Do people with Alzheimer's disease improve with repeated testing? Unpacking the role of content and context in retest effects

Pick a PACC: Comparing domain-specific and general cognitive composites in Alzheimer disease research

OBJECTIVE

We aimed to illustrate how complex cognitive data can be used to create domain-specific and general cognitive composites relevant to Alzheimer disease research.

METHOD

Using equipercentile equating, we combined data from the Charles F. and Joanne Knight Alzheimer Disease Research Center that spanned multiple iterations of the Uniform Data Set. Exploratory factor analyses revealed four domain-specific composites representing episodic memory, semantic memory, working memory, and attention/processing speed. The previously defined preclinical Alzheimer disease cognitive composite (PACC) and a novel alternative, the Knight-PACC, were also computed alongside a global composite comprising all available tests. These three composites allowed us to compare the usefulness of domain and general composites in the context of predicting common Alzheimer disease biomarkers.

RESULTS

General composites slightly outperformed domain-specific metrics in predicting imaging-derived amyloid, tau, and neurodegeneration burden. Power analyses revealed that the global, Knight-PACC, and attention and processing speed composites would require the smallest sample sizes to detect cognitive change in a clinical trial, while the Alzheimer Disease Cooperative Study-PACC required two to three times as many participants.

CONCLUSIONS

Analyses of cognition with the Knight-PACC and our domain-specific composites offer researchers flexibility by providing validated outcome assessments that can equate across test versions to answer a wide range of questions regarding cognitive decline in normal aging and neurodegenerative disease. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Retrieval Practice Improves Exam Performance as a Function of Review Question Number and Format

INTRODUCTION

Although retrieval practice is a well-established method of improving learning, it is unclear whether review question format matters or how many review questions are needed to maximize the effects of retrieval practice.

REVIEW OF LITERATURE

Inconsistent findings are reported regarding review question format, and no studies were conducted in physical therapy education programs. A positive relationship is reported between review question number and exam performance, but no studies estimate the number of review questions needed to maximize retention of specific learning objectives.

SUBJECTS

Eighty-eight second-year Doctor of Physical Therapy students (baseline cohort = 42 students, intervention cohort = 46 students).

METHODS

Exam questions were randomly assigned into different review categories. Some exam questions received no review, whereas other exam questions were reviewed with open-ended review questions or varying numbers of multiple-choice review questions. Performance on 160 multiple-choice exam questions was compared between review question categories using mixed-effects logistic regression models.

RESULTS

Both open-ended and multiple-choice review questions significantly improved exam question performance. Performance on exam questions improved most when more than one multiple-choice review question was provided. After controlling for exam question difficulty, multiple-choice review questions were superior to open-ended review questions.

DISCUSSION AND CONCLUSION

On multiple-choice exams, multiple-choice review questions are at least as effective as open-ended review questions. Given their ease of implementation, multiple-choice review questions are an efficient means to improve multiple-choice exam question performance.

Impact of Age on Cognitive Testing Practice Effects and Cardiorespiratory Responses

Objective: This study tested the hypothesis that healthy aging attenuates cognitive practice effects and, consequently, limits the familiarity-associated reductions in heart rate (HR) and breathing frequency (BF) responses during retesting. Methods: Twenty-one cognitively normal older and younger adults (65 ± 2 vs. 26 ± 1 years old) participated in the study. Mini-Mental State Examination (MMSE), Digit-Span-Test (DST), Trail Making Test (TMT-B), and California Verbal Learning Test (CVLT-II) were administered twice at 3-week intervals, while HR and BF were monitored by electrocardiography and plethysmography, respectively. Results: Cognitive performances were not affected by the age factor, and the retest factor only affected CVLT-II. HR and BF increased only in the younger adults (p < .01) during cognitive tests; retesting attenuated these responses (retest factor p < .01). Long-delay free-recall in CVLT-II was unchanged in cognitively normal older versus younger adults. Healthy aging did not diminish short-term memory assessed by DST and CVLT-II short-delay or long-delay free-recalls. Conclusions: Only CVLT-II, but not MMSE, DST or TMT-B, demonstrated cognitive retesting practice effects in the younger and older adults. Cognitive testing at 3-week intervals in cognitively normal older and younger subjects revealed divergent cardiorespiratory responses to MMSE, DST, and TMT-B cognitive testing, particularly HR, which increased only in younger adults and to a lesser extent during retesting despite the absence of practice effects.

