIC) PA questionnaire. An objective assessment of stair climbing was obtained with the Intelligent Device for Energy Expenditure and Activity (IDEEA) monitor.

RESULTS

The correlation between both methods to assess stair climbing was fair (ρ = 0.22, p = 0.008 for PA energy expenditure and ρ = 0.26, p = 0.002 for duration). Mean differences between self-report and the IDEEA were 7.96 ± 10.52 vs. 9.88 ± 3.32 METs-min/day for PA energy expenditure, and 0.99 ± 1.32 vs. 1.79 ± 2.02 min/day for duration (both Wilcoxon test p < 0.001). Results from the Bland-Altman analysis indicate that bias between both instruments were -1.91 ± 10.30 METs-min/day and -0.80 ± 1.99 min/day, and corresponding limits of agreement for the two instruments were from 18.27 to -22.10 METs-min/day and from 3.09 to -4.70 min/day, respectively.

CONCLUSION

Our results indicate that self-reported stair climbing has modest validity to accurately rank old age participants, and underestimates both PAEE and its duration, as compared with an objectively measured method.

Tau in Late-Life Depression: A Systematic Review and Meta-Analysis

A lifetime history of major depressive disorder (MDD) increases the risk of developing Alzheimer's disease, of which neurofibrillary tangles due to abnormal tau proteins are a hallmark. We systematically reviewed the literature on tau in MDD and identified 49 relevant articles spanning a number of modalities, including cerebrospinal fluid (CSF) analysis, positron emission tomography, and clinicopathological correlation. We compared CSF total and phosphorylated tau proteins in MDD and controls using a meta-analytic approach. We found no difference in total or phosphorylated tau in MDD. We also found no difference in a comparison of a subgroup excluding studies with significant age differences. Positron emission tomography studies lacked specificity. Clinicopathological studies failed to associate neurofibrillary tangles with MDD. The available data on tau in MDD is limited. The involvement of tau in a subset of MDD cannot be ruled out and requires prospective exploration.

Asymmetry of Hippocampus and Amygdala Defect in Subjective Cognitive Decline Among the Community Dwelling Chinese

Background: Subjective cognitive decline (SCD) may be the first clinical sign of Alzheimer's disease (AD). SCD individuals with normal cognition may already have significant medial temporal lobe atrophy. However, few studies have been devoted to exploring the alteration of left-right asymmetry with hippocampus and amygdala in SCD. The aim of this study was to compare SCD individuals with amnestic mild cognitive impairment (MCI) patients and the normal population for volume and asymmetry of hippocampus, amygdala and temporal horn, and to assess their relationship with cognitive function in elderly population living in China. Methods: 111 SCD, 30 MCI, and 67 healthy controls (HC) underwent a standard T1-weighted MRI, from which the volumes of the hippocampus and amygdala were calculated and compared. Then we evaluated the pattern and extent of asymmetry in hippocampus and amygdala of these samples. Furthermore, we also investigated the relationship between the altered brain regions and cognitive function. Results: Among the three groups, SCD showed more depressive symptoms (p < 0.001) and higher percentage of heart disease (16.4% vs. 35.1%, p = 0.007) than controls. In terms of brain data, significant differences were found in the volume and asymmetry of both hippocampus and amygdala among the three groups (P < 0.05). In logistic analysis controlled by age, gender, education level, depression symptoms, anxiety symptom, somatic disease and lifestyle in terms of smoking, both SCD and MCI individuals showed significant decreased right hippocampal and amygdala volume than controls. For asymmetry pattern, a ladder-shaped difference of left-larger-than-right asymmetry was found in amygdala with MCI>SCD>HC, and an opposite asymmetry of left-less-than-right pattern was found with HC>SCD>MCI in hippocampus. Furthermore, correlation was shown between the volume of right hippocampus and right amygdala with MMSE and MoCA in SCD group. Conclusion: Our results supported that SCD individuals are biologically distinguishable from HC, and this may relate to cognitive impairment, although more longitudinal studies are need to investigate this further.Moreover, different levels of asymmetry in hippocampus and amygdala might be a potential dividing factor to differentiate clinical diagnosis.

Region-Specific Association of Subjective Cognitive Decline With Tauopathy Independent of Global β-Amyloid Burden

Importance

The ability to explore associations between reports of subjective cognitive decline (SCD) and biomarkers of early Alzheimer disease (AD) pathophysiologic processes (accumulation of neocortical β-amyloid [Aβ] and tau) provides an important opportunity to understand the basis of SCD and AD risk.

