Comparison of various exercise interventions on cognitive function in Alzheimer's patients: A network meta-analysis

The redundant landscape of meta-analyses: Evaluating exercise interventions for older adults with cognitive impairment

BACKGROUND

Exercise to benefit cognition in older adults with cognitive impairment is well-studied. A recent proliferation of synthesis studies might be a positive contribution to the science; however, redundancy in research can be wasteful and detrimental to drawing confident conclusions about the evidence. This synthesis-based method study was designed to analyze: 1) the frequency and growth patterns of meta-analyses (MAs) and randomized controlled trials (RCTs) on this topic; and 2) the redundancy rate of the RCT studies included in MAs.

METHODS

This study was borne of a living systematic review, following standard synthesis methodology (PROSPERO registration, librarian-assisted search algorithms developed for multiple databases, searches updated regularly with most recent search in 2025). Frequency counts determined the number of RCTs and how many times they were included across the MAs.

RESULTS

Forty MAs were identified and included in the synthesis representing a total of 728 RCT studies. After reviewing RCT duplicates, 276 (37.9%) unique RCT studies comprised this body of evidence. Among these, 153 RCTs were cited in only one MA and 123 were cited in 2-19 different MAs. Thus, 452 (62.1%) of all RCTs used across the 40 MAs were redundant (i.e., represented in more than one MA).

CONCLUSIONS

This study found substantial redundancy in the RCTs used in MAs evaluating the cognitive impact of exercise for older adults with cognitive impairment. Replication is common practice in research but reliance on the same RCTs in multiple MAs creates an illusion of robustness when, in fact, the strength and diversity of the evidence may be more limited. Research redundancy is wasteful and may actually stagnate advancement of this science.

Serotonergic Regulation in Alzheimer's Disease

Serotonin (5-HT) is a neurotransmitter that also plays an important role in the regulation of vascular tone and angiogenesis. This review focuses on the involvement of the 5-HT system in pathological processes leading to the development of Alzheimer's disease (AD). There is evidence that damage or dysfunction of the 5-HT system contributes to the development of AD, and different subtypes of 5-HT receptors are a potential target for the treatment of AD. A link has been established between AD, depression, stress, and 5-HT deficiency in the brain. There are new data on the role of circadian rhythms in modulating stress, depression, and the 5-HT system; amyloid β (Aβ) plaque clearance; and AD progression. Circadian disruption inhibits Aβ plaque clearance and modulates AD progression. The properties and functions of 5-HT, its receptors, and serotonergic neurons are presented. Special attention is paid to the central role of 5-HT in brain development, including neurite outgrowth, regulation of somatic morphology, motility, synaptogenesis, control of dendritic spine shape and density, neuronal plasticity determining its role in network regeneration, and changes in innervation after brain damage. The results of different studies indicate that the interaction of amyloid β oligomers (AβO) with mitochondria is a sufficient trigger for AD-related neurodegeneration. The action of 5-HT leads to an improvement in mitochondrial quality and the restoration of brain areas after traumatic brain injury, chronic stress, or developmental disorders in AD. The role of a healthy lifestyle and drugs acting on serotonin receptors in the prevention and treatment of AD is discussed.

Comparing the impact of various exercise modalities on old adults with Alzheimer's disease: A Bayesian network meta-analysis

BACKGROUND AND PURPOSE

The global prevalence of Alzheimer's disease (AD) in the elderly is rising, and exercise is increasingly used as a non-pharmacological intervention. However, the most effective exercise modality for improving quality of life, alleviating depression, and reducing neuropsychiatric symptoms in AD patients remains unclear. This study aims to identify the optimal exercise modality for addressing these symptoms through a network meta-analysis.

METHODS

As of November 2024, we conducted a comprehensive search across six databases: PubMed, Embase, Web of Science, the Cochrane Central Register of Controlled Trials, CINAHL, and PsycINFO. This study included only randomized controlled trials (RCTs), with study durations ranging from 2 to 24 weeks, primarily set in clinical or community environments. Following the PRISMA-NMA guidelines, we conducted statistical analysis using the "gemtc" package in R and assessed evidence quality via the CINeMA online platform.

RESULTS

A network meta-analysis of 29 RCTs with 1507 participants showed that for global cognition, Aerobic exercise (AE) [MD = 2.83, 95 % CI (0.66, 4.85)] ranked first with 79.5 % probability; for quality of daily life, Resistance Training (RT) [SMD = 0.96, 95 % CI (-0.14, 2.07)] ranked first with 83.7 %; for depression, Physical Activity Program (PAP) [SMD = -3.76, 95 % CI (-7.06, -0.47)] ranked first with 96.0 %; and for neuropsychiatric inventory outcomes, AE [SMD = -2.35, 95 % CI (-5.95, 1.06)] ranked first with 71.1 %.