Impact of cataract surgery on cognitive impairment in older people

OBJECTIVES

To examine the impact of cataract surgery on mild cognitive impairment (MCI) and dementia in older people.

METHODS

This prospective observational study included patients aged 75 years and older who underwent cataract surgery between 2019 and 2021. Mini-mental state examination (MMSE) and MMSE for the visually impaired (MMSE-blind) were measured to evaluate cognitive function before and 3 months after cataract surgery. MMSE score at baseline was used to categorize patients into dementia (MMSE ≤ 23) and MCI groups (23 < MMSE ≤ 27). Logistic regression models were used to estimate associations between improvement in cognitive function and other factors.

RESULTS

Of 132 patients screened for inclusion in the study, 88 met the inclusion criteria; 39 patients were assigned to the dementia group (mean age, 85.7 ± 4.2 years) and 49 to the MCI group (mean age, 84.2 ± 3.4 years). The MCI group showed significant improvement from before to after surgery in the MMSE score (25.65 ± 1.03 vs. 27.08 ± 1.99, respectively, p < 0.001) and MMSE-blind score (18.04 ± 1.14 vs. 19.41 ± 2.01, respectively, p < 0.001). Cognitive function improved significantly in the MCI group compared with the dementia group (odds ratio, 2.85; 95% confidence interval, 1.02-7.97; and p = 0.046).

CONCLUSIONS

Cataract surgery significantly increases cognitive test scores in older patients with MCI. After cataract surgery, the likelihood of improvement in cognitive function may be highly dependent on a patient's preoperative cognitive state.

Pragmatic approaches to handling practice effects in longitudinal cognitive aging research

INTRODUCTION

The challenge of accounting for practice effects (PEs) when modeling cognitive change was amplified by the COVID-19 pandemic, which introduced period and mode effects that may bias the estimation of cognitive trajectory.

METHODS

In three Kaiser Permanente Northern California prospective cohorts, we compared predicted cognitive trajectories and the association of grip strength with cognitive decline using three approaches: (1) no acknowledgment of PE, (2) inclusion of a wave indicator, and (3) constraining PE based on a preliminary model (APM) fit using a subset of the data.

RESULTS

APM-based correction for PEs based on balanced, pre-pandemic data, and with current age as the timescale produced the smallest discrepancy between within-person and between-person estimated age effects. Estimated associations between grip strength and cognitive decline were not sensitive to the approach used.

DISCUSSION

Constraining PEs based on a preliminary model is a flexible, pragmatic approach allowing for meaningful interpretation of cognitive change.

HIGHLIGHTS

The magnitude of practice effects (PEs) varied widely by study. When PEs were present, the three PE approaches resulted in divergent estimated age-related cognitive trajectories. Estimated age-related cognitive trajectories were sometimes implausible in models that did not account for PEs. The associations between grip strength and cognitive decline did not differ by the PE approach used. Constraining PEs based on estimates from a preliminary model allows for a meaningful interpretation of cognitive change.

Misinterpreting cognitive change over multiple timepoints: When practice effects meet age-related decline

OBJECTIVE

Practice effects (PE) on cognitive testing have been shown to delay detection of impairment and impede our ability to assess change. When decline over time is expected, as with older adults or progressive diseases, failure to adequately address PEs may lead to inaccurate conclusions because PEs artificially boost scores while pathology- or age-related decline reduces scores. Unlike most methods, a participant-replacement approach can separate pathology- or age-related decline from PEs; however, this approach has only been used across two timepoints. More than two timepoints make it possible to determine if PEs level out after the first follow-up, but it is analytically challenging because individuals may not be assessed at every timepoint.

METHOD

We examined 1,190 older adults who were cognitively unimpaired (n = 809) or had mild cognitive impairment (MCI; n = 381). Participants completed six neuropsychological measures at three timepoints (baseline, 12-month, 24-month). We implemented a participant-replacement method using generalized estimating equations in comparisons of matched returnees and replacements to calculate PEs.

