Altered dynamic amplitude of low-frequency fluctuation in individuals at high risk for Alzheimer's disease

The brain's dynamic spontaneous neural activity is significant in supporting cognition; however, how brain dynamics go awry in subjective cognitive decline (SCD) and mild cognitive impairment (MCI) remains unclear. Thus, the current study aimed to investigate the dynamic amplitude of low-frequency fluctuation (dALFF) alterations in patients at high risk for Alzheimer's disease and to explore its correlation with clinical cognitive assessment scales, to identify an early imaging sign for these special populations. A total of 152 participants, including 72 SCD patients, 44 MCI patients and 36 healthy controls (HCs), underwent a resting-state functional magnetic resonance imaging and were assessed with various neuropsychological tests. The dALFF was measured using sliding-window analysis. We employed canonical correlation analysis (CCA) to examine the bi-multivariate correlations between neuropsychological scales and altered dALFF among multiple regions in SCD and MCI patients. Compared to those in the HC group, both the MCI and SCD groups showed higher dALFF values in the right opercular inferior frontal gyrus (voxel P < .001, cluster P < .05, correction). Moreover, the CCA models revealed that behavioural tests relevant to inattention correlated with the dALFF of the right middle frontal gyrus and right opercular inferior frontal gyrus, which are involved in frontoparietal networks (R = .43, P = .024). In conclusion, the brain dynamics of neural activity in frontal areas provide insights into the shared neural basis underlying SCD and MCI.

Investigating the spontaneous brain activities of patients with subjective cognitive decline and mild cognitive impairment: an amplitude of low-frequency fluctuation functional magnetic resonance imaging study

Background

Subjective cognitive decline (SCD) and mild cognitive impairment (MCI) are neurodegenerative processing stages of Alzheimer's disease (AD). Cognitive decline is thought to manifest in intrinsic brain activity changes, but research results yielded conflicting and few studies have explored the roles of brain regions in cognitive decline, and sensitivity of the cognitive field to changes in the altered intrinsic brain activity.

Methods

In this cross-sectional study, 158 elderly participants were recruited from the memory clinic of the First Affiliated Hospital of Nanjing Medical University from July 2019 to May 2021, and grouped into SCD (n=73), MCI (n=46), and normal controls (NC) (n=39). The amplitude of low-frequency fluctuation (ALFF) was calculated and evaluated among the groups. Then canonical correlation analysis (CCA) was conducted to investigate the associations between imaging outcomes and cognitive behaviors.

Results

Neuropsychological tests in different cognitive dimensions and ALFF values of the prefrontal, parietal, and temporal gyrus, were significantly different (P<0.05) among the three groups, with no appreciable decline in daily activity. The changes in intrinsic activities were closely related to the decline in cognitive function (R=0.73, P=0.002). ALFF values in the left middle occipital gyrus, right middle frontal gyrus, left superior frontal gyrus, left angular gyrus, and superior temporal gyrus played significant roles in the analysis, while the Montreal Cognitive Assessment (MoCA) and Auditory-Verbal Learning Test scores were found to be more sensitive to changes in ALFF values.

Conclusions

Spontaneous brain activity is a stable imaging biomarker of cognitive impairment. ALFF changes of the prefrontal, occipital, left angular, and temporal gyrus were sensitive to identifying cognitive decline, and the scores of the Auditory-Verbal Learning Test and MoCA could predict the abnormal intrinsic activities.

Subjective cognitive decline in patients with Parkinson's disease: an updated review

Cognitive impairment in patients with Parkinson's disease (PD) worsens the prognosis of PD and increases caregivers' burden and economic consequences. Recently, subjective cognitive decline (SCD), which refers to self-reported cognitive decline without detectable objective cognitive dysfunction, has been regarded as an at-risk state of mild cognitive impairment (MCI) and a prodromal stage for dementia in Alzheimer's disease (AD). However, studies on PD-SCD have thus far been scarce, and at present there is no consensus regarding the definition of SCD nor a gold standard as an evaluation tool. The present review aimed to look for an association between PD-SCD and objective cognitive function and found that PD with SCD occurred with brain metabolic changes, which were consistent with early aberrant pathological changes in PD. Moreover, PD patients with SCD were likely to progress to future cognitive impairment. It is necessary to establish a guideline for the definition and evaluation of SCD in PD. A larger sample size and more longitudinal investigations are needed to verify the predictive effectiveness of PD-SCD and to detect earlier subtle cognitive decline before MCI.

