Alzheimer Disease Therapeutics: Perspectives from the Developing World

Transcranial pulse stimulation in Alzheimer's disease

BACKGROUND

Transcranial pulse stimulation (TPS) is a novel noninvasive ultrasonic brain stimulation that can increase cortical and corticospinal excitability, induce neuroplasticity, and increase functional connectivity within the brain. Several trials have confirmed its potential in treating Alzheimer's disease (AD).

OBJECTIVE

To investigate the effect and safety of TPS on AD.

DESIGN

A systematic review.

METHODS

PubMed, Embase via Ovid, Web of Science, Cochrane Library, CNKI (China National Knowledge Infrastructure), VIP (China Science and Technology Journal Database), and WanFang were searched from inception to April 1, 2023. Study selection, data extraction, and quality evaluation of the studies were conducted by two reviewers independently, with any controversy resolved by consensus. The Methodological Index for Nonrandomized Studies was used to assess the risk of bias.

RESULTS

Five studies were included in this review, with a total of 99 patients with AD. For cognitive performance, TPS significantly improved the scores of the CERAD (Consortium to Establish a Registry for Alzheimer's Disease) test battery, Alzheimer's Disease Assessment Scale (cognitive), Montreal Cognitive Assessment, and Mini-Mental Status Examination. For depressive symptoms, TPS significantly reduced the scores of the Alzheimer's Disease Assessment Scale (affective), Geriatric Depression Score, and Beck Depression Inventory. By functional magnetic resonance imaging, studies have shown that TPS improved cognitive performance in AD patients by increasing functional connectivity in the hippocampus, parahippocampal cortex, precuneus, and parietal cortex, and activating cortical activity in the bilateral hippocampus. TPS alleviated depressive symptoms in AD patients by decreasing functional connectivity between the ventromedial network (left frontal orbital cortex) and the salience network (right anterior insula). Adverse events in this review, including headache, worsening mood, jaw pain, nausea, and drowsiness, were reversible and lasted no longer than 1 day. No serious adverse events or complications were observed.

CONCLUSIONS

TPS is promising in improving cognitive performance and reducing depressive symptoms in patients with AD. TPS may be a safe adjunct therapy in the treatment of AD. However, these findings lacked a sham control and were limited by the small sample size of the included studies. Further research may be needed to better explore the potential of TPS.

PATIENT AND PUBLIC INVOLVEMENT

Patients and the public were not involved in this study.

Efficacy analysis of three brain stimulation techniques for Alzheimer's disease: a meta-analysis of repeated transcranial magnetic stimulation, transcranial direct current stimulation, and deep brain stimulation

INTRODUCTION

This systematic review and meta-analysis study investigates the efficacy of repeated transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), and deep brain stimulation (DBS) using neuropsychological assessments as a potential treatment option for Alzheimer's disease (AD).

METHODS

PubMed, Embase, and the Cochrane Library were searched for studies on rTMS, tDCS, and DBS for the treatment of patients with AD between April 1970 and October 2022. The mini-Mental State Examination (MMSE) and AD Assessment Scale - Cognitive Subscale (ADAS-Cog) were adopted as the efficacy index.

RESULTS

The analysis yielded 17 eligible studies. rTMS greatly improved the cognition of patients with AD (immediate post-treatment WMD of MMSE score: 2.06, p < 0.00001; short-term follow-up WMD of MMSE score: 2.12, p = 0.006; WMD of ADAS-Cog score in single-arm studies: -4.97, p = 0.001). DBS did not reverse the progression of cognitive decline (WMD of ADAS-Cog score in single-arm studies: 7.40, p < 0.00001). Furthermore, tDCS demonstrated no significant efficacy in improving cognition in random clinical trials or single-arm studies.

CONCLUSION

rTMS is a promising non-medicinal alternative for cognitive improvement inpatients with AD.