CONCLUSIONS

Based on the findings from retrospective studies, aerobic exercise may be an effective intervention for improving overall cognition and quality of life in individuals aged 60 and above with Alzheimer's disease.

Meta-analysis of the effects of multi-component exercise on cognitive function in older adults with cognitive impairment

Exercise has been widely recognized as an effective regimen in mitigating cognitive decline. However, the effect of multi-component exercise (i.e., combination of two or more types of exercise) on cognitive function and its subdomains in older adults remains unclear. This meta-analysis aimed to explore the effects of multi-component exercise on cognitive functions in elderly individuals with cognitive impairment and identify optimal prevention and treatment strategies. A systematic search was conducted on PubMed, EBSCOhost, Web of Science, and Embase to identify relevant randomized controlled trials assessing the effect of multi-component exercise on cognitive function in the elderly. Thirteen studies with 1,776 participants were included in the analysis using Revman 5.4 software. The results showed that multi-component exercise had a significant effect on mitigating cognitive function decline in the elderly, with a pooled effect size of SMD = 0.31 (95% CI: 0.08, 0.55; p = 0.009). The results of subgroup analysis showed that interventions with ≥3 days/week, 12-24 weeks duration, and ≤ 40 min/session were significantly superior to other frequencies, durations, and lengths, with all p-values <0.05. Additionally, multi-component exercise had the most pronounced effects on executive function, visual memory, and verbal memory in patients with mild cognitive impairment (MCI). In conclusion, multi-component exercise can delay the decline in cognitive function in the elderly, and the intervention effects are modulated by various variables. Optimal intervention effects were observed with an exercise frequency of three or more times per week, a duration of 12 to 24 weeks, and a time per session of 40 min or less, particularly for improving executive function, visual memory, and verbal memory in patients with MCI.

Mapping the scientific research on exercise therapy for Alzheimer's disease: a scientometric study of hotspots and emerging trends

Background

Alzheimer's disease (AD) is the most common form of dementia globally, placing a substantial economic burden on patients and society. Exercise serves as an adjuvant therapy for AD with a low incidence of related adverse events. As a non-pharmacological intervention, it has demonstrated significant potential in the therapy of AD.

Objective

This study examines the key hotspots and emerging trends in exercise therapy for AD, offering valuable insights for researchers engaged in future research in this field.

Methods

The Web of Science Core Collection database was utilized to search for literature on exercise therapy for AD from January 1, 2000, to November 1, 2024, with 1,372 relevant articles being identified. And CiteSpace 6.2.R4 and VOSviewer were used to evaluate the bibliometric indicators.

Results

Since 2000, the number of publications in the field of exercise therapy for AD has been increasing. In addition to the well-known areas of research, such as the impact of exercise on cognitive function, the combination of exercise and medication therapy, the effects of exercise on specific symptoms, and the exercise with music therapy, the field may also focus on more novel topics. These include the integration of the design and implementation of exercise interventions, exercise and dendritic spines, and exercise and neurophysiological mechanisms. Furthermore, an analysis of emerging keywords reveals that the current main research direction is exploring the specific physiological mechanisms through which exercise affects AD. This includes three emerging trends: the impact of exercise on cognitive impairment in AD patients, the effects of exercise on brain-derived neurotrophic factor (BDNF) and Amyloid beta, and the influence of exercise on Stress and neuroinflammation.

Conclusion

The research results indicate that interventions using exercise to alleviate the negative symptoms of AD, as well as combining exercise with medication for therapy, are gaining increasing attention from researchers. Meanwhile, novel topics such as exercise and music therapy, the design and implementation of exercise interventions, and neurophysiological mechanisms should also attract scholarly interest. Additionally, exploring the physiological mechanisms behind exercise therapy for AD could be a key focus for future research.

