Mild cognitive impairment (MCI) was a common condition, particularly among older adults, characterized by a decline in cognitive function that exceeded age-related expectations. Memory impairment was a primary symptom of MCI, but it did not significantly interfere with daily activities.1 The prevalence of MCI was reported as 6.7% in individuals aged 60 to 64 years, 8.4% in those aged 65 to 69 years, 10.1% in in those aged 70 to 74 years, 14.8% in those aged 75 to 79 years, and 25.2% in those aged 80 to 84 years.2 MCI was a typical intermediate state between the normal aging process and dementia,3 and there was sufficient evidence to believe that MCI can increase the risk of progression to dementia.4 In one study, the annual progression rate of MCI to dementia has been reported to be 10–20%.5 Patients with dementia can experience delusion, depression, apathy, irritability, sleep disorder, and even the loss of self-care ability, which caused a worsening quality of life.6,7 However, it was important to note that a diagnosis of MCI did not necessarily mean that dementia will develop, and almost half of the patients can regain normal cognitive function.8 Several studies have indicated that interventions tailored to individual lifestyles may help delay or prevent the onset of dementia.9 Given that there is currently no specific and effective medicine for treating MCI, developing non-pharmaceutical interventions to slow cognitive decline has become increasingly vital.10,11

Exercise, which was a type of planned, organized, and repeated physical activity aimed at improving or maintaining physical health, was essential for healthy aging. It can help delay, prevent, or manage chronic diseases commonly faced by older adults, and also reduce the risk of premature death.12 Previous studies have found that exercise can enhance the functional connectivity of white matter tracts to improve signal transduction and increase the generation of new neurons in the hippocampus to enhance cognitive functions controlled by the hippocampus.13 With the advantages of low cost and easy access, exercise was particularly attractive in the public health environment. The 2018 guidelines updated by the American Academy of Neurology (AAN) first recommended that individuals with MCI should engage in regular exercise.2 Recent meta-analyses also revealed that exercise could significantly improve memory and reduce behavioral problems.14,15 It was noteworthy that there have been limited previous meta-analyses investigating the effects of different types of exercise on global cognitive function. And it was essential to study this topic to improve our comprehension of the connection between exercise and cognitive function, and to develop appropriate exercise programs. Moreover, depression symptoms,16 poor sleep quality,17 and impaired balance18 were frequently observed in adults with MCI. Evidence suggested that improving these conditions may benefit individuals’ quality of life and delay cognitive decline.19,20 However, the effects of exercise on depressive symptoms, balance, and sleep quality in people with MCI remained unclear and needed to be confirmed by quantitative meta-analysis. Hence, the purpose of this study was to further examine the effects of exercise on global cognitive function, balance, depression symptoms, and sleep quality, intending better to understand the multifaceted benefits of exercise for patients.