RESULTS

Without accounting for PEs, cognitive function appeared to improve or stay the same. However, with the participant-replacement method, we observed significant PEs within both groups at all timepoints. PEs did not uniformly decrease across time; some-specifically on episodic memory measures-continued to increase beyond the first follow-up.

CONCLUSION

A replacement method of PE adjustment revealed significant PEs across two follow-ups. As expected in these older adults, accounting for PEs revealed cognitive decline. This, in turn, means earlier detection of cognitive deficits, including progression to MCI, and more accurate characterization of longitudinal change. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Four year practice effects on the RBANS in a longitudinal study of older adults

OBJECTIVE

The Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) is a widely used measure in neuropsychological assessment. Studies of practice effects on the RBANS have typically been assessed over one or two repeated assessments. The aim of the current study is to examine practice effects across four-years after baseline in a longitudinal study of cognitively healthy older adults.

METHOD

453 Participants from the Louisiana Aging Brain Study (LABrainS) completed the RBANS Form A on up to four annual assessments after baseline. Practice effects were calculated using a modified participants-replacement method where scores of returnees are compared to the baseline scores of matched participants with additional adjustment for attrition effects.

RESULTS

Practice effects were observed primarily in the immediate memory, delayed memory, and total score indices. These index scores continued to increase with repeated assessments.

CONCLUSIONS

These findings extend past work on the RBANS showing the susceptibility of memory measures to practice effects. Given that memory and total score indices of the RBANS have the most robust relationships with pathological cognitive decline, these findings raise concerns about the ability to recruit those at risk for decline from longitudinal studies using the same form of the RBANS for multiple years.

Dependence of learning outcomes in flipped and lecture classrooms on review questions: A randomized controlled trial and observational study

PURPOSE

The effects of class structure (i.e., lecture vs. flipped) and repeated review on: 1) exam scores and 2) student perceptions of learning were compared in a prospective randomized controlled trial (Study 1) and a retrospective cohort study (Study 2).

METHODS

In Study 1, 42 second year students in a Doctor of Physical Therapy program were randomized to either a lecture or flipped section of a neurobiology class. Both sections incorporated repeated review. In Study 2, exam scores were retrospectively compared between two cohorts: a lecture cohort without repeated review (n = 42) and a flipped cohort with repeated review (n = 46). In both studies, outcomes of interest were exam scores and student surveys.

RESULTS

In Study 1, students in the lecture and flipped sections had similar exam averages (lecture = 76.7 ± 17%, flipped = 77.5 ± 17%, p = 0.73). Repeated review significantly improved exam scores by 12.0 percentage points (95% CI: 8.0 to 16.0 percentage points) in the lecture section and 10.8 percentage points (95% CI: 6.9 to 14.8 percentage points) in the flipped section. The flipped section reported higher levels of satisfaction and perceived learning. In Study 2, the flipped cohort had significantly higher exam scores than the lecture cohort (lecture = 70.2 ± 6.9%, flipped = 83.4 ± 7.7%, p < 0.0001). Student satisfaction and perceived learning were similar in both cohorts.

CONCLUSION

Exam scores improve with review questions and quizzes provided in a class, both in a lecture or flipped classroom.

The development of an automated machine learning pipeline for the detection of Alzheimer's Disease

Although Alzheimer's disease is the most prevalent form of dementia, there are no treatments capable of slowing disease progression. A lack of reliable disease endpoints and/or biomarkers contributes in part to the absence of effective therapies. Using machine learning to analyze EEG offers a possible solution to overcome many of the limitations of current diagnostic modalities. Here we develop a logistic regression model with an accuracy of 81% that addresses many of the shortcomings of previous works. To our knowledge, no other study has been able to solve the following problems simultaneously: (1) a lack of automation and unbiased removal of artifacts, (2) a dependence on a high level of expertise in data pre-processing and ML for non-automated processes, (3) the need for very large sample sizes and accurate EEG source localization using high density systems, (4) and a reliance on black box ML approaches such as deep neural nets with unexplainable feature selection. This study presents a proof-of-concept for an automated and scalable technology that could potentially be used to diagnose AD in clinical settings as an adjunct to conventional neuropsychological testing, thus enhancing efficiency, reproducibility, and practicality of AD diagnosis.

