In our study, the prevalence of MCR was 13.3%. Prior studies have indicated that MCR, as a novel concept for identifying dementia risk, enhances our comprehension of dementia’s pathophysiological mechanisms and enables early dementia prevention[30]. We utilized the LASSO method for features selection, eventually developing and validating the model using five crucial features, and created the nomogram.
The study revealed that weakness and prolonged Five-Times-Sit-To-Stand (FTSS) test duration were independent predictors of MCR. Weakness in this study meant low grip strength. Our finding aligns with prior researches, indicating a correlation between decreased grip strength and a higher prevalence of MCR. For example, Dian Jiang et al.[31] identified a notable linear dose-response association between grip strength and MCR, with the probability of MCR rising by 3% for each 1-kilogram decreasing in hand grip strength (HGS). Studies have shown various potential pathophysiological mechanisms linking reduced grip strength to cognitive decline, such as the generation of pro-inflammatory cytokines[32] and elevated white matter intensity[33]. In addition, higher grip strength may reflect regular physical activity, which has been associated with a reduced risk of dementia in some epidemiological or clinical studies[34]. Regular exercise can help maintain greater muscle strength and enhance cardiovascular function after middle age, contributing to improved health in later years and cognitive function. Similarly, as a validated measure of muscle strength, our study revealed a positive correlation between prolonged FTSS duration and an increased risk of MCR, aligning with the outcomes of Han Xiao’s research[35]. The FTSS test examines participants' ability to transition from sitting to standing positions, a process that is influenced by balance and multiple sensorimotor factors[36], which may explain why FTSS may be associated with cognitive function. The results of our study implied that improving lifestyle and exercise may be ways to prevent MCR syndrome, dementia or other adverse consequences.
Our predictive model showed that chronic pain was also associated with MCR. This correlation has been supported by prior research. Liang Haixu et al.[37] tracked 3711 elderly individuals over a 4-year period and observed that those with chronic pain were about 1.5 times more prone to MCR compared to those without chronic pain (HR 1.5, 95% CI 1.23–1.99). Actually, pain is closely related to cognition, as both can trigger similar brain pathways involving structures like the amygdala, hippocampus, and nucleus accumbens[38]. The link between pain and cognitive decline may be attributed to the atrophy of their overlapping neural networks. Wenhui Zhao et al.[39] found that compared with pain-free individuals, individuals with multisite chronic pain were associated with significantly higher dementia risk, broader and faster cognitive impairment, and greater hippocampal atrophy. In addition, a prominent theory established a connection between pain and cognitive function. The pain interruption model posits that pain impairs cognitive function through distraction, a hypothesis corroborated by clinical research[40]. Our study highlighted the importance of focusing on the elderly population with chronic pain in the future, emphasizing the necessity of making safer and more effective treatment choices for this group.
The study also found that a high limb dysfunction score was an independent predictor of MCR. At present, more and more evidence suggests the significance of limb function in identifying cognitive decline[41–43]. Individuals with cognitive impairment may experience overloading of their brain networks when facing complex tasks involving cognitive responses and functional mobility, which manifests as limb dysfunction[44, 45]. Moreover, people with poor limb function usually have reduced venous return, which may lead to vertebral hypoperfusion, decreasing cognitive function[46, 47]. Therefore, incorporating limb dysfunction score into routine assessments of older adults could help healthcare providers stratify risk to develop interventions for older adults at high risk of MCR.
Moreover, this study found that reduced visual function was associated with a higher risk of MCR. Current studies agree that the underlying mechanism between visual impairment and cognitive decline is unclear. Only a few hypotheses have been proposed for this association. The sensory loss impact theory suggests that vision loss prevents older adults from engaging in activities that are essential to maintaining cognitive function[48]. Another hypothesis is the co-cause hypothesis, which proposes that visual and cognitive decline is due to common factors like inflammation and central nervous system dysfunction[49, 50]. Vision assessment is cost-effective and non-invasive. Timely assessment of vision in older adults and giving appropriate interventions could offer additional benefits. For example, Haotian Lin[51] conducted a controlled clinical trial and found that the improvement of vision after cataract surgery was related to the improvement of cognitive ability and the increase of cortical gray matter volume.
The study is based on a large and nationally representative survey conducted in China, which enhances the generalizability and reliability of our findings. In addition, this study is the first attempt to establish a MCR risk prediction model. Our predictive model can help healthcare professionals screen older adults at high risk of MCR in order to develop early prevention and intervention measures. However, our research also has some limitations. Firstly, The CHARLS database lacks data on certain potential factors like personality traits, sleep medication usage, and pain severity. Secondly, some variables in CHARLS were evaluated through self-report, which may be influenced by recall bias. Additionally, our model was developed and validated based on population data from China, and the research results may not be applicable to other races.