Relation of modifiable lifestyle and mood factors to cognitive concerns among participants and their study partners in the A4 screen data

Introduction

Subjective cognitive decline (SCD) has been associated with elevated amyloid levels and increased risk of future cognitive decline, as well as modifiable variables, including depression, anxiety, and physical inactivity. Participants generally endorse greater and earlier concerns than their close family and friends (study partners [SPs]), which may reflect subtle changes at the earliest stages of disease among participants with underlying neurodegenerative processes. However, many individuals with subjective concerns are not at risk of Alzheimer's disease (AD) pathology, suggesting that additional factors, such as lifestyle habits, may be contributory.

Methods

We examined the relation between SCD, amyloid status, lifestyle habits (exercise, sleep), mood/anxiety, and demographic variables among 4481 cognitively unimpaired older adults who are being screened for a multi-site secondary prevention trial (A4 screen data; mean ±SD: age = 71.3 ±4.7, education = 16.6 ±2.8, 59% women, 96% non-Hispanic or Latino, 92% White].

Results

On the Cognitive Function Index (CFI) participants endorsed higher concerns compared to SPs. Participant concerns were associated with older age, positive amyloid status, worse mood/anxiety, lower education, and lower exercise, whereas SP concerns were associated with older participant age, male gender of participant, positive amyloid status of participant, and worse participant-reported mood/anxiety.

Discussion

Findings suggest that modifiable/lifestyle factors (e.g., exercise, education) may be associated with participant concerns among cognitively unimpaired individuals and highlight the importance of further examining how modifiable factors impact participant- and SP-reported concerns, which may inform trial recruitment and clinical interventions.

Neuroanatomical and neurocognitive changes associated with subjective cognitive decline

Introduction

Subjective Cognitive Decline (SCD) can progress to mild cognitive impairment (MCI) and Alzheimer's disease (AD) dementia and thus may represent a preclinical stage of the AD continuum. However, evidence about structural changes observed in the brain during SCD remains inconsistent.

Materials and methods

This cross-sectional study aimed to evaluate, in subjects recruited from the CompAS project, neurocognitive and neurostructural differences between a group of forty-nine control subjects and forty-nine individuals who met the diagnostic criteria for SCD and exhibited high levels of subjective cognitive complaints (SCCs). Structural magnetic resonance imaging was used to compare neuroanatomical differences in brain volume and cortical thickness between both groups.

Results

Relative to the control group, the SCD group displayed structural changes involving frontal, parietal, and medial temporal lobe regions of critical importance in AD etiology and functionally related to several cognitive domains, including executive control, attention, memory, and language.

Conclusion

Despite the absence of clinical deficits, SCD may constitute a preclinical entity with a similar (although subtle) pattern of neuroanatomical changes to that observed in individuals with amnestic MCI or AD dementia.

Neural correlates of subjective cognitive decline in adults at high risk for Alzheimer's disease

Introduction

Recently, interest has emerged in subjective cognitive decline (SCD) as a potential precursor to Alzheimer's disease (AD) dementia. Whether individuals with SCD harbor brain alterations in midlife, when AD-related pathology begins, is yet to be elucidated. Furthermore, the role of apolipoprotein ε4 (APOE ε4) allele, a robust AD risk factor, in the relationship between SCD and brain alterations is unknown. We examined whether APOE genotype modulates the association of SCD with brain measures in individuals at high AD risk.

Methods

Middle-aged adults with parental history of AD dementia underwent magnetic resonance imaging (MRI) and the Memory Functioning Questionnaire. Regression analysis tested the extent to which SCD was associated with activation during an functional MRI (fMRI) working-memory task, and white-matter microstructure. APOE ε4 genotype was tested as a moderator.

Results

Among APOE ε4 carriers, but not among non-carriers, SCD was associated with higher activation in the anterior cingulate (p = 0.003), inferior, middle, and superior frontal cortices (p = 0.041, p = 0.048, p = 0.037, respectively); and with lower fractional anisotropy in the uncinate fasciculus (p = 0.002), adjusting for age, sex, and education.