Practice effects in cognitive assessments three years later in non-carriers but not in symptom-free mutation carriers of autosomal-dominant Alzheimer's disease: Exemplifying procedural learning and memory?

Practice effects (PEs) defined as an improvement of performance in cognition due to repeated assessments between sessions are well known in unimpaired individuals, while less is known about impaired cognition and particularly in latent brain disease as autosomal-dominant Alzheimer's disease. The purpose was to evaluate the general (across tests/domains) and domain-specific PE calculated as the annual rate of change (ARC) in relation to years to the estimated disease onset (YECO) and in four groups of AD: asymptomatic mutation carriers (aAD, n = 19), prodromal, i.e., symptomatic mutation carriers, criteria for AD diagnosis not fulfilled (pAD, n = 4) and mutation carriers diagnosed with AD (dAD, n = 6) as well as mutation non-carriers from the AD families serving as a healthy comparison group (HC, n = 35). Cognition was assessed at baseline and follow-up about 3 years later by 12 tests covering six domains. The aAD and HC groups were comparable at baseline in demographic characteristics (age, gender, and education), when they were in their early forties, while the pAD and dAD groups were older and cognitively impaired. The results on mean ARC for the four groups were significantly different, small, positive, and age-insensitive in the HC group, while ARC was negative and declined with time/disease advancement in AD. The differences between HC and aAD groups in mean ARC and domain-specific ARC were not significant, indicating a subtle PE in aAD in the early preclinical stage of AD. In the symptomatic stages of AD, there was no PE probably due to cognitive disease-related progression. PEs were the largest in the verbal domain in both the HC and aAD groups, indicating a relationship with cognitive vulnerability. The group-related difference in mean ARC was predominant in timekeeping tests. To conclude, the practice effect in over 3 years was suggested to be linked to procedural learning and memory.

Practice Effects in Mild Cognitive Impairment Increase Reversion Rates and Delay Detection of New Impairments

Objective

Cognitive practice effects (PEs) can delay detection of progression from cognitively unimpaired to mild cognitive impairment (MCI). They also reduce diagnostic accuracy as suggested by biomarker positivity data. Even among those who decline, PEs can mask steeper declines by inflating cognitive scores. Within MCI samples, PEs may increase reversion rates and thus impede detection of further impairment. Within an MCI sample at baseline, we evaluated how PEs impact prevalence, reversion rates, and dementia progression after 1 year.

Methods

We examined 329 baseline Alzheimer's Disease Neuroimaging Initiative MCI participants (mean age = 73.1; SD = 7.4). We identified test-naïve participants who were demographically matched to returnees at their 1-year follow-up. Since the only major difference between groups was that one completed testing once and the other twice, comparison of scores in each group yielded PEs. PEs were subtracted from each test to yield PE-adjusted scores. Biomarkers included cerebrospinal fluid phosphorylated tau and amyloid beta. Cox proportional models predicted time until first dementia diagnosis using PE-unadjusted and PE-adjusted diagnoses.

Results

Accounting for PEs increased MCI prevalence at follow-up by 9.2% (272 vs. 249 MCI), and reduced reversion to normal by 28.8% (57 vs. 80 reverters). PEs also increased stability of single-domain MCI by 12.0% (164 vs. 147). Compared to PE-unadjusted diagnoses, use of PE-adjusted follow-up diagnoses led to a twofold increase in hazard ratios for incident dementia. We classified individuals as false reverters if they reverted to cognitively unimpaired status based on PE-unadjusted scores, but remained classified as MCI cases after accounting for PEs. When amyloid and tau positivity were examined together, 72.2% of these false reverters were positive for at least one biomarker.

Interpretation

Even when PEs are small, they can meaningfully change whether some individuals with MCI retain the diagnosis at a 1-year follow-up. Accounting for PEs resulted in increased MCI prevalence and altered stability/reversion rates. This improved diagnostic accuracy also increased the dementia-predicting ability of MCI diagnoses.

