Introduction

Mild cognitive impairment (MCI) can but does not have to be a transitional state of cognitive function between normal ageing and dementia.1 2 The prevalence of MCI in Chinese older adults over the age of 60 was reported to be 20.8%, and the overall global prevalence of MCI was 19.7% in 2023.3 Approximately 10%–15% of individuals with MCI progress to dementia, with approximately 80% progressing to Alzheimer’s disease (AD) after 6 years of follow-up,4 exacerbating concerns for the reduced social and functional capacity of these individuals and their increased disease burden.5 6 However, the appropriate interventions can improve cognitive function in MCI, delaying its pathological progression and even resorting it to normal.7

Regular exercise training or physical activity has been identified as a means to improve cognitive performance in community-dwelling older adults with MCI.8 However, conventional aerobic or resistance exercise may also present mobility and movement challenges that limit the accessibility of the intervention to all older adults. Unlike conventional aerobic or resistance exercise types that focus only on strengthening the physical body, Baduanjin exercise, a traditional Chinese mind-body exercise, especially emphasises the integration of body postures, movements, meditation and breathing to cultivate qi (vital energy based on the theory of traditional Chinese medicine) with the characteristics of the gentle movements, breathing techniques and meditation.9 10 Unlike aerobic or resistance exercises, Baduanjin does not require significant physical strength, dynamic balance or extensive mobility, making it more accessible for older adults, even those with limited physical capacity. It, therefore, is safe with mild to moderate intensity and is recommended as an appropriate type of exercise for the elderly population.11 A growing body of research has shown that it can improve cognitive function in older adults with MCI.12–14

The human gut microbiota, a complex community of bacterial-dominated microbes, plays an important role in modulating metabolic, immune, psychological and cognitive functions of the host.15 Recent evidence suggests a clear link between the gut microbiota and cognitive function, known as the microbiome–gut–brain axis (MGBA).16 Since the gut microbiota ecosystem is dynamic, it is constantly changing throughout the lifespan. With ageing, reduced microbial diversity may contribute to gut dysbiosis,17 which can negatively impact brain function through the MGBA mechanisms such as neuroinflammation, neurotoxicity and oxidative stress.18 Studies have shown that changes in the microbiota in patients with cognitive impairment and AD are associated with disease severity and are generally characterised by an increase in Gram-negative microorganisms in the Bacteroidetes and Proteobacteria phyla and a decrease in Gram-positive microorganisms in the Firmicutes and Actinobacteria phyla. This leads to increased release of lipopolysaccharides, which disrupts the integrity of the intestinal mucosal barrier and initiates neuroinflammation,19 suggesting that gut dysbiosis is an important pathophysiological mechanism of MCI. Moreover, regular exercise training is a modulator of gut microbiota composition and diversity. Several systematic reviews of observational and interventional studies in community-dwelling populations indicate that regular exercise training has beneficial effects on gut microbiota diversity, with increases in certain bacteria that produce beneficial metabolites such as short-chain fatty acids (SCFAs) and some neurotransmitters.20 Recent studies have also shown that exercise-induced changes in the gut microbiota may activate the gut–muscle–brain axis with improved cognitive function.21 22 Although several studies have examined the effects of Baduanjin exercise on the gut microbiome,23 24 the role of the gut microbiome in the protective effects of Baduanjin exercise on cognition in older adults is unclear. Furthermore, a better understanding of the role of the gut microbiome in the effects of Baduanjin exercise on cognition may help to optimise these lifestyle interventions. Therefore, we will conduct a randomised controlled trial to evaluate the potential effects of gut microbiota and its metabolites in the Baduanjin impact on cognitive function in community-dwelling MCI older adults.

Study hypotheses and objectivesStudy hypotheses

The study hypothesises that 24 weeks of supervised Baduanjin exercise training in community-dwelling older adults with MCI has beneficial effects on cognitive function such as global cognitive ability or the specific subdimension of cognition, and the beneficial effects of Baduanjin exercise on cognition in the MCI older adults are mediated by the gut microbiota and its metabolites involved in the gut–brain axis (figure 1).

