Current directions in tau research: Highlights from Tau 2020

Studies supporting a strong association between tau deposition and neuronal loss, neurodegeneration, and cognitive decline have heightened the allure of tau and tau-related mechanisms as therapeutic targets. In February 2020, leading tau experts from around the world convened for the first-ever Tau2020 Global Conference in Washington, DC, co-organized and cosponsored by the Rainwater Charitable Foundation, the Alzheimer's Association, and CurePSP. Representing academia, industry, government, and the philanthropic sector, presenters and attendees discussed recent advances and current directions in tau research. The meeting provided a unique opportunity to move tau research forward by fostering global partnerships among academia, industry, and other stakeholders and by providing support for new drug discovery programs, groundbreaking research, and emerging tau researchers. The meeting also provided an opportunity for experts to present critical research-advancing tools and insights that are now rapidly accelerating the pace of tau research.

Two Year Outcomes, Cognitive and Behavioral Markers of Decline in Healthy, Cognitively Normal Older Persons with Global Deterioration Scale Stage 2 (Subjective Cognitive Decline with Impairment)

BACKGROUND

Little is known with respect to behavioral markers of subjective cognitive decline (SCD), a condition initially described in association with Global Deterioration Scale (GDS) stage 2.

OBJECTIVE

Two-year interval behavioral markers were investigated herein.

METHODS

Subjects from a published 7-year outcome study of GDS stage 2 subjects were selected. This study had demonstrated a hazard ratio of 4.5 for progression of GDS stage 2, in comparison with GDS stage 1 (no subjective or objective cognitive decline) subjects, after controlling for demographic and temporal variables. Because GDS 2 subjects have previously demonstrated impairment in comparison with healthy persons free of complaints, we herein suggest the terminology "SCD(I)" for these persons. 98 SCD(I) persons, 63 women and 35 men, mean baseline age, 67.12±8.75 years, with a mean educational background of 15.55±2.60 years, and mean baseline MMSE scores of 28.9±1.24 were followed for 2.13±0.30 years.

RESULTS

Observed annual decline on the GDS was 6.701% per annum, very close to a 1986 published estimate. At follow up, the MMSE, and 7 of 8 psychometric tests did not decline significantly. Of 21 Hamilton Depression Scale items, 2 improved and the remainder were unchanged. Anxieties declined from multiple perspectives. The Brief Cognitive Rating Scale (BCRS) declined significantly (p < 0.001), with component declines in Remote memory (p < 0.01), and Functioning/self-care (p = 0.01).

CONCLUSION

SCD(I) persons decline at an annual rate of approximately 6.7% /year from several recent studies. The BCRS assessments and the Digit Symbol Substitution Test can be sensitive measures for future studies of progression mitigation.

Subjective cognitive decline and rates of incident Alzheimer's disease and non-Alzheimer's disease dementia

Introduction:

In this multicenter study on subjective cognitive decline (SCD) in community-based and memory clinic settings, we assessed the (1) incidence of Alzheimer’s disease (AD) and non-AD dementia and (2) determinants of progression to dementia.

Methods:

Eleven cohorts provided 2978 participants with SCD and 1391 controls. We estimated dementia incidence and identified risk factors using Cox proportional hazards models.

Results:

In SCD, incidence of dementia was 17.7 (95% Poisson confidence interval 15.2–20.3)/1000 person-years (AD: 11.5 [9.6–13.7], non-AD: 6.1 [4.7–7.7]), compared with 14.2 (11.3–17.6) in controls (AD: 10.1 [7.7–13.0], non-AD: 4.1 [2.6–6.0]). The risk of dementia was strongly increased in SCD in a memory clinic setting but less so in a community-based setting. In addition, higher age (hazard ratio 1.1 [95% confidence interval 1.1–1.1]), lower Mini-Mental State Examination (0.7 [0.66–0.8]), and apolipoprotein E ε4 (1.8 [1.3–2.5]) increased the risk of dementia.

Discussion:

SCD can precede both AD and non-AD dementia. Despite their younger age, individuals with SCD in a memory clinic setting have a higher risk of dementia than those in community-based cohorts.

