Correlation of muscle strength with cognitive function and medial temporal lobe atrophy in patients with mild to moderate Alzheimer's disease

Abstract

Objective: To analyze the correlation of muscle strength with cognitive function and medial temporal lobe atrophy (MTA) in patients with mild to moderate Alzheimer's disease (AD). Methods: General information, sarcopenia-related indicators, neuropsychological tests and MTA score were collected in 80 confirmed AD patients (41 mild and 39 moderate patients) and 43 normal controls (NC) from the Memory Disorders Clinic of Department Of Neurology in the Second Affiliated Hospital of Soochow University between January and December 2021. Appendicular skeletal muscle mass index (ASMI), grip strength and 5-times sit-to-stand time and 6-m gait speed were used for assessing muscle mass, muscle strength and physical function, respectively. Cognitive function was assessed by Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment scale (MoCA), Memory and Executive Screening Scale (MES), Digit Symbol Substitution Test (DSST), Digital Span Test (DST) and Verbal Fluency Task (VFT), respectively. DST included Forward Digit Span Test (FDST) and Backward Digit Span Test (BDST). All the subjects underwent 3.0T coronal three-dimensional gradient echo sequence MRI. MTA scale was performed to evaluate the degree of medial temporal lobe atrophy. The differences in the sarcopenia-related indicators, cognitive score and MTA score were analyzed among the three groups, and the partial correlation analysis was performed between the inter-groups. Results: Eighty AD patients (24 males and 56 females) were included, aged (72±7) years old, with 41 mild and 39 moderate patients. Meanwhile, 43 NC included 19 males and 24 females, with a mean age of (70±6) years old. The disease duration in moderate AD patients was longer than that of mild AD patients [34.0 (25.0, 43.5) months vs 24.0 (11.0, 34.0) months, P<0.001]. The differences of sarcopenia-related indicators and MTA score among the three groups were statistically significant (all P<0.001), including 5-times sit-to-stand time [(13.6±1.8) s vs (11.5±1.7) s vs (10.3±1.9) s, P<0.001] and MTA score [2.0 (2.0, 3.0) vs 1.0 (1.0, 2.0) vs 0 (0, 0), P<0.001]. In neuropsychological tests, compared to the NC group, MMSE, MoCA, MES and VFT scores in mild and moderate AD groups were lower (all P<0.001); meanwhile, compared to the mild AD group, the moderate group had lower MMSE, MoCA, MES, DSST and VFT scores (all P<0.001). In sarcopenia-related indicators, muscle strength in particular was correlated with widespread cognitive functioning domains and MTA score in AD patients. Grip strength was positively correlated with MMSE, MoCA , MES, FDST (r=0.387, 0.418, 0.522 and 0.484, respectively, all P<0.001), DSST (r=0.327, P=0.006) and VFT score (r=0.354, P=0.003), and negatively correlated with MTA score (r=-0.631, P<0.001). 5-times sit-to-stand time was negatively correlated with MMSE, MoCA, MES, DSST, FDST, VFT score (r=-0.583, -0.587, -0.814, -0.591, -0.552 and -0.485, respectively, all P<0.001), and BDST (r=-0.355, P=0.003) strongly positively correlated with MTA score (r=0.836, P<0.001). ASMI was positively correlated with MMSE, MoCA, MES, DSST, FDST score (r=0.257, 0.238, 0.428, 0.282 and 0.364, respectively, all P<0.05), and negatively correlated with MTA score (r=-0.377, P=0.001). 6-m gait speed was positively correlated with MMSE, MoCA, MES, DSST, FDST score (r=0.419, 0.486, 0.699, 0.559 and 0.500, respectively, all P<0.001), BDST and VFT score (r=0.384、0.377, respectively, both P=0.001), and strongly negatively correlated with MTA score (r=-0.803, P<0.001). Conclusions: Patients with mild to moderate AD have widespread cognitive impairment. Muscle mass, muscle strength and physical function are all significantly impaired. Compared to muscle mass and physical function, decreased muscle strength is significantly associated with widespread cognitive decline and increased degree of medial temporal lobe atrophy.