A review of the application of exercise intervention on improving cognition in patients with Alzheimer's disease: mechanisms and clinical studies

Alzheimer's disease (AD) is the most common form of dementia, leading to sustained cognitive decline. An increasing number of studies suggest that exercise is an effective strategy to promote the improvement of cognition in AD. Mechanisms of the benefits of exercise intervention on cognitive function may include modulation of vascular factors by affecting cardiovascular risk factors, regulating cardiorespiratory health, and enhancing cerebral blood flow. Exercise also promotes neurogenesis by stimulating neurotrophic factors, affecting neuroplasticity in the brain. Additionally, regular exercise improves the neuropathological characteristics of AD by improving mitochondrial function, and the brain redox status. More and more attention has been paid to the effect of Aβ and tau pathology as well as sleep disorders on cognitive function in persons diagnosed with AD. Besides, there are various forms of exercise intervention in cognitive improvement in patients with AD, including aerobic exercise, resistance exercise, and multi-component exercise. Consequently, the purpose of this review is to summarize the findings of the mechanisms of exercise intervention on cognitive function in patients with AD, and also discuss the application of different exercise interventions in cognitive impairment in AD to provide a theoretical basis and reference for the selection of exercise intervention in cognitive rehabilitation in AD.

Different physical exercise in the treatment of Alzheimer's disease

Alzheimer's disease (AD) is rapidly becoming one of the most expensive, burdening, and deadly diseases of this century. Up to now, there is still a lack of pharmacotherapy with substantial efficacy, and physical exercise is a promising and low-cost way to aid in delaying the process of AD. The aim of this review is to summarise the efficacy of different physical exercise approaches and doses in the management of AD, including aerobic exercise, resistance exercise and multicomponent exercise. A literature search using MeSH terms for each topic is undertaken using PubMed and the Web of Science Core Collection database, supplemented by hand searching for additional references. Retrieved articles were reviewed, synthesised, and summarised. This review shows that aerobic exercise has been almost unanimously recognised for the improvement of cognition, neuropsychiatric symptoms and activities of daily living. Resistance exercise also shows a good prospect in the above aspects and has a unique advantage in enhancing muscle strength, while multicomponent physical activity does not seen to significantly improve cognitive function. Each type of exercise has a dose effect, but for individuals with AD, the most appropriate exercise dose is still controversial.

Effects of non-pharmacological interventions for adults with subjective cognitive decline: a network meta-analysis and component network meta-analysis

BACKGROUND

Non-pharmacological interventions have a myriad of available intervention options and contain multiple components. Whether specific components of non-pharmacological interventions or combinations are superior to others remains unclear. The main aim of this study is to compare the effects of different combinations of non-pharmacological interventions and their specific components on health-related outcomes in adults with subjective cognitive decline.

METHODS

PubMed, Embase, Cochrane, CINAHL, PsycINFO, CENTRAL, Web of Science, and China's two largest databases, CNKI and Wanfang, were searched from inception to 22nd, January 2023. Randomized controlled trials using non-pharmacological interventions and reporting health outcomes in adults with subjective cognitive decline were included. Two independent reviewers screened studies, extracted data, and assessed risk of bias. Component network meta-analysis was conducted employing an additive component model for network meta-analysis. This study followed the PRISMA reporting guideline and the PRISMA checklist is presented in Additional file 2.

RESULTS

A total of 39 trials with 2959 patients were included (range of mean ages, 58.79-77.41 years). Resistance exercise might be the optimal intervention for reducing memory complaints in adults with subjective cognitive decline; the surface under the cumulative ranking p score was 0.888, followed by balance exercise (p = 0.859), aerobic exercise (p = 0.832), and cognitive interventions (p = 0.618). Music therapy, cognitive training, transcranial direct current stimulation, mindfulness therapy, and balance exercises might be the most effective intervention components for improving global cognitive function (iSMD, 0.83; 95% CI, 0.36 to 1.29), language (iSMD, 0.31; 95% CI, 0.24 to 0.38), ability to perform activities of daily living (iSMD, 0.55; 95% CI, 0.21 to 0.89), physical health (iSMD, 3.29; 95% CI, 2.57 to 4.00), and anxiety relief (iSMD, 0.71; 95% CI, 0.26 to 1.16), respectively.

CONCLUSIONS

The form of physical activity performed appears to be more beneficial than cognitive interventions in reducing subjective memory complaints for adults with subjective cognitive decline, and this difference was reflected in resistance, aerobic, and balance exercises. Randomized clinical trials with high-quality and large-scale are warranted to validate the findings.

TRIAL REGISTRATION

PROSPERO registry number. CRD42022355363.

Effective dosage and mode of exercise for enhancing cognitive function in Alzheimer's disease and dementia: a systematic review and Bayesian Model-Based Network Meta-analysis of RCTs

OBJECTIVE

Research the dose-response relationship between overall and certain types of exercise and cognitive function in older adults with Alzheimer's disease and dementia.

DESIGN

Systemic and Bayesian Model-Based Network Meta-Analysis.