Cognitive practice effects delay diagnosis of MCI: Implications for clinical trials

INTRODUCTION

Practice effects (PEs) on cognitive tests obscure decline, thereby delaying detection of mild cognitive impairment (MCI). Importantly, PEs may be present even when there are performance declines, if scores would have been even lower without prior test exposure. We assessed how accounting for PEs using a replacement-participants method impacts incident MCI diagnosis.

METHODS

Of 889 baseline cognitively normal (CN) Alzheimer's Disease Neuroimaging Initiative (ADNI) participants, 722 returned 1 year later (mean age = 74.9 ± 6.8 at baseline). The scores of test-naïve demographically matched "replacement" participants who took tests for the first time were compared to returnee scores at follow-up. PEs-calculated as the difference between returnee follow-up scores and replacement participants scores-were subtracted from follow-up scores of returnees. PE-adjusted cognitive scores were then used to determine if individuals were below the impairment threshold for MCI. Cerebrospinal fluid amyloid beta, phosphorylated tau, and total tau were used for criterion validation. In addition, based on screening and recruitment numbers from a clinical trial of amyloid-positive individuals, we estimated the effect of earlier detection of MCI by accounting for cognitive PEs on a hypothetical clinical trial in which the key outcome was progression to MCI.

RESULTS

In the ADNI sample, PE-adjusted scores increased MCI incidence by 19% (P < .001), increased proportion of amyloid-positive MCI cases (+12%), and reduced proportion of amyloid-positive CNs (-5%; P's < .04). Additional calculations showed that the earlier detection and increased MCI incidence would also substantially reduce necessary sample size and study duration for a clinical trial of progression to MCI. Cost savings were estimated at ≈$5.41 million.

DISCUSSION

Detecting MCI as early as possible is of obvious importance. Accounting for cognitive PEs with the replacement-participants method leads to earlier detection of MCI, improved diagnostic accuracy, and can lead to multi-million-dollar cost reductions for clinical trials.

Longitudinal effects of physical exercise on health-related outcomes based on frailty status in community-dwelling older adults

AIM

To clarify the difference in the longitudinal effects of physical exercise on health-related outcomes according to the baseline frailty status (frail or non-frail) in community-dwelling older adults.

METHODS

Participants included 177 adults aged ≥65 years who carried out multicomponent physical exercises (strength, aerobic, gait and balance) for 40 min, one to three times per week, for 1 year at a day-care center. Bodyweight, comfortable walking speed, 6-min walking distance and Mini-Mental State Examination were measured at baseline and every 3 months. For longitudinal trend, we analyzed the change in scores from baseline for each outcome using the linear mixed effects model. Fixed effects included "group" (frail or non-frail), "time" (4 time points every 3 months, from 3 to 12 months) and "interaction between group and time."

RESULTS

The effect sizes from baseline showed almost all positive values for each outcome. The linear mixed effects model showed significant effects on "interaction between group and time" in changes in bodyweight (P = 0.033), "group" in changes in walking speed (P = 0.013) and "time" in changes in the Mini-Mental State Examination (P < 0.001). Bodyweight showed a decreasing trend in the non-frail group after 3 months, unlike in the frail group. For walking speed, moderate effect sizes (d = 0.67-0.74) were sustained over time in the frail group, as did lesser effect sizes (d = 0.26-0.40) in the non-frail group.

CONCLUSIONS

Exercise-based multicomponent interventions were effective for both groups. The longitudinal effects on walking speed and bodyweight were greater in the frail group. Geriatr Gerontol Int 2022; ••: ••-••.

Chewing function and related parameters as a function of the degree of dementia: Is there a link between the brain and the mouth?

Background

To date, no study has investigated the association between chewing function and related parameters as a function of the degree of dementia using a finer subdivision of the values of the Mini‐Mental State Examination (MMSE).

Objective

This study aimed to investigate the differences in chewing function and related parameters as a function of the degree of dementia.

Methods

An analysis of cross‐sectional data obtained from the OrBiD (Oral Health, Bite Force, and Dementia) pilot study was performed. The participants were stratified into five groups based on the outcomes of the MMSE (no dementia, MMSE 28–30; mild cognitive impairment, MMSE 25–27; mild dementia, MMSE 18–24; moderate dementia, MMSE 10–17; severe dementia, MMSE <10). The chewing efficiency, maximum occlusal force and related parameters (number of supporting zones, number of teeth, Eichner index, tooth/denture status, denture quality, and dental treatment needs) were recorded.