Conclusion

In middle aged, cognitively normal individuals at high AD risk, higher SCD was associated with greater brain alterations possibly reflecting incipient AD pathology. When accompanied by a family history of AD and an APOE ε4 allele, SCD may have important clinical value, allowing a window for early intervention and for participants' stratification in AD prevention clinical trials.

CAG Repeats Within the Non-pathological Range in the HTT Gene Influence Personality Traits in Patients With Subjective Cognitive Decline: A 13-Year Follow-Up Study

OBJECTIVE

HTT is a gene containing a key region of CAG repeats. When expanded beyond 39 repeats, Huntington disease (HD) develops. HTT genes with <35 repeats are not associated with HD. The biological function of CAG repeat expansion below the non-pathological threshold is not well understood. In fact higher number of repeats in HTT confer advantageous changes in brain structure and general intelligence, but several studies focused on establishing the association between CAG expansions and susceptibility to psychiatric disturbances and to other neurodegenerative disease than HD. We hypothesized that HTT CAG repeat length below the pathological threshold might influence mood and personality traits in a longitudinal sample of individuals with Subjective Cognitive Decline.

METHODS

We included 54 patients with SCD. All patients underwent an extensive neuropsychological battery at baseline, APOE genotyping and analysis of HTT alleles. We used the Big Five Factors Questionnaire (BFFQ) and Hamilton Depression Rating Scale (HDRS), respectively, to assess personality traits of patients and depression at baseline. Patients who did not progress to Mild Cognitive Impairment (MCI) had at least 5-year follow-up time.

RESULTS

In the whole sample, CAG repeat number in the shorter HTT allele was inversely correlated with conscientiousness (Pearson = -0.364, p = 0.007). There was no correlation between HDRS and CAG repeats. During the follow-up, 14 patients [25.93% (95% C.I. = 14.24-37.61)] progressed to MCI (MCI⁺) and 40 [74.07% (95% C.I. = 62.39-85.76)] did not (MCI^-). When we performed the same analysis in the MCI⁺ group we found that: CAG repeat length on the shorter allele was inversely correlated with energy (Pearson = 0.639, p = 0.014) and conscientiousness (Pearson = -0.695, p = 0.006). CAG repeat length on the longer allele was inversely correlated with conscientiousness (Pearson = -0.901, p < 0.001) and directly correlated with emotional stability (Pearson = 0.639, p = 0.014). These associations were confirmed also by multivariate analysis. We found no correlations between BFFQ parameters and CAG repeats in the MCI^- group.

DISCUSSION

Personality traits and CAG repeat length in the intermediate range have been associated with progression of cognitive decline and neuropathological findings consistent with AD. We showed that CAG repeat lengths in the HTT gene within the non-pathological range influence personality traits.

Subjective Cognitive Decline in a Registry Sample: Relation to Psychiatric History, Loneliness, and Personality

BACKGROUND

With the increasing focus on prevention of Alzheimer's disease, there is need for characterization of preclinical populations. Local participant registries offer an opportunity to facilitate research engagement via remote data collection, inform recruitment, and characterize preclinical samples, including individuals with subjective cognitive decline.

OBJECTIVES

We sought to characterize subjective cognitive decline in a registry sample, as related to psychiatric history and related variables, including personality and loneliness, quality of life, and factors related to dementia risk (e.g., family history of dementia).

DESIGN, SETTING, PARTICIPANTS

Participants were 366 individuals (mean age=67.2 (range 50-88), 65% female, 94% white, 97% non-Hispanic or Latino, 82% with at least a bachelor's degree) with no reported history of mild cognitive impairment or dementia. All participants had expressed interest in research, primarily via community outreach events and prior research involvement. Data was collected via electronic surveys, distributed using REDCap. Electronic questionnaires included questions on demographic variables, subjective cognitive decline, quality of life, loneliness, and personality.

RESULTS

There was a high prevalence of risk factors for dementia in the registry sample (68% with family history of dementia, 31% with subjective cognitive decline). Subjective cognitive decline was more common in women and associated with history of depression, but not with family history of dementia. Subjective cognitive decline was also associated with lower conscientiousness and lower emotional stability, as well as higher loneliness and lower quality of life. Among participants who endorsed a psychiatric history, most reported onset more than 10 years prior, rather than within the last 10 years.