Figure 1

The proposed chain mediation model. Hypotheses of gut microbiota mediating Baduanjin training impact on cognition: hypothesis 1: Baduanjin exercise training can improve cognitive function (eg, global cognitive ability and its sub-dimensions) and gut microecology (eg, gut microbiota and its metabolites) in community-dwelling older adults with MCI; hypothesis 2: the improved gut microecology can indirectly cause the improvement of cognitive function in community-dwelling older adults with MCI. MCI, mild cognitive impairment.

Study objectives

Objective 1: to investigate the effects of 24 weeks of supervised Baduanjin exercise training on cognitive function, including global cognitive ability and its subdimension, in community-dwelling older adults with MCI.

Objective 2: to investigate how the gut microbiota and its metabolites mediate the effects of Baduanjin exercise on cognition.

Methods and analysisStudy design

This is a two-arm, randomised, parallel-controlled, single-blind trial (figure 2). Eligible participants will be randomly assigned to either the 24-week Baduanjin exercise intervention group or the no specific exercise intervention control group. This trial has been prospectively registered at Chictr.org.cn with registration number ChiCTR2300078147 on 29 November 2023. The study protocol was approved by the Ethics Committee of the Shanghai University of Medicine and Health Sciences in accordance with the Declaration of Helsinki. The study design adhered to the guidelines of the Standard Protocol Items: Recommendations for Interventional Trials 2013 guidelines.25 The study procedures and timeline for outcome assessment for this trial are shown in figure 2. Enrolled participants will provide written informed consent prior to participation.

Figure 2

Study design of this randomised controlled trial. MCI, mild cognitive impairment.

Sample size calculation

Given the lack of information to assess the effect of the gut microbiome-mediated Baduanjin exercise intervention on cognitive function in older adults, sample size calculation focused on the primary outcome (global cognitive ability). Based on our previous work,12 we calculated, using sample size software (Gpower V.3.1.97), that a total sample size of 27 participants would be necessary to detect the previously found effect (Cohen’s d=0.79) of the 24-week Baduanjin exercise intervention on the global cognitive ability with 80% power and an alpha level of 0.05. Considering a 20% of attrition rate,9 we aim to recruit a total of 64 participants (n=32 per group).

Study population

The study population is community-dwelling older adults with MCI. The diagnostic, inclusion and exclusion criteria for the study sample are as follows. Screening of participants for eligibility criteria, including assessment of MCI, inclusion and exclusion criteria, will be conducted by the trained postgraduate students during the recruitment phase. Subjective and objective cognitive impairments will be assessed through the fact-to-face interview or the Montreal Cognitive Assessment (MoCA) scale; normal activities of daily living and dementia will be examined using the Lawton-Brody ADL tool and the Global Deterioration Scale (GDS) scale. Inclusion and exclusion conditions will be assessed using a self-designed screening questionnaire.

Diagnostic criteria

According to the Peterson criteria for MCI,26 the MCI participants should have (1) cognitive impairment complaints or cognitive impairment manifestations confirmed by informed persons (face-to-face interview during recruitment); (2) objective evidence of cognitive decline in at least one cognitive domain (MoCA score ≤26 and adjustment for the education level); (3) maintenance of normal activities of daily living (Lawton–Brody ADL score ≤18); (4) absence of dementia (GDS score of 2 or 3 levels).

Inclusion criteria

Eligible participants should meet the following criteria:

(1) Community-dwelling older adults aged 60 years or older; (2) meeting the MCI criteria; (3) no regular physical exercise in the past 6 months (regular exercise is defined as a frequency of at least three sessions per week and at least 20 min per session); (4) stable dietary structure (Chinese Healthy Eating Index≥60 points); (5) informed consent.