A conceptual framework for research on subjective cognitive decline in preclinical Alzheimer's disease

There is increasing evidence that subjective cognitive decline (SCD) in individuals with unimpaired performance on cognitive tests may represent the first symptomatic manifestation of Alzheimer's disease (AD). The research on SCD in early AD, however, is limited by the absence of common standards. The working group of the Subjective Cognitive Decline Initiative (SCD-I) addressed this deficiency by reaching consensus on terminology and on a conceptual framework for research on SCD in AD. In this publication, research criteria for SCD in pre-mild cognitive impairment (MCI) are presented. In addition, a list of core features proposed for reporting in SCD studies is provided, which will enable comparability of research across different settings. Finally, a set of features is presented, which in accordance with current knowledge, increases the likelihood of the presence of preclinical AD in individuals with SCD. This list is referred to as SCD plus.

The BEHAVE-AD assessment system: a perspective, a commentary on new findings, and a historical review

BACKGROUND

Behavioral and psychological symptoms of dementia (BPSD) and associated disturbances in Alzheimer's disease (AD) are a source of distress and burden for spouses, professional caregivers, and others with responsibilities for the care of individuals with AD. BPSD with behavioral disturbances are also associated with more rapid institutionalization and increased morbidity and mortality for persons with AD.

OBJECTIVES

In this review and commentary, we discuss the history of the development of BPSD and behavioral disturbance assessments, which are distinct from those evaluating cognitive and functional symptoms of AD. In particular, we review the informant-based Behavioral Pathology in Alzheimer's Disease Rating Scale (BEHAVE-AD), the related, potentially more sensitive, BEHAVE-AD Frequency-Weighted Severity Scale (BEHAVE-AD-FW), and the direct subject evaluation-based Empirical BEHAVE-AD Rating Scale (E-BEHAVE-AD). The kinds of medications that alleviate behavioral symptoms on these measures as well as the problems and possibilities for further advances with these medications are discussed. Finally, the importance of distinguishing BPSD and behavioral disturbance remediation in AD from the treatment of cognitive decline and other aspects of AD is emphasized in the context of appropriate assessment methodology. The objective of this paper is to provide a framework for further advances in the treatment of BPSD and associated behavioral disturbances in AD and, consequently, a framework for continuing improvements in the lives of individuals with AD and those who share the burden of the disease with the AD person.

Using AD biomarker research results for clinical care: a survey of ADNI investigators

OBJECTIVE

To inform whether the Alzheimer's Disease Neuroimaging Initiative (ADNI) should change its policy of not returning research results to ADNI participants, we surveyed investigators and research staff about disclosing ADNI biomarker information to research participants, with particular emphasis on amyloid imaging results.

METHODS

In April 2012, just before Food and Drug Administration approval of the amyloid-binding radiotracer, florbetapir, all ADNI investigators and personnel were recruited to complete an anonymous online survey that contained fixed choice and free-text questions.

RESULTS

Although ADNI participants often requested amyloid imaging results (the proportions of investigators who reported requests from more than half of their participants with normal cognition or mild cognitive impairment were 20% and 22%, respectively), across all diagnostic groups, the majority of ADNI investigators (approximately 90%) did not return amyloid imaging results to ADNI participants. However, the majority of investigators reported that, if the Food and Drug Administration approved florbetapir, they would support the return of amyloid imaging results to participants with mild cognitive impairment and normal cognition, but they emphasized the need for guidance on how to provide these results to participants and for research to assess the value of returning results as well as how returning results will affect study validity and participant well-being.

CONCLUSIONS

A majority of ADNI investigators support returning amyloid imaging results to ADNI participants. The findings that they want guidance on how to do this and research on the impact of disclosure suggest how to develop and monitor a disclosure process.

Outcome over seven years of healthy adults with and without subjective cognitive impairment

BACKGROUND

Subjective cognitive impairment (SCI) in older persons without manifest symptomatology is a common condition with a largely unclear prognosis. We hypothesized that (1) examining outcome for a sufficient period by using conversion to mild cognitive impairment (MCI) or dementia would clarify SCI prognosis, and (2) with the aforementioned procedures, the prognosis of SCI subjects would differ significantly from that of demographically matched healthy subjects, free of SCI, termed no cognitive impairment (NCI) subjects.