CONCLUSIONS

Subjective cognitive decline in a registry sample may be more strongly associated with longstanding psychiatric and personality variables, rather than family history of dementia, adding to the literature on characterization of subjective cognitive decline across different settings. These findings highlight the acceptability of remote data collection and the potential of registries to inform recruitment by characterizing registrants, which may help to stratify dementia risk and match participants to eligible trials.

Enhancing 'meaningfulness' of functional assessments: UK adaptation of the Amsterdam IADL questionnaire

OBJECTIVE

Commonly used measures of instrumental activities of daily living (IADL) do not capture activities for a technologically advancing society. This study aimed to adapt the proxy/informant-based Amsterdam IADL Questionnaire (A-IADL-Q) for use in the UK and develop a self-report version.

DESIGN

An iterative mixed method cross-cultural adaptation of the A-IADL-Q and the development of a self-report version involving a three-step design: (1) interviews and focus groups with lay and professional stakeholders to assess face and content validity; (2) a questionnaire to measure item relevance to older adults in the U.K.; (3) a pilot of the adapted questionnaire in people with cognitive impairment.

SETTING

Community settings in the UK.

PARTICIPANTS

One hundred and forty-eight participants took part across the three steps: (1) 14 dementia professionals; 8 people with subjective cognitive decline (SCD), mild cognitive impairment (MCI), or dementia due to Alzheimer's disease; and 6 relatives of people with MCI or dementia; (2) 92 older adults without cognitive impairment; and (3) 28 people with SCD or MCI.

MEASUREMENTS

The cultural relevance and applicability of the A-IADL-Q scale items were assessed using a 6-point Likert scale. Cognitive and functional performance was measured using a battery of cognitive and functional measures.

RESULTS

Iterative modifications to the scale resulted in a 55-item adapted version appropriate for UK use (A-IADL-Q-UK). Pilot data revealed that the new and revised items performed well. Four new items correlated with the weighted average score (Kendall's Tau -.388, -.445, -.497, -.569). An exploratory analysis of convergent validity found correlations in the expected direction with cognitive and functional measures.

CONCLUSION

The A-IADL-Q-UK provides a measurement of functional decline for use in the UK that captures culturally relevant activities. A new self-report version has been developed and is ready for testing. Further evaluation of the A-IADL-Q-UK for construct validity is now needed.

Mild Behavioral Impairment as a Marker of Cognitive Decline in Cognitively Normal Older Adults

OBJECTIVE

Mild behavioral impairment (MBI) is a neurobehavioral syndrome characterized by later life emergent neuropsychiatric symptoms (NPS) that represent an at-risk state for incident cognitive decline and dementia in people with mild cognitive impairment (MCI). We undertook a study to determine whether MBI was associated with progressive changes in neuropsychological performance in people without significant cognitive impairment.

METHODS

A total of 9,931 older adults enrolled in the PROTECT study who did not have MCI or dementia undertook a comprehensive neuropsychological battery measuring attention, reasoning, executive function, and working memory at baseline and 1 year. MBI was ascertained using self-administration of the Mild Behavioral Impairment Checklist at 1 year, and participants were grouped according to MBI status: No Symptoms, Intermediate NPS and MBI. All assessments were completed online, and data analyzed using mixed-effects model repeated measures analysis of covariance.

RESULTS

A total of 949 (10%) people had MBI. These individuals had significantly worse cognitive performance at baseline and significantly greater decline over 1 year in the four composite cognitive scores measuring attentional intensity (F [2,8578] = 3.97; p = 0.019), sustained attention (F [2,8578] = 18.63; p <0.0001), attentional fluctuation (F [2,8578] = 10.13; p <0.0001) and working memory (F [2,9895] = 13.1; p <0.0001).

CONCLUSION

Our novel findings show that MBI is associated with faster decline in attention and working memory in this cognitively normal sample. MBI may be an earlier marker of neurodegenerative disease than MCI, captured at the stage of subjective cognitive decline or before, raising the possibility that MBI represents a novel target for dementia clinical trials or prevention strategies.