Exclusion criteria

Exclusion criteria are as follows:

(1) A history of mental illness (including personality disorder, schizophrenia, etc); (2) suffering from certain non-communicable diseases that affect the ability to do exercise or that may affect cognition, such as severe aphasia, audio–visual disorders, significant organ failure, a history of coronary artery disease, musculoskeletal disorders or conditions that contraindicate exercise; (3) conditions that impact the composition of the gut microbiome, including inflammatory gastrointestinal disease, irritable bowel syndrome, chronic constipation, chronic diarrhoea, untreated Helicobacter pylori infection and other conditions that affect the gut microbiota; (4) use of certain medications that may affect cognition or affect the gut microbiome; (5) participating in another clinical study.

Recruitment

Participants will be recruited from four residential communities (ie, the clusters) in the Pudong New Area of Shanghai City by online and offline methods such as internet recruitment, poster distribution, leaflet dissemination and the establishment of on-site recruitment stations. To determine eligibility, potential participants will first complete a screening questionnaire and cognitive assessment. Eligible participants will receive information about the study and will have an informed consent discussion with trained research assistants. Interested participants will be scheduled for a baseline assessment. Written informed consent will be obtained by research assistants prior to the baseline assessment.

Randomisation, allocation concealment and blinding

Following the baseline assessment, four residential communities (ie, the cluster), each recruiting 16 eligible participants, will be randomly assigned to the Baduanjin exercise training group or the control group in a 1:1 allocation ratio using a computerised random number generator (www.random.org). An independent research assistant, with no involvement in participant recruitment, assessment or intervention will maintain the allocation sequence. Because this is a behavioural intervention, participants, exercise coaches and intervention supervisors will not be blinded to the treatment allocation. However, outcome assessors and data statisticians will remain blinded to group allocation.

InterventionControl group

Participants in the control groups will be informed to maintain their original lifestyle (not receive any specific exercise training) but will receive three sessions of MCI health education lectures (one session every 8 weeks and 40 min per session) provided by the research assistants on topics such as nutrition, geriatric healthcare and cognitive decline associated with ageing. If participants express interest, researchers will offer free Baduanjin exercise instruction after the trial, along with Baduanjin instruction manuals and video demonstrations.

Baduanjin exercise training group

Based on the same educational programme as the control group, participants in the Baduanjin exercise training group will receive 24 weeks of supervised Baduanjin exercise training with a frequency of 4 days per week and 60 min per day, including 15 min of warm up, 40 min of Baduanjin training and 5 min of cool down. The Baduanjin exercise training will be conducted in two residential community centres with 16 participants per centre. Two experienced coaches from the Shanghai University of Medicine & Health Sciences will be hired to guide the training of the participants. The training regimen of the Baduanjin exercise is derived from the ‘Health Qigong Baduanjin Standard’ established by the State Sports General Administration in 2006.27 It consists of 10 postures, including the preparation and ending posture (details are provided in online supplemental file 1).

To minimise bias from additional physical activity, participants in both groups will be required to record their daily physical activities and dietary intake using a self-designed daily activity and diet diary. Dietary intake and physical activity levels will be monitored using the Food Frequency Questionnaire and the International Physical Activity Questionnaire (Chinese version) to minimise the effect of individual diet and physical activity levels on gut microbiota. Prior to completing the dietary record, participants will receive a food record form, instructions for completing the form and a food scale. A professional will instruct them on how to complete the form. Participants will be required to meticulously record all foods and beverages consumed, including ingredients, weight and cooking methods. Daily nutrient intake will be calculated based on the Chinese Food Composition Table 2009. The Chinese Diet Quality Index will be used as a proxy to assess the diet quality of participants.28

Participant retention and adherence

In order to motivate the participants to actively participate, the research team will use several strategies to increase the adherence to the study: (1) the researchers will explain the benefits of Baduanjin exercise training in detail when they are recruited; (2) the research team will hire the professional coaches to guide their Baduanjin training on the spot; (3) the research assistant will establish a good interaction with participants through the WeChat group; (4) the participants who successfully complete the study programme will be rewarded with 500 RMB incentive money, regardless of which group they belong to.

