1. Introduction
Mild Cognitive Impairment (MCI) is an intermediate stage between normal aging and dementia, often considered a clinical state that precedes Alzheimer's disease (AD) [
1,
2]. The global prevalence of MCI among community-dwelling adults aged 50 and older was over 15% [
3]. In China, the prevalence of MCI among individuals aged 60 and above is 15.5%, with the number of affected reaching 38.77 million [
4]. It is estimated that over 50% of individuals diagnosed with MCI will develop dementia within five years, with only a small percentage will maintain stable cognitive function [
5]. In the absence of timely diagnosis, patients may exhibit impairments in two or more cognitive domains, such as memory, language, executive function, perceptual speed and visuospatial abilities [
6,
7,
8]. These impairments can severely affect the patients’ independence in daily life and place a significant burden on caregivers and families, ultimately increasing societal burden [
9]. Therefore, it is crucial to identify individuals at high risk for MCI as early as possible.
Prior research has identified several risk factors affecting cognitive function in older adults. Demographic characteristics such as age, sex, educational level, and marital status have all been shown to significantly impact cognitive impairment [
10,
11]. A significant body of research has established a link between cognitive decline and various physical health conditions. These include basic activities of daily living (BADL) [
12], instrumental activities of daily living (IADL) [
13], body mass index (BMI) [
14], blood pressure [
15], vision [
16], hearing [
17], and chronic diseases such as diabetes and stroke [
18]. Additionally, lifestyle factors such as exercise [
19], diet [
20], smoking, and alcohol use [
21], have been shown to have a considerable impact on cognitive function in older adults. At the biological level, evidence indicates that sex hormones [
22] and hemoglobin levels [
23] are linked to cognitive dysfunction. Ferri et al. [
24] established a strong correlation between depressive states and cognitive decline. Additionally, Gui et al. [
25] identified a clear association between the APOEε4 allele and MCI. Numerous factors influence cognitive function in the elderly, and risk factors varying across studies. Developing a prediction model for MCI is therefore essential for the early identification, prevention, and treatment [
26].
In prior literature, Huang et al. [
27] developed an MCI prediction model using data from 478 community-dwelling middle-aged and older adults (≥45 years old). The predictors included age, sex, educational level, place of residence, and reading, with an area under the receiver operating characteristic curve (AUROC) of 0.870. This model lacks external validation, and its predictive effect may be biased. Ma et al. [
28] developed an MCI risk prediction model for older adults (≥60 years old) using public datasets. This risk prediction model used different MCI assessment methods during the development and validation phases, which may impact the stability and accuracy of the model. Additionally, MCI prediction models have been developed for other specific patient populations, including those with hypertension [
29], diabetes [
30], and stroke [
31]. While prediction tools for these populations are available, variations in study populations and study designs have resulted in a diversity of model variables. MCI prediction models have also been developed using data from various data sources, including neuro biomarkers like A-β amyloid [
32] and tau protein [
33], neuroimaging variables such as brain microstructure [
34], and genetics such as mitochondria-related genes [
35]. The predictive accuracy of these models has significantly improved; however, implementing these biomarker tests in community settings remains challenging. Consequently, the objective of this study was to develop and validate a risk prediction model, known as CGMCI-Risk, for MCI in community-dwelling older adults. This model aims to help community healthcare professionals identify high-risk MCI groups, thereby facilitating the optimization of prevention and intervention strategies.
4. Discussion
In this study, CGMCI-Risk was developed based on a dataset comprising 6,058 samples, and its external validity was subsequently temporal validated with an additional 4,488 samples. The AUROC values demonstrated consistent performance, with a mean of approximately 0.8, indicating a high degree of discriminative ability. The calibration curve demonstrated excellent consistency, and DCA validated its utility, establishing a robust tool for MCI risk assessment in community-dwelling older adults. The CGMCI-Risk incorporates age, educational level, sex, exercise, garden work, TV watching or radio listening, IADL, hearing, and masticatory function.
Age and sex are significant non-intervention factors in cognitive impairment. The prevalence of MCI increases with age. As a consequence of the aging process, the volume of the cerebral cortex and hippocampus diminishes [
50]. This results in a blockage of information delivery, which in turn impairs cognitive function [
50]. Yesavage et al. [
51] modeling the prevalence and incidence of AD and MCI. Primary found of the model include that the conversion rate from normal cognitive state to MCI increased from 1% per year at age 60 to 11% at age 85. This suggests that age is a significant risk factor for the development of MCI. A meta-analysis of the association between sex and MCI revealed that women are a risk factor for MCI [
52]. The role of estrogen in neurogenesis in the hippocampus is significant, and fluctuations in its levels may be associated with an increased risk of MCI in female [
53]. Furthermore, women are more prone to the formation of ApoEε4-associated neurogenic fiber tangles, which may contribute to an elevated risk of cognitive impairment [
54]. A review of the literature reveals a correlation between educational attainment and a number of factors related to cognitive functioning, including the thickness of the cerebral cortex, gray matter volume, and neural network connectivity [
55]. Individuals with higher levels of education tend to demonstrate superior cognitive functioning [
56], whereas illiteracy or lower educational attainment represents a substantial risk factor for MCI [
57].