Amyloid-β Load Is Related to Worries, but Not to Severity of Cognitive Complaints in Individuals With Subjective Cognitive Decline: The SCIENCe Project

Objective: Subjective cognitive decline (SCD) is associated with an increased risk of Alzheimer's Disease (AD). Early disease processes, such as amyloid-β aggregation measured with quantitative PET, may help to explain the phenotype of SCD. The aim of this study was to investigate whether quantitative amyloid-β load is associated with both self- and informant-reported cognitive complaints and memory deficit awareness in individuals with SCD. Methods: We included 106 SCD patients (mean ± SD age: 64 ± 8, 45%F) with 90 min dynamic [¹⁸F]florbetapir PET scans. We used the following questionnaires to assess SCD severity: cognitive change index (CCI, self and informant reports; 2 × 20 items), subjective cognitive functioning (SCF, four items), and five questions "Do you have complaints?" (yes/no) for memory, attention, organization and language), and "Does this worry you? (yes/no)." The Rivermead Behavioral Memory Test (RBMT)-Stories (immediate and delayed recall) was used to assess objective episodic memory. To investigate the level of self-awareness, we calculated a memory deficit awareness index (Z-transformed (inverted self-reported CCI minus episodic memory); higher index, heightened self-awareness) and a self-proxy index (Z-transformed self- minus informant-reported CCI). Mean cortical [¹⁸F]florbetapir binding potential (BP_ND) was derived from the PET data. Logistic and linear regression analyses, adjusted for age, sex, education, and depressive symptoms, were used to investigate associations between BP_ND and measures of SCD. Results: Higher mean cortical [¹⁸F]florbetapir BP_ND was associated with SCD-related worries (odds ratio = 1.76 [95%CI = 1.07 ± 2.90]), but not with other SCD questionnaires (informant and self-report CCI or SCF, total scores or individual items, all p > 0.05). In addition, higher mean cortical [¹⁸F]florbetapir BP_ND was associated with a higher memory deficit awareness index (Beta = 0.55), with an interaction between BP_ND and education (p = 0.002). There were no associations between [¹⁸F]florbetapir BP_ND and self-proxy index (Beta = 0.11). Conclusion: Amyloid-β deposition was associated with SCD-related worries and heightened memory deficit awareness (i.e., hypernosognosia), but not with severity of cognitive complaints. Our findings indicate that worries about self-perceived decline may reflect an early symptom of amyloid-β related pathology rather than subjective cognitive functioning.

Awareness of memory deficits in subjective cognitive decline, mild cognitive impairment, Alzheimer's disease and Parkinson's disease

BACKGROUND

Impaired awareness of memory deficits has been recognized as a common phenomenon in Alzheimer's disease (AD) and research is now increasingly focusing on awareness in groups at risk for future dementia. This study aimed to determine whether levels of awareness differ among healthy elderly people and patients with subjective cognitive decline (SCD), amnestic and non-amnestic subtypes of mild cognitive impairment (aMCI, naMCI), Alzheimer's disease (AD) and Parkinson's disease (PD), to explore correlates of awareness and to establish frequencies of memory over- and underestimation within each diagnostic group.

METHODS

756 consecutive outpatients of a memory clinic and 211 healthy controls underwent thorough neuropsychological testing. Impairment of awareness was measured as the difference between subjective memory appraisals (16-item questionnaire on current memory-related problems in everyday life) and objective memory performance (15-item delayed recall task). Subgroups of over- and underestimators were classified using percentile ranks of controls.

RESULTS

At group level, awareness significantly decreased along the naMCI→aMCI→AD continuum, with naMCI patients showing a tendency towards overestimation of memory dysfunction. PD patients showed accurate self-appraisals as long as memory function was largely unaffected. However, there was a considerable between-group overlap in awareness scores. Furthermore, different correlates of awareness were observed depending on the diagnostic group. In general, unawareness seems to be associated with decreased cognitive performance in various domains (especially memory), higher age and lower levels of depression and self-reported functional impairment.

CONCLUSION

Impaired awareness is an important symptom in aMCI. Yet, given the considerable variability in awareness scores, longitudinal studies are required to evaluate their predictive power.