METHODS

In our study, we analyzed data from randomized controlled trials investigating the effects of different exercises on cognitive outcomes in older adults with AD. We searched the Web of Science, PubMed, Cochrane Central Register of Controlled Trials, and Embase up to November 2023. Using the Cochrane Risk of Bias tool (Rob2) for quality assessment and R software with the MBNMA package for data analysis, we determined standard mean differences (SMDs) and 95% confidence intervals (95%CrI) to evaluate exercise's impact on cognitive function in AD.

RESULTS

Twenty-seven studies with 2,242 AD patients revealed a nonlinear relationship between exercise and cognitive improvement in AD patients. We observed significant cognitive enhancements at an effective exercise dose of up to 1000 METs-min/week (SMDs: 0.535, SD: 0.269, 95% CrI: 0.023 to 1.092). The optimal dose was found to be 650 METs-min/week (SMDs: 0.691, SD: 0.169, 95% CrI: 0.373 to 1.039), with AE (Aerobic exercise) being particularly effective. For AE, the optimal cognitive enhancement dose was determined to be 660 METs-min/week (SMDs: 0.909, SD: 0.219, 95% CrI: 0.495 to 1.362).

CONCLUSION

Nonlinear dose-response relationship between exercise and cognitive improvement in Alzheimer's disease, with the optimal AE dose identified at 660 METs-min/week for enhancing cognitive function in AD.

Multidomain interventions for sarcopenia and cognitive flexibility in older adults for promoting healthy aging: a systematic review and meta-analysis of randomized controlled trials

The global population is undergoing rapid aging, making physical activity a crucial element in preventing mortality and lowering the risk of Alzheimer's disease. Age-related declines in muscle mass and cognitive abilities significantly contribute to frailty and dependency. Thus, this study focuses on a meticulous analysis of the protective effects of multidomain interventions, an emerging resource combating age-related declines. It seeks to underscore their profound impact on cognitive flexibility and sarcopenia, highlighting their pivotal role in mitigating the adverse effects of aging. To identify relevant randomized controlled trials up to November 2023, we reviewed eight online academic databases, following PERSiST guidelines, PRISMA reporting system, and PICOs criteria. Meta-analyses on selected functional outcomes utilized a random-effects model, including the Timed Up and Go Test, Sit to Stand Test, Victoria Stroop Test, and Trail Making Test. Out of 2082 scrutinized articles, 17 were included in the systematic review, and 8 in the meta-analysis. Positive effects (p = 0.05, I2 = 57%; 95% CI - 0.63 to - 0.05) were observed in cognitive flexibility for certain interventions. Similarly, interventions addressing muscle strength demonstrated improvements in the Sit to Stand Test for the exercise group compared to the control group (p = 0.02, I2 = 0%; 95% CI - 0.63 to - 0.05). These findings underscore the importance of incorporating physical activity as a primary component of public health interventions for promoting healthy aging and reducing the burden of age-related diseases. Future interventions may explore more homogeneous approaches and evaluate the impact of thrice multidomain weekly sessions.

Exercise Intervention for Alzheimer's Disease: Unraveling Neurobiological Mechanisms and Assessing Effects

Alzheimer's disease (AD) is a progressive neurodegenerative disease and a major cause of age-related dementia, characterized by cognitive dysfunction and memory impairment. The underlying causes include the accumulation of beta-amyloid protein (Aβ) in the brain, abnormal phosphorylation, and aggregation of tau protein within nerve cells, as well as neuronal damage and death. Currently, there is no cure for AD with drug therapy. Non-pharmacological interventions such as exercise have been widely used to treat AD, but the specific molecular and biological mechanisms are not well understood. In this narrative review, we integrate the biology of AD and summarize the knowledge of the molecular, neural, and physiological mechanisms underlying exercise-induced improvements in AD progression. We discuss various exercise interventions used in AD and show that exercise directly or indirectly affects the brain by regulating crosstalk mechanisms between peripheral organs and the brain, including "bone-brain crosstalk", "muscle-brain crosstalk", and "gut-brain crosstalk". We also summarize the potential role of artificial intelligence and neuroimaging technologies in exercise interventions for AD. We emphasize that moderate-intensity, regular, long-term exercise may improve the progression of Alzheimer's disease through various molecular and biological pathways, with multimodal exercise providing greater benefits. Through in-depth exploration of the molecular and biological mechanisms and effects of exercise interventions in improving AD progression, this review aims to contribute to the existing knowledge base and provide insights into new therapeutic strategies for managing AD.