Objective

To examine associations between SCD and global Aβ and tau burdens in regions of interest in clinically healthy older adults.

Design, Setting, and Participants

This imaging substudy of the Harvard Aging Brain Study included 133 clinically healthy older participants (Clinical Dementia Rating Scale global scores of 0) participating in the Harvard Aging Brain Study who underwent cross-sectional flortaucipir F 18 (previously known as AV 1451, T807) positron emission tomography (FTP-PET) imaging for tau and Pittsburgh compound B carbon 11-labeled PET (PiB-PET) imaging for Aβ. The following 2 regions for tau burden were identified: the entorhinal cortex, which exhibits early signs of tauopathy, and the inferior temporal region, which is more closely associated with AD-related pathologic mechanisms. Data were collected from June 11, 2012, through April 7, 2016.

Main Outcomes and Measures

Subjective cognitive decline was measured using a previously published method of z-transforming subscales from the Memory Functioning Questionnaire, the Everyday Cognition battery, and a 7-item questionnaire. The Aβ level was measured according to a summary distribution volume ratio of frontal, lateral temporal and parietal, and retrosplenial PiB-PET tracer uptake. The FTP-PET measures were computed as standardized uptake value ratios. Linear regression models focused on main and interactive effects of Aβ, entorhinal cortical, and inferior temporal tau on SCD, controlling for age, sex, educational attainment, and Geriatric Depression Scale score.

Results

Of the 133 participants, 75 (56.3%) were women and 58 (43.6%) were men; mean (SD) age was 76 (6.9) years (range, 55-90 years). Thirty-nine participants (29.3%) exhibited a high Aβ burden. Greater SCD was associated with increasing entorhinal cortical tau burden (β = 0.35; 95% CI, 0.19-.52; P < .001) and Aβ burden (β = 0.24; 95% CI, 0.08-.40; P = .005), but not inferior temporal tau burden (β = 0.10; 95% CI, -0.08 to 0.28; P = .27). This association between entorhinal cortical tau burden and SCD was largely unchanged after accounting for Aβ burden (β = 0.36; 95% CI, 0.15-.58; P = .001), and no interaction influenced SCD (β = -0.36; 95% CI, -0.34 to 0.09; P = .25). An exploratory post hoc whole-brain analysis also indicated that SCD was predominantly associated with greater tau burden in the entorhinal cortex.

Conclusions and Relevance

Subjective cognitive decline is indicative of accumulation of early tauopathy in the medial temporal lobe, specifically in the entorhinal cortex, and to a lesser extent, elevated global levels of Aβ. Our findings suggest multiple underlying pathways that motivate SCD that do not necessarily interact to influence SCD endorsement. As such, multiple biological factors must be considered when assessing SCD in clinically healthy older adults.

Emerging biomarkers and screening for cognitive frailty

Physical frailty and cognitive frailty are two important targets of secondary intervention in aging research to narrow the gap between life and health span. The objective of the present narrative review was to examine clinical and epidemiological studies investigating the recently proposed construct of cognitive frailty and its subtypes, with a focus on operational definitions, clinical criteria, and emerging biomarkers potentially useful for the screening of this novel entity. Both physical frailty and frailty indexes with a multidimensional nature were associated with late-life cognitive impairment/decline, incident dementia, Alzheimer's disease (AD), mild cognitive impairment, vascular dementia, non-AD dementias, and AD pathology proposing cognitive frailty as a clinical entity with cognitive impairment related to physical causes with a potential reversibility. The new clinical and research AD criteria established by the National Institute on Aging-Alzheimer's Association and the American Psychiatric Association could improve the differential diagnosis of cognitive impairment within the cognitive frailty construct. The emerging biomarkers of sarcopenia, physical frailty, and cognitive impairment will provide the basis to establish more reliable clinical and research criteria for cognitive frailty, using different operational definitions for frailty and cognitive impairment and useful clinical, biological, and imaging markers for this novel clinical construct.

Implementation of subjective cognitive decline criteria in research studies

INTRODUCTION

Subjective cognitive decline (SCD) manifesting before clinical impairment could serve as a target population for early intervention trials in Alzheimer's disease (AD). A working group, the Subjective Cognitive Decline Initiative (SCD-I), published SCD research criteria in the context of preclinical AD. To successfully apply them, a number of issues regarding assessment and implementation of SCD needed to be addressed.