Outcome assessment

Sociodemographic data of all eligible participants, including gender, age, height, weight, education, marital status, occupation, medical history, lifestyle, medication use, dietary habits and physical activity, will be collected by the recruiters using a self-designed questionnaire. The primary outcomes are change from baseline in global cognitive ability changes and change from baseline in gut microbiota profile and SCFAs. Secondary outcomes are changes from baseline in cognitive subdimensions, such as executive function, visuospatial function, language function and memory function. Cognitive outcomes, including global cognitive ability and the cognitive subdimensions, will be assessed at baseline (week −1~0) and at end of the 24-week intervention (week 25) by the trained postgraduate students in the research team who have completed their undergraduate medical education, have at least 1 year of hospital experience and are familiar with the use of cognitive scales and will be blinded to the allocation results of participants. Faecal samples will be collected on the morning of the cognitive assessment and will be commissioned to a professional laboratory to detect and analyse. A summary of all measurements in this trial is shown in table 1.

Table 1

The schedule of enrolment, interventions and assessments

Primary outcomesGlobal cognitive function

Global cognitive ability will be assessed using the Chinese version of the MoCA scale, which includes cognitive domains such as visuospatial, executive, naming, memory, attention, language and abstraction, and has a total score of 30 points, reflecting overall cognitive function. The MoCA scale is a rapid screening tool for mild cognitive impairment, and an indicator of cognitive function, with higher scores indicating better cognitive performance.29

Gut microbiota and metabolites

Stool samples (approximately 5 g) will be collected from each participant at baseline and after 24 weeks of intervention. The collected stool samples will be frozen and stored at −80°C prior to DNA extraction. Total DNA will be extracted from the stool samples using the DNA Isolation Kit and stored at −20°C before use. Gut microbial diversity and composition will be measured using full-length 16S rRNA gene amplicon sequencing of DNA extracted from the stool sample, while the constraint-based metabolic model for the microbial community of each sample will be conducted. If any of these analyses show an association with the measured cognitive outcomes, further investigation will include metagenomic sequencing and non-targeted metabolomic analysis of faecal samples using ultra-high-performance liquid chromatography–tandem mass spectrometry and gas chromatography-mass spectrometry. Metabolomics analyses will be performed on a subset of samples to improve the resolution of bacterial composition and metabolic functional content.

Secondary outcomesExecutive function

Executive function will be assessed using the Trail Making Test (TMT). The TMT consists of two parts (TMT-A and TMT-B): in part 1 (TMT-A), participants will be asked to connect 25 circled numbers on a paper card in order, while in part 2 (TMT-B), participants will be asked to draw a line alternating between numbers and letters in ascending order. The elapsed times for TMT-A and TMT-B will be recorded separately, and the difference in elapsed time between these two parts will be calculated as follows: TMT elapsed time difference (s)=TMT-B elapsed time (s)—TMT-A elapsed time (s). Longer elapsed times and greater elapsed time differences indicate poorer executive function.30

Visuospatial ability

The Clock Drawing Test will be used to assess visuospatial ability. Participants will be required to draw a closed circle, place 12 Arabic numerals in the correct order and position on the circle, and set the hands to the 11:10 position. One point is awarded for each correct action, with a maximum score of four points. Higher scores indicate better visuospatial functioning.31

Language function

Language function will be assessed using the Chinese version of the Boston Naming Test-30, which includes object naming and word retrieval tasks. This test asks participants to spontaneously name 30 shapes and helps identify naming disorders. A score of 22 or fewer correct names indicates abnormal language function.32

Memory

The Auditory Verbal Learning Test-Chinese version (AVLT) will be used to assess the memory function of participants. The AVLT consists of three subtests: immediate recall, short-term-delayed recall and long-term delayed recognition and is recognised as an objective and sensitive measure for the diagnosis of MCI. In the AVLT test, the 12 two-character Chinese words were categorised into three semantic groups: flowers, occupations and clothing, with four words in each category. The assessor reads the 12 words at random and then the patients are required to recall the words. Test scores are calculated as follows: (1) Immediate recall: the sum of the correct recall words in the first three trials; (2) Short-term delayed recall: the sum of correct responses in free recall after a delay of approximately 5 min; (3) Long-term delayed recall: the sum of correct responses in free recall after a delay of approximately 20 min; (4) Category-cued recall: the sum of the correct responses in the category-cued recall condition and (5) Recognition: the sum of the correct responses in the recognition test.33 The higher the score, the better the function.