Results

The MMSE groups showed significantly different chewing efficiencies (p = .003, Jonckheere‐Terpstra test) and maximum occlusal forces (p = .003, Jonckheere‐Terpstra test), but the number of supporting zones (p = .055, chi‐square test) and the number of natural teeth (p = .126, chi‐square test) were not different. The Eichner index, tooth/denture status, denture quality and dental treatment need showed no significant associations with the degree of dementia.

Conclusion

An improvement in the usability of the measurement methods for assessing chewing function in people with dementia is needed. Research involving people with dementia is necessary because the nutritional situation often deteriorates rapidly within a multifactorial system, which includes chewing ability and oral health.

Predicting Dementia With Prefrontal Electroencephalography and Event-Related Potential

Objective: To examine whether prefrontal electroencephalography (EEG) can be used for screening dementia.

Methods: We estimated the global cognitive decline using the results of Mini-Mental Status Examination (MMSE), measurements of brain activity from resting-state EEG, responses elicited by auditory stimulation [sensory event-related potential (ERP)], and selective attention tasks (selective-attention ERP) from 122 elderly participants (dementia, 35; control, 87). We investigated that the association between MMSE and each EEG/ERP variable by using Pearson’s correlation coefficient and performing univariate linear regression analysis. Kernel density estimation was used to examine the distribution of each EEG/ERP variable in the dementia and non-dementia groups. Both Univariate and multiple logistic regression analyses with the estimated odds ratios were conducted to assess the associations between the EEG/ERP variables and dementia prevalence. To develop the predictive models, five-fold cross-validation was applied to multiple classification algorithms.

Results: Most prefrontal EEG/ERP variables, previously known to be associated with cognitive decline, show correlations with the MMSE score (strongest correlation has |r| = 0.68). Although variables such as the frontal asymmetry of the resting-state EEG are not well correlated with the MMSE score, they indicate risk factors for dementia. The selective-attention ERP and resting-state EEG variables outperform the MMSE scores in dementia prediction (areas under the receiver operating characteristic curve of 0.891, 0.824, and 0.803, respectively). In addition, combining EEG/ERP variables and MMSE scores improves the model predictive performance, whereas adding demographic risk factors do not improve the prediction accuracy.

Conclusion: Prefrontal EEG markers outperform MMSE scores in predicting dementia, and additional prediction accuracy is expected when combining them with MMSE scores.

Significance: Prefrontal EEG is effective for screening dementia when used independently or in combination with MMSE.

Cognitive Practice Effects Delay Diagnosis; Implications for Clinical Trials

OBJECTIVE

Practice effects on cognitive tests obscure decline, thereby delaying detection of mild cognitive impairment (MCI). This reduces opportunities for slowing Alzheimer's disease progression and can hinder clinical trials. Using a novel method, we assessed the ability of practice-effect-adjusted diagnoses to detect MCI earlier, and tested the validity of these diagnoses based on AD biomarkers.

METHODS

Of 889 Alzheimer's Disease Neuroimaging Initiative participants who were cognitively normal (CN) at baseline, 722 returned at 1-year-follow-up (mean age=74.9±6.8). Practice effects were calculated by comparing returnee scores at follow-up to demographically-matched individuals who had only taken the tests once, with an additional adjustment for attrition effects. Practice effects for each test were subtracted from follow-up scores. The lower scores put additional individuals below the impairment threshold for MCI. CSF amyloid-beta, phosphorylated tau, and total tau were measured at baseline and used for criterion validation.

RESULTS

Practice-effect-adjusted scores increased MCI incidence by 26% (p<.001). Adjustment increased proportions of amyloid-positive MCI cases (+20%) and reduced proportions of amyloid-positive CNs (-6%) (ps<.007). With the increased MCI base rate, adjustment for practice effects would reduce the sample size needed for detecting significant drug treatment effects by an average of 21%, which we demonstrate would result in multi-million-dollar savings in a clinical trial.