METHODS

Members of the SCD-I met to identify and agree on topics relevant to SCD criteria operationalization in research settings. Initial ideas and recommendations were discussed with other SCD-I working group members and modified accordingly.

RESULTS

Topics included SCD inclusion and exclusion criteria, together with the informant's role in defining SCD presence and the impact of demographic factors.

DISCUSSION

Recommendations for the operationalization of SCD in differing research settings, with the aim of harmonization of SCD measurement across studies are proposed, to enhance comparability and generalizability across studies.

Identifying memory impairment and early dementia in primary care

INTRODUCTION

This study examined the operating characteristics of two-stage case finding to identify memory impairment and very mild dementia.

METHODS

Primary care patients underwent two-stage testing and a subsequent diagnostic assessment to assess outcomes. Patients who screen positive for subjective cognitive decline on the Informant Questionnaire on Cognitive Decline in the Elderly undergo memory testing with the Free and Cued Selective Reminding Test with Immediate Recall. Outcomes were determined without access to these data. A split-half design with discovery and confirmatory samples was used.

RESULTS

One hundred seventeen of 563 (21%) patients had dementia and 68 (12%) had memory impairment but not dementia. Operating characteristics were similar in the discovery and confirmatory samples. In the pooled sample, combined, patients with memory impairment or dementia were identified with good sensitivity (72%) and high specificity (90%). Differences in ethnicity, educational level, or age (≤75, >75) did not affect classification accuracy.

DISCUSSION

Two-stage screening facilitates the efficient identification of older adults with memory impairment or dementia.

The Latent Dementia Phenotype δ is Associated with Cerebrospinal Fluid Biomarkers of Alzheimer's Disease and Predicts Conversion to Dementia in Subjects with Mild Cognitive Impairment

BACKGROUND

The recently proposed latent variable δ is a new tool for dementia case finding. It is built in a structural equation modeling framework of cognitive and functional data and constitutes a novel endophenotype for Alzheimer's disease (AD) research and clinical trials.

OBJECTIVE

To investigate the association of δ with AD biomarkers and to compare the prediction of δ with established scales for conversion to dementia in patients with mild cognitive impairment (MCI).

METHODS

Using data from a multicenter memory clinic study, we examined the external associations of the latent variable δ and compared δ with well-established cognitive and functional scales and cognitive-functional composite scores. For that purpose, logistic regressions with cerebrospinal fluid (CSF) biomarkers and conversion to dementia as dependent variables were performed with the investigated scores. The models were tested for significant differences.

RESULTS

In patients with MCI, δ based on a broad range of cognitive scales (including the ADAS-cog, the MMSE, and the CERAD neuropsychological battery) predicted an abnormal CSF Aβ42/tau ratio indicative of AD (n = 340, AUC = 0.78, p <  0.001), and predicted incident dementia within 1-3 years of follow-up (n = 525, AUC = 0.84, p <  0.001). These associations were generally stronger than for any other scale or cognitive-functional composite examined. Homologs of δ based on reduced test batteries yielded somewhat lower effects.

CONCLUSION

These findings support the interpretation of δ as a construct capturing the disease-related "essence" of cognitive and functional impairments in patients with MCI and dementia, and suggest that δ might become an analytical tool for dementia research.

Subjective cognitive decline: The first clinical manifestation of Alzheimer's disease?

Background

Mild cognitive impairment is considered as the first clinical manifestation of Alzheimer's disease (AD), when the individual exhibits below performance on standardized neuropsychological tests. However, some subjects before having a lower performance on cognitive assessments already have a subjective memory complaint.

Objective

A review about subjective cognitive decline, the association with AD biomarkers and risk of conversion to dementia.

Methods

We performed a comprehensive non-systematic review on PubMed. The keywords used in the search were terms related to subjective cognitive decline.

Results

Subjective cognitive decline is characterized by self-experience of deterioration in cognitive performance not detected objectively through formal neuropsychological testing. However, various terms and definitions have been used in the literature and the lack of a widely accepted concept hampers comparison of studies. Epidemiological data have shown that individuals with subjective cognitive decline are at increased risk of progression to AD dementia. In addition, there is evidence that this group has a higher prevalence of positive biomarkers for amyloidosis and neurodegeneration. However, Alzheimer's disease is not the only cause of subjective cognitive decline and various other conditions can be associated with subjective memory complaints, such as psychiatric disorders or normal aging. The features suggestive of a neurodegenerative disorder are: onset of decline within the last five years, age at onset above 60 years, associated concerns about decline and confirmation by an informant.