Safety measurements

During the intervention period, participants will be continuously monitored for the occurrence of adverse events. Any adverse events will be reported in detail to the research group by the research assistant using an adverse event case report form (CRF). The relationship between the Baduanjin intervention and the severity of adverse events will be evaluated. All serious adverse events will be reported to the ethics committee.

Statistical analysis

Statistical analysis will be conducted by an independent statistician using the SPSS V.25.0 software package on the intention-to-treat principle, with a statistical significance of p<0.05 on both sides. Missing data will be addressed using multiple imputation techniques. The mean (SD) or median (IQR) will be used to describe continuous variables, and the percentages or frequencies will be used to describe categorical variables.

For primary or secondary outcomes on cognitive measures, between-group comparisons at baseline or post-intervention between two groups will be analysed using independent samples t-tests if these variables have a normal distribution, otherwise the Mann-Whitney U test will be used. The mixed linear model with restricted maximum likelihood will be used to determine the interaction effects of intervention by time.

For gut microbial data, the within-sample diversity (α-diversity), including sample richness, taxa abundance, evenness and taxa distribution will be determined using the following indices: Chao 1, Shannon and Simpson’s indices, Abundance-based coverage estimators index and the Good’s Coverage index. Taxa abundance will be expressed as operational taxonomic units and/or amplicon sequence variants. Sequencing reads will be demultiplexed with LotuS (V.1.565) and further processed with the DADA2 pipeline (V.1.6.0) using the RDP classifier V.2.12 for taxonomy assignment (default parameters). Between-sample dissimilarity (β-diversity) will be determined using Bray-Curtis dissimilarity (via a distance-based nonparametric permutational analysis of variance test) and weighted and unweighted UniFrac (via principal coordinate analysis), respectively. Comparisons of relative gut microbiota abundance (α-diversity, β-diversity, etc) between the Baduanjin exercise intervention group and the control group will be performed using linear discriminant analysis effect size. Principal component analysis, partial least squares discriminant analysis and orthogonal partial least squares discriminant analysis will be used to perform the multivariate statistical analysis between groups. In addition, the KEGG34 pathway database and Metabo Analyst V.3.035 will be used to investigate the biochemical pathways associated with the metabolites.

Mediation analysis will be used to determine whether the improvement in cognitive outcomes following the Baduanjin exercise intervention is the result of changes in gut microbiota composition, diversity and metabolites between the two groups, and will be conducted using the bootstrapping method in the Hayes Process Macro for Mediation, Moderation and Conditional Analysis for SPSS (V.25.0; IBM).36

Patient and public involvement

Patients and/or the public were not involved in the design, conduct, reporting or dissemination plans of this research.

Data collection and management

Data will be collected by the outcome assessors using the CRF and then transcribed into the electronic data acquisition (EDC) system, which is a free research manager (ResMan, http://www.medresman.org) provided by the China Clinical Trial Registry that meets the available security standards. The research data will be stored in the EDC in a separate password-protected location.

Ethics and dissemination

Ethical approval for the study was granted by the Ethics Committee of the Shanghai University of Medicine and Health Sciences (2023-GZR-011). A detailed approved Medical Ethics Review Report is available in online supplemental file 2. The study protocol adheres to the ethical guidelines of the Declaration of Helsinki.36 All participants will provide voluntary written informed consent. Potential benefits and risks will be fully discussed prior to participation.

The results of the study will be communicated to the scientific community through local, national or international conferences. We will try to publish the results in high-impact peer-reviewed journals. Key findings from this study will be shared with all participants and disseminated to researchers, health service providers, health professionals and the general public through courses, demonstrations and the internet.

Trial status

At the time of submission, the trial is in the recruitment phase.