A Survey of Mobile Apps for the Care Management of Patients with Dementia

Objective: Dementia is a progressive neurocognitive disorder that currently affects approximately 50 million people globally and causes a heavy burden for their families and societies. This study analyzed mobile apps for dementia care in different languages and during the COVID-19 pandemic. Methods: We searched PubMed, Cochrane Collaboration Central Register of Con-trolled Clinical Trials, Cochrane Systematic Reviews, Google Play Store, Apple App Store, and Huawei App Store for mobile applications for dementia care. The Mobile Application Rating Scale (MARS) was used to assess the quality of applications. Results: We included 99 apps for dementia care. No significant difference in MARS scores was noted between the two language apps (Overall MARS: English: 3.576 ± 0.580, Chinese: 3.569 ± 0.746, p = 0.962). In the subscale analysis, English apps had higher scores of perceived impact than Chinese apps but these were not significant (2.654 ± 1.372 vs. 2.000 ± 1.057, p = 0.061). (2) Applications during the COVID-19 pandemic had higher MARS scores than those before the COVID-19 pandemic but these were not significant (during the COVID-19 pandemic: 3.722 ± 0.416; before: 3.699 ± 0.615, p = 0.299). In the sub-scale analysis, apps during the COVID-19 pandemic had higher scores of engagement than apps before the COVID-19 pandemic but these were not significant (3.117 ± 0.594 vs. 2.698 ± 0.716, p = 0.068). Conclusions: Our results revealed that there is a minor but nonsignificant difference between different languages and during the COVID-19 pandemic. Further cooperation among dementia professionals, technology experts, and caregivers is warranted to provide evidence-based and user-friendly information to meet the needs of users.

Effect of N-methyl-D-aspartate receptor enhancing agents on cognition in dementia: an exploratory systematic review and meta-analysis of randomized controlled trials

Multiple N-methyl-D-aspartate (NMDA) receptor enhancing agents have had promising effects on cognition among patients with dementia. However, the results remain inconsistent. This exploratory meta-analysis investigated the effectiveness of NMDA receptor enhancing agents for cognitive function. PubMed, the Cochrane Central Register of Controlled Trials, and the Cochrane Database of Systematic Reviews were searched for randomized controlled trials (RCTs). Controlled trials assessing add-on NMDA receptor enhancing agent treatment in patients with dementia and using cognition rating scales were eligible and pooled using a random-effect model for comparisons. The standardized mean difference (SMD) was calculated in each study from the effect size; positive values indicated that NMDA receptor enhancing agent treatment improved cognitive function. Funnel plots and the I2 statistic were evaluated for statistical heterogeneity. Moderators were evaluated using meta-regression. We identified 14 RCTs with 2224 participants meeting the inclusion criteria. Add-on NMDA receptor enhancing agents had small positive significant effects on overall cognitive function among patients with dementia (SMD = 0.1002, 95% CI 0.0105-0.1900, P = 0.02860). Subgroup meta-analysis showed patients with Alzheimer's Disease and trials using the Alzheimer Disease Assessment Scale-cognitive subscale as the primary outcome had small positive significant effects (SMD = 0.1042, 95% CI 0.0076-0.2007, P = 0.03451; SMD = 0.1267, 95% CI 0.0145-0.2388, P = 0.2686). This exploratory meta-analysis showed a very small, positive, and significant effect on overall cognition function in patients with dementia. Studies with larger samples are needed to evaluate different cognitive domains and phases of dementia.

Dementia awareness, beliefs and barriers among family caregivers in Pakistan

OBJECTIVES

Dementia research and services in Pakistan are limited. The following was explored in experiences of family caregivers of people with dementia in Pakistan: (a) to determine whether culture and religion play a role in caregiving; (b) to draw insights on how family caregivers cope, what barriers they face and what help they would be willing to accept and (c) to determine how these findings could be used to raise awareness and influence public policies in improving the lives of families living with dementia.

METHODS

The experiences of family caregivers of people with dementia in Pakistan were explored via semi-structured interviews (10 in Lahore; 10 in Karachi). This was part of a larger qualitative study conducted about dementia in Pakistan. Caregivers interviewed were aged 35-80 (14 female). Most caregivers in the study were educated and affluent. Interviews were conducted in Urdu, translated into English and thematically analysed.

RESULTS

Five themes emerged: knowledge and awareness; stigma; importance of religion and duty to care; use of day care centres and home-help; and barriers. A lack of dementia awareness exists in Pakistan. The religious duty to care for family influenced caregiving decisions. Day care centres and home-help were accessed and viewed positively. The caregivers also wanted extracurricular activities for people with dementia, support groups for caregivers and better training for healthcare staff. Novel findings included that caregivers felt that dementia should not be stigmatised, and awareness should be raised in Pakistan via TV, radio and social media, but not inside mosques.

DISCUSSION

Additional research is necessary to determine if positive views of day care centres and home-help exist more widely. Attitudes and experiences regarding stigma may be different for caregivers of people with more advanced dementia. We recommend raising dementia awareness, allocating more funds to dementia services and an emphasis on home-based care.