INTERPRETATION

Adjusting for practice effects on cognitive testing leads to earlier detection of MCI. When MCI is an outcome, this reduces recruitment needed for clinical trials, study duration, staff and participant burden, and can dramatically lower costs. Importantly, biomarker evidence also indicates improved diagnostic accuracy.

Lower practice effects as a marker of cognitive performance and dementia risk: A literature review

BACKGROUND

Practice effects (PEs) are improvements in performance after repeated exposure to test materials, and typically viewed as a source of bias in repeated cognitive assessments. We aimed to determine whether characterizing PEs could also provide a useful marker of early cognitive decline.

METHODS

We conducted a systematic review of the literature, searching PsycInfo (Ebsco) and PubMed databases for articles studying PEs in aging and dementia populations. Articles published between 1920 and 2019 were included.

RESULT

We identified 259 articles, of which 27 studied PEs as markers of cognitive performance. These studies consistently showed that smaller, less-robust PEs were associated with current diagnostic status and/or future cognitive decline. In addition, lower PEs were associated with Alzheimer's disease risk factors and neurodegeneration biomarkers.

CONCLUSION

PEs provide a potentially useful marker of cognitive decline, and could prove valuable as part of a cost-effective strategy to select individuals who are at-risk for dementia for future interventions.

One third of dementia cases can be prevented within the next 25 years by tackling risk factors. The case "for" and "against"

BACKGROUND

Recently, it has been suggested that up to a third of the dementia cases might be preventable. While prevention is always better than cure, this is particularly important in the field of dementia, as current interventions are not able to modify the disease. This article revises the evidence "for" and "against" dementia primary prevention.

DISCUSSION

Evidence "for" is sustained by the Lancet Commission on Dementia Prevention, Intervention and Care that noted a reduction of age-related incidence of dementia in high-income countries. Based on results from large cohort studies and using population attributable risk, the commission concluded that up to 35% of dementia cases could be prevented by modifying nine risk factors: low education, midlife hearing loss, obesity, hypertension, late-life depression, smoking, physical inactivity, diabetes, and social isolation. In this life course conceptual framework, modifications of risk factors can influence dementia decades before clinical disease onset. However, evidence "against" is supported by large randomized controlled trials (RCT, > 250 participants per arm, minimum of 6 months follow-up), primarily set to prevent dementia using lifestyle interventions that have shown modest or negative results. The 2017 National Academy of Medicine report concluded that the current evidence is limited and there are no specific interventions to warrant a public health recommendation for dementia prevention. Multiple pathological pathways are involved in the development of dementia which are theoretically treatable by managing midlife hearing loss and hypertension, and with physical exercise and education, as suggested by robust observational studies. However, evidence from large clinical trials is not conclusive to support that a third of dementia cases might be prevented. Current initiatives testing the effect of lifestyle interventions in larger clinical trials may help to settle this debate.

Non-invasive Brain Stimulation in Alzheimer's Disease and Mild Cognitive Impairment-A State-of-the-Art Review on Methodological Characteristics and Stimulation Parameters

Background: Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) have been proposed as a new therapeutic way to enhance the cognition of patients with dementia. However, serious methodological limitations appear to affect the estimates of their efficacy. We reviewed the stimulation parameters and methods of studies that used TMS or tDCS to alleviate the cognitive symptoms of patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI). Moreover, we evaluated the risk of bias in these studies. Our aim was to highlight the current vulnerabilities of the field and to formulate recommendations on how to manage these issues when designing studies. Methods: Electronic databases and citation searching were used to identify studies administering TMS or tDCS on patients with AD or MCI to enhance cognitive function. Data were extracted by one review author into summary tables with the supervision of the authors. The risk of bias analysis of randomized-controlled trials was conducted by two independent assessors with version 2 of the Cochrane risk-of-bias tool for randomized trials. Results: Overall, 36 trials were identified of which 23 randomized-controlled trials underwent a risk of bias assessment. More than 75% of randomized-controlled trials involved some levels of bias in at least one domain. Stimulation parameters were highly variable with some ranges of effectiveness emerging. Studies with low risk of bias indicated TMS to be potentially effective for patients with AD or MCI while questioned the efficacy of tDCS. Conclusions: The presence and extent of methodical issues affecting TMS and tDCS research involving patients with AD and MCI were examined for the first time. The risk of bias frequently affected the domains of the randomization process and selection of the reported data while missing outcome was rare. Unclear reporting was present involving randomization, allocation concealment, and blinding. Methodological awareness can potentially reduce the high variability of the estimates regarding the effectiveness of TMS and tDCS. Studies with low risk of bias delineate a range within TMS parameters seem to be effective but question the efficacy of tDCS.