There is a strong correlation between IADL and cognitive function. As IADL declines, older adults may also experience a decline in cognitive abilities [
13]. This association may be attributed to the fact that sustained stimulation of cerebral function through IADL preserves the activity and plasticity of the brain's neural networks, thereby assisting in the mitigation of cognitive decline [
58]. A reduction in IADL may also result in a decline in socialization among older adults, which may further impact their cognitive function [
59]. Hearing impairment represents a significant risk factor for the onset of MCI. A study investigating the impact of hearing on cognitive function demonstrated that individuals with normal hearing exhibited superior performance on cognitive assessments [
60]. This may be attributed to the fact that hearing impairment can result in alterations to brain structure and function [
17]. Examples of these changes include a decline in brain signals, degeneration of the auditory cortex, loss of neurons and neuron branches, and a reduction in overall brain volume [
61]. Such alterations may impact the brain's capacity to process and perceive sound, potentially contributing to cognitive decline. Tooth loss can result in difficulty chewing, which may affect nutrient absorption and cognitive function in the brain [
62]. Momose et al. [
63] and Onozuka et al. [
64] have demonstrated increased hemodynamic responses in the prefrontal cortex and hippocampus during chewing, which plays a crucial role in cognitive function. Research has indicated a correlation between tooth loss and chewing difficulties and cognitive decline [
65], while effective mastication has been shown to have a beneficial impact on the prevention of MCI [
66].
Regular exercise has been demonstrated to exert a beneficial influence on the brain [
67]. A research study demonstrated that sustained exercise can delay the onset of cognitive impairment in older adults [
68]. An intervention study by Kim and colleagues also confirmed that exercise may improve cognitive function in older adults aged 65 and above [
19]. Regular exercise has been demonstrated to facilitate the formation of neural connections between regions of the brain that are essential for optimal cognitive function [
69]. Furthermore, it facilitates the release of brain-derived neurotrophic factor (BDNF) in the brain, which is instrumental in promoting neuronal growth, connectivity, and maintenance [
70,
71]. It is hypothesized that gardening may confer benefits with respect to cognitive function in older adults. Findings from a four-year longitudinal study indicate that gardening may be a significant factor in the reversal of MCI in older adults [
72]. In addition to providing enriching stimulation [
73], gardening has been shown to result in significantly higher levels of BDNF, which can lead to improvements in both physical and cognitive functioning [
74]. Furthermore, the role of passive activities such as watching television or listening to the radio in cognitive impairment has been demonstrated. Lin et al. [
75] and Major et al. [
76] have shown that these activities can significantly improve cognitive performance in older adults. However, Jung et al. [
77] posit that television viewing may be associated with an increased risk of cognitive impairment in later life. This may be attributed to the fact that prolonged television viewing is frequently linked to sedentary behavior, which can result in inadequate physical activity or reduced time spent gardening. Consequently, watching television or listening to the radio may become a risk factor [
76].
Currently, more than 55 million individuals worldwide are affected by dementia, with AD representing approximately 60 to 70 percent of dementia cases [
78]. MCI progresses to AD at a rate of 10 to 15 percent per year, whereas the rate of transition to AD in normal older adults is only 1 to 2 percent per year [
79]. Although current clinical interventions may not be capable of curing these diseases, timely recognition and diagnosis are essential for improving patient prognosis and reducing the burden on caregivers [
80]. CGMCI-Risk enhances accessibility and feasibility of assessment and optimizes healthcare worker engagement. It is particularly suited to community settings, providing community healthcare workers with a foundational resource for conducting early cognitive interventions.
The CGMCI-Risk model was developed to identify high-risk groups for MCI in community-dwelling older adults. Although laboratory parameters, imaging features, biomarkers, and genetic indicators have significant potential for MCI prediction, they were excluded in this study due to logistical and operational feasibility in a real-world community setting. In addition, the three-year interval for MCI assessment may introduce bias and fail to capture subtle disease changes. The elevated mortality rate among older adults may also lead to increased data loss and impact assessment precision. The CGMCI-Risk model was developed based on Chinese community-dwelling older adults and while promising for use in community settings, requires further validation for its applicability in different care facilities and cultural backgrounds.
Author Contributions
Conceptualization, J.C., Y.S. and Q.X.; methodology, J.C.; supervision, Y.S. and Q.X.; project administration, Y.S., Q.X. J.C. and K.Y.; investigation, Q.F., K.Y. and L.Z.; data curation, J.C.; resources, K.Y., L.Z. and J.C.; formal analysis, J.P., Q.F. and J.C.; software, Q.F., J.P. and J.C.; validation, Q.F. and J.C.; visualization, J.C. and L.Z.; writing—original draft preparation, J.C.; writing—review and editing, Y.S., Q.X. and J.C.; funding acquisition, Y.S. All authors have read and agreed to the published version of the manuscript.