Repetitive transcranial magnetic stimulation for cognitive impairment in Alzheimer's disease: a meta-analysis of randomized controlled trials

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive brain stimulation technique for Alzheimer's disease (AD). rTMS, with high- or low-frequency, is thought to enhance or inhibit the cortical activities, respectively. This meta-analysis of randomized controlled trials (RCTs) was to summarize the efficacy of the rTMS on the cognition of AD patients and to identify its potential influential factors.

METHODS

Literature from the Pubmed, Embase, Cochrane Library and Web of Science were searched and screened to identify eligible studies. Standardized mean difference (SMD) and 95% confidence interval were used to evaluate the therapeutic effects of rTMS. Subgroup analyses were performed to investigate the influential factors.

RESULTS

Ten studies with 15 trials involving 240 patients were included. Compared with sham stimulation, rTMS could significantly improve cognition in AD (SMD, 0.42; 95% CI 0.18-0.67; P = 0.0006). Subgroup analysis suggested significant cognitive enhancement in participants receiving rTMS on multiple sites rather than on single site, and in patients receiving rTMS of more than 10 sessions, but not ≤ 10 sessions. Compared with rTMS as the single therapeutic method, rTMS with concurrent cognitive training seemed to produce greater improvement. Moreover, 20 Hz rTMS, seemed to be more effective than 10 Hz or 1 Hz rTMS. Furthermore, patients with higher education, or with mild-to-moderate AD were more likely to benefit from rTMS than patients with lower education, or with severe dementia, respectively.

CONCLUSIONS

Based on the current evidence, rTMS was an effective therapy for cognitive impairment in AD. Large RCTs are warranted to further validate the results of our subgroup analyses.

Current status and potential role of circular RNAs in neurological disorders

Given the importance of non-coding RNAs in modulating normal brain functions and their implications in the treatment of neurological disorders, non-coding RNA-based diagnostic and therapeutic strategies have shown great clinical potential. Circular RNAs (circRNAs) have emerged as potentially important players in this field. Recent studies have indicated that circRNAs might play vital roles in Alzheimer's disease, Parkinson's disease, ischemic brain injury, and neurotoxicity. However, the mechanisms of action of circRNAs have not been fully characterized. We aimed to review recent advances in circRNA research in the brain to provide new insights on the roles of circRNAs in neurological disorders.

Brain Stimulation in Alzheimer's Disease

Brain stimulation techniques can modulate cognitive functions in many neuropsychiatric diseases. Pilot studies have shown promising effects of brain stimulations on Alzheimer's disease (AD). Brain stimulations can be categorized into non-invasive brain stimulation (NIBS) and invasive brain stimulation (IBS). IBS includes deep brain stimulation (DBS), and invasive vagus nerve stimulation (VNS), whereas NIBS includes transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), transcranial alternating current stimulation (tACS), electroconvulsive treatment (ECT), magnetic seizure therapy (MST), cranial electrostimulation (CES), and non-invasive VNS. We reviewed the cutting-edge research on these brain stimulation techniques and discussed their therapeutic effects on AD. Both IBS and NIBS may have potential to be developed as novel treatments for AD; however, mixed findings may result from different study designs, patients selection, population, or samples sizes. Therefore, the efficacy of NIBS and IBS in AD remains uncertain, and needs to be further investigated. Moreover, more standardized study designs with larger sample sizes and longitudinal follow-up are warranted for establishing a structural guide for future studies and clinical application.

No Significant Effect of Prefrontal tDCS on Working Memory Performance in Older Adults

Transcranial direct current stimulation (tDCS) has been put forward as a non-pharmacological alternative for alleviating cognitive decline in old age. Although results have shown some promise, little is known about the optimal stimulation parameters for modulation in the cognitive domain. In this study, the effects of tDCS over the dorsolateral prefrontal cortex (dlPFC) on working memory performance were investigated in thirty older adults. An N-back task assessed working memory before, during and after anodal tDCS at a current strength of 1 mA and 2 mA, in addition to sham stimulation. The study used a single-blind, cross-over design. The results revealed no significant effect of tDCS on accuracy or response times during or after stimulation, for any of the current strengths. These results suggest that a single session of tDCS over the dlPFC is unlikely to improve working memory, as assessed by an N-back task, in old age.