METHODS

A consecutive series of healthy subjects, aged > or =40 years, presenting with NCI or SCI to a brain aging and dementia research center during a 14-year interval, were studied and followed up during an 18-year observation window. The study population (60 NCI, 200 SCI, 60% female) had a mean age of 67.2 +/- 9.1 years, was well-educated (mean, 15.5 +/- 2.7 years), and cognitively normal (Mini-Mental State Examination, 29.1 +/- 1.2).

RESULTS

A total of 213 subjects (81.9% of the study population) were followed up. Follow-up occurred during a mean period of 6.8 +/- 3.4 years, and subjects had a mean of 2.9 +/- 1.6 follow-up visits. Seven NCI (14.9%) and 90 SCI (54.2%) subjects declined (P < .0001). Of NCI decliners, five declined to MCI and two to probable Alzheimer's disease. Of SCI decliners, 71 declined to MCI and 19 to dementia diagnoses. Controlling for baseline demographic variables and follow-up time, Weibull proportional hazards model revealed increased decline in SCI subjects (hazard ratio, 4.5; 95% confidence interval, 1.9-10.3), whereas the accelerated failure time model analysis with an underlying Weibull survival function showed that SCI subjects declined more rapidly, at 60% of the rate of NCI subjects (95% confidence interval, 0.45-0.80). Furthermore, mean time to decline was 3.5 years longer for NCI than for SCI subjects (P = .0003).

CONCLUSIONS

These results indicate that SCI in subjects with normal cognition is a harbinger of further decline in most subjects during a 7-year mean follow-up interval. Relevance for community populations should be investigated, and prevention studies in this at-risk population should be explored.

Treatment of memory disorders in epilepsy

Impaired memory is a common and often debilitating complaint in patients with epilepsy. Overlapping variables such as seizure control, attentional dysfunction, and mood disorders further complicate diagnosis and management. Direct therapy for memory deficits associated with epilepsy is rarely attempted. The varied pharmacological (AED selection, cholinesterase inhibitors, stimulants, antidepressants, and herbal supplements) and nonpharmacological approaches to cognitive remediation in epilepsy patients are reviewed.

Triangular backgrounds shift the bias of line bisection performance in hemispatial neglect

OBJECTIVE

Patients with left neglect on line bisection show normal implicit sensitivity to manipulations of both the stimulus and the visual background. Three experiments were designed to define this sensitivity more exactly.

METHODS

Normal controls and patients with left neglect performed a series of horizontal line bisection tasks. Independent variables were the configurations of the backgrounds for the line-rectangle, square, circle, left and right pointing isosceles triangles-and whether the background was the shape of the piece of paper or an outline drawn on a standard piece of paper. In a separate experiment different components of the triangle were outlined on a piece of paper. Deviation from true midpoint was calculated.

RESULTS

Simply placing the target lines in a symmetric background such as a square or circle did not reliably reduce neglect. A triangle asymmetric in the horizontal plane caused a shift in bisection away from the triangle's vertex. With right pointing triangles the perceived midpoint shifted to the left of true centre (crossed over). The effects of the triangles were comparable in the patients and the controls when controlled for baseline bisection bias. The critical components of the triangles were the angular legs. This effect of background was not influenced by lesion site or by hemianopia.

CONCLUSIONS

Patients with left visual neglect remain sensitive to covert manipulations of the visual background that implicitly shift the perceived midpoint of a horizontal line. This effect is strong enough to eliminate neglect on a bisection task. The mechanism of this effect is expressed through preattentive visual capacities.

The Frontal Lobes, Epilepsy, and Behavior

The frontal lobes have been overshadowed by the temporal lobes in the vast literature addressing the neurobehavioral and psychological perspectives of epilepsy. The purpose of this review is to summarize contemporary anatomicobehavioral correlations and to highlight the frontal lobe contributions to the neurology, neuropsychology, and neuropsychiatry of epilepsy, in general, and to temporal lobe epilepsy (TLE) and frontal lobe epilepsy (FLE), in particular. Much evidence has accumulated suggesting that focal epileptogenic tissue may have effects on distant neural systems. Data supporting the case that the frontal regions are preferentially affected in TLE are presented. Emphasis is placed on the results of numerous functional imaging studies demonstrating correlations between frontal hypoperfusion and cognitive or mood impairments in patients with TLE.