Methods
The protocol for this study was officially registered with INPLASY under the registration number 2023100065. The associated DOI for this registration is 10.37766/inplasy2023.10.0065 .

Two independent investigators (WZ, NX) performed comprehensive literature searches in five pertinent databases: PubMed, Cochrane Library, Embase, Scopus, Physiotherapy Evidence Database and Web of Science. The search time limit was set from the inception of each database to June 1, 2024. The search terms used included: (“Exercise”[Mesh] OR “ exercise ” OR “physical activity ” OR “resistance training” OR “ strength ” OR “ endurance ” OR “ walking ” OR “ yoga ” OR “TaiChi”) AND (“Cognitive Dysfunction”[Mesh] OR “mild cognitive impairment ” OR “MCI”) AND (“systematic review ” OR “meta-analysis”) NOT (“Alzheimer’s disease ” OR “AD”).

We incorporated relevant meta-analyses based on randomized controlled trials (RCTs) to examine the impact of exercise interventions on cognitive function in individuals with MCI. All participants included in the studies were required to have a clinically confirmed MCI diagnosis or met at least one of the following criteria: (1) self-reported memory loss or cognitive decline that disrupts daily functioning, which is not supported by corroborating evidence from family members; (2) age-inappropriate memory deficits, as evidenced by performance on memory and cognitive scales falling below 1.5 standard ( Aarsland et al., 2009 ) deviations from age- and education-matched norms (for example, Wechsler Memory Scale (WMS): 60–79 points; Mini-Mental State Examination (MMSE): 24–27 points; Montreal Cognitive Assessment (MoCA): 14–25 points); (3) intact general cognitive function except for memory, with preserved ability to perform activities of daily living; (4) absence of a dementia diagnosis, and insufficient evidence based on physician reports, patient history, and mental status examinations to diagnose Alzheimer’s disease (AD) or other types of dementia. The included meta-analyses were required to assess interventions involving at least one exercise group, with no restrictions on the specific type of exercise employed, focusing specifically on global cognition as the primary outcome. The control groups were limited to those who did not participate in exercise, engaged only in low-intensity activities such as stretching, or participated in conventional treatment, health education, or a no-intervention control condition. This design allowed for a comprehensive assessment of the effects of various exercise modalities on cognitive function in comparison to non-exercise or minimal-intervention control groups.

Studies were excluded if they met any of the following criteria: (1) non-English language publications; (2) conference proceedings, abstracts, or presentations; (3) duplicate publications; (4) Cochrane meta-analyses in the planning or title registration phase; (5) participant populations consisting of AD patients; (6) intervention groups involving combined exercise and cognitive training, music therapy, or other non-exercise-based modalities; (7) no availability of full-text or extractable data; (8) animal studies; and (9) outcome measures not directly related to cognitive function.

Two investigators (WZ, NX) independently screened and organized the literature and extracted relevant information. The selection process initially involved reviewing the titles and abstracts, followed by cross-checking the extracted data. In cases of disagreement, a third investigator (MF) assisted in the decision-making process. After excluding irrelevant literature through preliminary screening, the full text of the remaining articles was reviewed for final inclusion. The following data were extracted: (1) basic information, such as study title, authors, publication date, journal, number of original studies included, sample size, intervention details, outcome measures, main conclusions, quality assessment tools, meta-analysis registration numbers, and funding sources; (2) methodology for literature evaluation and reporting quality-related content; and (3) qualitative or quantitative results for each outcome measure. Primary outcome measures included the Mini-Mental State Examination (MMSE), Alzheimer’s Disease Rating Scale-Cognitive Subscale (ADAS-cog), and Montreal Cognitive Assessment (MoCA).

Two researchers (WZ, NX) independently assessed the methodological quality of the included studies using the AMSTAR2 scale, which comprises 16 items. Each item was rated as “yes,” “no,” or “partially yes” based on the extent to which evaluation criteria were satisfied. Items 2, 4, 7, 9, 11, 13, and 15 are considered critical. Studies were assigned one of four credibility ratings: “High,” “Moderate,” “Low,” or “Very Low.” A rating of “High” was given if a study had 0 or 1 non-critical flaws, “Moderate” if it had more than one non-critical flaw, “Low” if it had one critical flaw with or without non-critical flaws, and “Very Low” if it had more than one critical flaw. Disagreements during the evaluation process were resolved through discussions with a third(MF) researcher.