Effects of noninvasive brain stimulation on cognitive function in healthy aging and Alzheimer's disease: a systematic review and meta-analysis

The study aimed to evaluate the effects of noninvasive brain stimulation on cognitive function in healthy older adults and patients with Alzheimer's disease. A comprehensive literature search was performed on noninvasive stimulation studies published from January 1990 to November 2014 in Pubmed and Web of Science. Fourteen articles with a total of 331 participants were identified as studies with healthy older adults, and the mean effect size and 95% confidence interval were estimated. A significant effect size of 0.42 was found for the cognitive outcome. Further subgroup analyses demonstrated more prominent effects for studies delivering the stimulation before the execution of the task and studies applying multiple sessions of stimulation. To assess the effects of stimulation on Alzheimer's disease patients, 11 studies with a total of 200 patients were included in the analysis. A significant effect size of 1.35 was found for the cognitive outcomes. Subgroup analyses indicated more pronounced effects for studies applying the stimulation during the execution of the task compared with studies delivering the stimulation before the execution of the task. Noninvasive brain stimulation has a positive effect on cognitive function in physiological and pathological aging.

Prolonged visual memory enhancement after direct current stimulation in Alzheimer's disease

BACKGROUND

Immediately after patients with Alzheimer's disease (AD) receive a single anodal transcranial direct current stimulation (tDCS) session their memory performance improves. Whether multiple tDCS sessions improve memory performance in the longer term remains unclear.

OBJECTIVE

In this study we aimed to assess memory changes after five consecutive sessions of anodal tDCS applied over the temporal cortex in patients with AD.

METHODS

A total of 15 patients were enrolled in two centers. Cognitive functions were evaluated before and after therapeutic tDCS. tDCS was delivered bilaterally through two scalp anodal electrodes placed over the temporal regions and a reference electrode over the right deltoid muscle. The stimulating current was set at 2 mA intensity and was delivered for 30 minutes per day for 5 consecutive days.

RESULTS

After patients received tDCS, their performance in a visual recognition memory test significantly improved. We found a main effect of tDCS on memory performance, i.e., anodal stimulation improved it by 8.99% from baseline, whereas sham stimulation decreased it by 2.62%. tDCS failed to influence differentially general cognitive performance measures or a visual attention measure.

CONCLUSIONS

Our findings show that after patients with AD receive anodal tDCS over the temporal cerebral cortex in five consecutive daily sessions their visual recognition memory improves and the improvement persists for at least 4 weeks after therapy. These encouraging results provide additional support for continuing to investigate anodal tDCS as an adjuvant treatment for patients with AD.

Conceptual evolution in Alzheimer's disease: implications for understanding the clinical phenotype of progressive neurodegenerative disease

Over the past several decades, our understanding of Alzheimer's disease (AD) has seen an evolution from the dichotomous concept of normal versus AD in the dementia state to a more accurate and complete appreciation of AD as a progressive disorder with clinical, biological, and pathological features occurring along a continuum from normal to end-stage disease. Integrating our understanding of the relationships and interplay between the clinical, biological, and pathological features of AD may allow the identification of AD at even preclinical, completely asymptomatic stages of the disease. This review attempts to summarize the clinical stages of AD in terms of epidemiology, historical evolution of disease stage diagnoses, cognitive/neuropsychologic features, psychiatric/behavioral manifestations, and functional decline in the context of our developing understanding of the biological processes responsible for the pathogenesis of AD described in detail in the accompanying articles.

Clinical practice with antidementia and antipsychotic drugs: Audit from a geriatric clinic in India

BACKGROUND

Dementia is one of the most disabling disorders afflicting the elderly, with a staggering emotional and economic impact. Antidementia agents have been used for delaying cognitive decline. Antipsychotics are commonly prescribed for behavioral symptoms associated with dementia.

OBJECTIVES

To explore the use of anti-dementing agents and antipsychotics used in patients with a diagnosis of dementia Materials and Methods: A retrospective chart review method; geriatric clinic of tertiary care setting.

RESULTS

The study sample included 51 consecutive patients with a diagnosis of dementia. The commonest subtype of dementia that was diagnosed was Alzheimer's disease (45%), followed by Frontotemporal dementia (25%).The commonest antidementia drug that was used was donepezil, which alone was prescribed in 27 patients (52%). The commonest antipsychotic used was quetiapine, which was used in 24 patients (47%).

CONCLUSIONS

The study found donepezil to be the most commonly prescribed antidementia drug and quetiapine to be the most commonly used antipsychotic in a tertiary care geriatric clinic, in a developing country. There is a need to study the cost-effectiveness of antidementia and antipsychotic drugs in patients with dementia, in developing countries.