As societies age more and population life expectancy increases, an average of 16–20 % of the later years of life are spent in morbid conditions (Partridge et al., 2018). Cognitive impairment is essentially neurodegenerative, and aging is the greatest risk factor for neurodegeneration (Juan and Adlard, 2019). Most people live much longer now than in the past, but aging impairs sensory, motor, and cognitive functions which reduces quality of life (Niccoli and Partridge, 2012). Loss of cognitive function can lead to dementia, and maintaining cognitive function is a key goal of healthy aging (Mina et al., 2023), making it particularly important to intervene with older people in some way. Cognitive decline in older adults is primarily age-related, making it possible to ameliorate the development of neurodegenerative diseases by altering the mechanisms of aging (Bishop et al., 2010).

In recent years, human behavior movement and related compounds have been more comprehensively studied concerning cognitive function. Grip strength is more consistent with overall strength, and handgrip strength is a simple measure of muscle strength (Cruz-Jentoft et al., 2019) and it can be used as a component to identify health status in older adults (Bohannon, 2019). The underlying structure of grip strength decline is consistent with the idea that it is a common factor in biological aging (MacDonald et al., 2004). Grip strength can be an effective predictor of future risk of disability, morbidity, and mortality, and the relationship between grip strength and mortality has been demonstrated in the elderly population therefore grip strength has been studied as a biomarker of aging (Sayer and Kirkwood, 2015). In addition, a number of studies have pointed out that moderate to high-intensity physical activity exerts a positive effect on cognitive function in humans, and the possible mechanism for this effect is the reciprocal stimulation of neuroplasticity (Erickson et al., 2019; Kraft, 2012).

Current research between grip strength and cognition, a review that included 22 observational studies, suggests that grip strength is correlated with cognitive ability, but it is not clear which variable affects the other at baseline (Kobayashi-Cuya et al., 2018). Results from another systematic review suggest that lower grip strength is associated with cognitive decline and a higher risk of developing dementia (Cui et al., 2021). However, other observational studies have shown that the relationship between low grip strength and cognitive decline does not appear to be significant (Atkinson et al., 2009; Bramell-Risberg et al., 2010). Similarly, some cohort studies have shown a significant bidirectional relationship between grip strength and cognitive impairment (Kim et al., 2019).

In conclusion, some of the existing observational and longitudinal studies still have some limitations, such as differences in region, gender, and measurement tools, the effects of which can make the relationship between grip strength and cognitive impairment less clear-cut and subject to directional and confounding factors in the studies. For the study of causality, MR is considered a complementary approach to randomized controlled trials (RCTs), which can use genetic variants from recent genome-wide association studies as instrumental variables as a means of illustrating causal relationships between exposures and outcomes, with genetic variants being randomly assigned during meiosis, so that MR results are less susceptible to confounding and reverse causality bias (Boehm and Zhou, 2022; Skrivankova et al., 2021). The present study combined a cross-sectional study conducted in 2018–2019 in rural Gongcheng County, Guangxi Province with bidirectional two-sample MR in order to comprehensively assess the directional relationship between grip strength and cognitive function. The results of this study are important for exploring the interaction mechanisms between grip strength and cognition and implementing appropriate interventions to counteract cognitive and physical ability decline.