Conclusion

These findings support the idea that subjective cognitive complaints may be an early clinical marker that precedes mild cognitive impairment due to Alzheimer's disease.

A Conceptualization of the Utility of Subjective Cognitive Decline in Clinical Trials of Preclinical Alzheimer's Disease

This commentary outlines a conceptual model for subjective cognitive decline (SCD) in relation to Alzheimer's disease (AD) biomarkers in the preclinical stages of disease and a framework for effectively utilizing SCD in secondary prevention clinical trials. Mounting evidence supports the notion that SCD is sensitive to encroaching Aβ-amyloid and neurodegeneration. SCD has also been shown to provide additive information of AD-dementia risk beyond what is known about the biomarker status of the individual. Thus, we provide recommendations for the implementing SCD measurement in clinical trials. We argue that SCD can be measured at three catch points within the course of the clinical trial: firstly, at the initial recruitment and screening phase; secondly, to create more robust estimates of rates of AD-dementia progression; and finally, to measure subjective experiences of cognitive change and quality of life over the course of the trial as a proxy of clinically meaningful functional improvement. We provide recommendations of how SCD can be approached at each of these points. SCD is an important component of the preclinical AD-dementia trajectory. Future studies need to elucidate the interactive influence of Aβ-amyloid and tau on SCD from a spatiotemporal perspective. Even as this evidence accrues, it is clear that SCD can provide unique and additive information about rates of progression and subjectively experienced cognitive change within clinical trials.

Potential fluid biomarkers for pathological brain changes in Alzheimer's disease: Implication for the screening of cognitive frailty

Cognitive frailty (CF) overlaps with early neuropathological alterations associated with aging-related major neurocognitive disorders, including Alzheimer's disease (AD). Fluid biomarkers for these pathological brain alterations allow for early diagnosis in the preclinical stages of AD, and for objective prognostic assessments in clinical intervention trials. These biomarkers may also be helpful in the screening of CF. The present study reviewed the literature and identified systematic reviews of cohort studies and other authoritative reports. The selection criteria for potentially suitable fluid biomarkers included: i) Frequent use in studies of fluid-derived markers and ii) evidence of novel measurement techniques for fluid-derived markers. The present study focused on studies that assessed these biomarkers in AD, mild cognitive impairment and non-AD demented subjects. At present, widely used fluid biomarkers include cerebrospinal fluid (CSF), total tau, phosphorylated tau and amyloid-β levels. With the development of novel measurement techniques and improvements in understanding regarding the mechanisms underlying aging-related major neurocognitive disorders, numerous novel biomarkers associated with various aspects of AD neuropathology are being explored. These include specific measurements of Aβ oligomer or monomer forms, tau proteins in the peripheral plasma and CSF, and novel markers of synaptic dysfunction, neuronal damage and apoptosis, neuronal activity alteration, neuroinflammation, blood brain barrier dysfunction, oxidative stress, metabolites, mitochondrial function and aberrant lipid metabolism. The proposed panels of fluid biomarkers may be useful in the early diagnosis of AD, prediction of the progression of AD from preclinical stages to the dementia stage, and the differentiation of AD from non-AD dementia. In combination with physical frailty, the present study surmised that these biomarkers may also be used as biomarkers for CF, thus contribute to discovering causes and informing interventions for cognitive impairment in individuals with CF.

[Dementia Competence Network. Results and outlook]

BACKGROUND

The Dementia Competence Network (DCN) is represented by academic memory clinics and has three major aims: (1) To facilitate the development of diagnostic tools including neuropsychology, biomarkers, imaging and genetics. (2) To implement clinical trials in mild cognitive impairment and dementia and (3) to improve standard care for dementia in Germany.

AIMS

This article summarizes the achievements of the DCN so far and highlights future perspectives.

METHODS

The DCN has built up two multicentre cohorts. Within the first cohort, patients with mild cognitive impairment or mild dementia were examined longitudinally using multiple neuropsychological assessments and numerous different biomarkers. In a subgroup of the first cohort, patients were treated with antidementive drugs in two placebo-controlled clinical trials. The second cohort included cognitively healthy older people and examined repetitively clinical, neuropsychological and psychosocial parameters for ten years.

RESULTS AND DISCUSSION

The DCN has generated a large data and biomaterial bank. Numerous publications have helped to develop further diagnostic procedures and treatment of cognitive disorders and dementia. The DCN has contributed to end stigmatisation of dementia.