Results
Eighteen meta-analyses were ultimately included in the analysis after screening 1,762 articles based on specified criteria. Figure 1 illustrates the literature screening process. The list of references deleted after reading the full text can be found in the Appendix S1 .

The included meta-analyses were published between 2018 and 2023, and all the original studies were randomized and controlled. The largest study included 2,526 participants and the smallest had 182 participants, involving a total of 18,461 individuals. The interventions in the trial groups consisted of aerobic, physical, mental, resistance, and multipart exercises. The control group in the randomized trials maintained their regular daily activities without any specific exercise interventions. Regarding methodological quality assessment tools, 12 studies utilized the Cochrane Collaboration Network RoB risk assessment tool, four employed the PEDro scale, one used the Cochrane Collaboration Network RoB and PEDro, and one applied the EPHPP for risk assessment. All 18 studies consistently indicated that exercise effectively improves cognition in older adults with MCI. The basic characteristics of the included studies are presented in Table 1 .

Notes:

RCT (randomized controlled trial), NRCT (non-randomized controlled trial); ① for ADAS-cog, ② for MMSE, ③ for MOCA, ④ for COR-SOG,⑤ for NCSE.

The methodological quality of the 18 included meta-analyses was assessed using the AMSTAR2 scale. The results showed that, in terms of quality, one study was rated as ‘moderate’, seven were rated as ‘low’, and ten were rated as ‘very low’. The detailed results are presented in Table 2 .

Notes:

Y Yes PY Partially yes N No 1 Whether the research questions and inclusion criteria are detailed 2 Provide preliminary design scheme (registration number) 3 Explain the reasons for the inclusion of the study type 4 Use a comprehensive search strategy 5 Two-person repeated literature screening was used 6 Two-person repetitive data extraction was adopted 7 Provide a list of exclusions and reasons 8 Describe in detail the basic features included in the study 9 Use appropriate tools to assess bias risk 10 Report on funding sources included in the study 12 Assess the impact of the risk of bias on the outcome 13 Consider the risk of bias included in the study 14 Heterogeneity of the findings was assessed 15 Evaluate the possibility of publication bias 16 Report relevant conflicts of interest

Yes

Partially yes

No

Whether the research questions and inclusion criteria are detailed

Provide preliminary design scheme (registration number)

Explain the reasons for the inclusion of the study type

Use a comprehensive search strategy

Two-person repeated literature screening was used

Two-person repetitive data extraction was adopted

Provide a list of exclusions and reasons

Describe in detail the basic features included in the study

Use appropriate tools to assess bias risk

Report on funding sources included in the study

Assess the impact of the risk of bias on the outcome

Consider the risk of bias included in the study

Heterogeneity of the findings was assessed

Evaluate the possibility of publication bias

Report relevant conflicts of interest

The MMSE is a concise tool for assessing cognitive impairment, offering ease of administration, short duration, and objective results. It is widely used in the clinical, research, and community settings. However, it has limitations such as susceptibility to factors including education level, age, and cultural background, and low sensitivity to mild or subclinical cognitive impairment. Fifteen studies ( Biazus-Sehn et al., 2020 ; Ahn & Kim, 2023 ; Law et al., 2020 ; Song et al., 2022 ; Gómez-Soria et al., 2022 ; Han et al., 2023 ; Lin, Chen & Cheng, 2023 ; Yuan, Li & Liu, 2022 ; Zhang et al., 2019 ; Zhou et al., 2020 ; Zhou & Li, 2022 ; Zhu et al., 2020 ; Zou et al., 2019 ; Pisani et al., 2021 ; Cai et al., 2023 ) examined the effects of exercise interventions on MMSE scores in patients with mild cognitive impairment, 13 of which showed that exercise was effective in improving MMSE scores, with only two not significantly different from controls.

The ADAS-cog evaluates cognitive function in patients with MCI and MD and is second only to the MMSE in clinical trials. Seven studies ( Biazus-Sehn et al., 2020 ; Ahn & Kim, 2023 ; Zhou et al., 2020 ; Zhu et al., 2020 ; Pisani et al., 2021 ; Song et al., 2018 ; Zhang et al., 2020 ) examined the effects of exercise interventions on ADAS-Cog scores in patients with mild cognitive impairment. All seven studies demonstrated that exercise effectively reduced ADAS-Cog scores.

The MoCA scale is a rapid screening tool for mild cognitive impairment (MCI) that assesses eight cognitive domains: attention and concentration, executive function, memory, language, visual-constructive skills, abstract thinking, calculation, and orientation. Eleven studies ( Biazus-Sehn et al., 2020 ; Song et al., 2022 ; Han et al., 2023 ; Lin, Chen & Cheng, 2023 ; Yuan, Li & Liu, 2022 ; Zhou et al., 2020 ; Zou et al., 2019 ; Cai et al., 2023 ; Song et al., 2018 ; Zhang et al., 2020 ; Yu et al., 2021 ) investigated the effect of exercise interventions on MoCA scores in patients with MCI. Ten of these studies showed that exercise effectively improved MoCA scores, while one study found no significant effect.

The NCSE is a standardized cognitive assessment scale that allows the initial screening and evaluation of patients based on their cognitive status. The NCSE covers the domains of orientation, concentration, language (comprehension, repetition, and naming), structural organization, memory, numeracy, and reasoning (similarity and judgment) and can more sensitively reflect problems in cognitive function and the degree of cognitive impairment. Law et al. (2020) , in examining the effects of an exercise intervention on NCSE scores in patients with mild cognitive impairment, showed that exercise was effective in improving NCSE scores.

The COR-SOG scale was used to measure cognitive reserves. Cognitive reserve refers to an individual’s ability to cope with cognitive decline and neurological impairment, which allows them to maintain better cognitive function in the face of cognitive impairment. Law et al. (2020) , in examining the effects of an exercise intervention on COR-SOG scores in patients with mild cognitive impairment, showed that exercise was effective in improving COR-SOG scores.