Perioperative probiotic treatment decreased the incidence of postoperative cognitive impairment in elderly patients following non-cardiac surgery: A randomised double-blind and placebo-controlled trial

BACKGROUND

Given that population aging is a global health challenge, the high prevalence of postoperative neurocognitive impairment in elderly patients necessitates the development of novel simple and effective prevention methods.

OBJECTIVE

To evaluate the effects of perioperative application of oral probiotic as a prophylaxis for cognitive impairment in elderly patients following non-cardiac surgery.

METHODS

This randomised double-blind and placebo-controlled trial included 120 elderly patients (in a modified intention-to-treat analysis) scheduled for elective orthopaedic or colorectal surgery. Patients were assigned to receive either probiotics or a placebo from hospital admission until discharge. The primary endpoint was the incidence of postoperative cognitive impairment, defined as a decrease of ≥3 points in the Mini-Mental State Examination (MMSE) scores from admission baseline to the 7th day post-surgery. Secondary endpoints included changes in plasma interleukin-6 (IL-6) and cortisol, postoperative pain intensity, postoperative sleep quality, gastrointestinal function recovery, and faecal microbiota composition.

RESULTS

The incidence of postoperative cognitive impairment in the probiotic group was significantly lower than in the control group (3 of 59 patients [5.1%] vs. 10 of 61 patients [16.4%], P = 0.046). In addition, compared to pre-surgery, the levels of plasma IL-6 and cortisol in the probiotic group decreased more than in the control group 5-7 days after surgery (IL-6: -117.90 ± 49.15 vs. -14.93 ± 15.21, P = 0.044; cortisol: -158.70 ± 53.52 vs. 40.98 ± 72.48, P = 0.010). Relative abundance at the genus level in the faeces of the probiotic group also changed more than in that of the control group during the perioperative period. In contrast, postoperative pain intensity, sleep quality, and gastrointestinal function recovery did not differ significantly between the two groups.

CONCLUSION

Perioperative application of oral probiotic prevents postoperative cognitive impairment in elderly patients following non-cardiac surgery, possibly via the limitation of peripheral inflammation and the stress response.

Donepezil Treatment for Alzheimer's Disease in Chronic Dialysis Patients

Donepezil is one of the cholinesterase inhibitors that are indicated for the treatment of mild to moderate Alzheimer's disease (AD). Pharmacokinetic analysis has shown that donepezil is primarily eliminated by renal excretion rather than biliary excretion in humans. Therefore, patients with impaired renal function are at high risk of toxicity caused by accumulation of this drug. It is also well known that dialysis patients have very often cholinergic disorders. On the other hand, with the increasing number of long-term chronic dialysis patients, the prevalence of cognitive disorders is increasing in elderly dialysis patients. Because of the above-mentioned special risks of these patients, acetylcholinesterase inhibitors, such as donepezil, are avoided to be prescribed for them. We studied 5 cases of chronic hemodialysis outpatients (3 men [70, 72, and 86 years old] and 2 women [65 and 71 years old]) who were diagnosed as having moderate AD. We administered donepezil at 2.5 mg/day orally to the patients. After 1 month's treatment, their behavioral symptoms were improved, without them having any adverse events. We enhanced the dose to 5 mg/day without the patients experiencing any episodes of drug toxicity. After 3 months of treatment with the higher dose, their cognitive and executive functions were slightly improved and their behavioral disorders were remarkably milder, without them experiencing any episodes of drug toxicity. The patients' condition remained stable for 6 months after the initial administration of the drug. All of them were followed for the 10 following years, showing a mild cognitive decline per year for the first 5 years and more severe decline for the remaining years of the follow-up. Our cases indicate that donepezil treatment under prudent use may be well tolerated and have a beneficial impact on chronic hemodialysis patients with AD.