Cross-Sectional Associations of Sarcopenia and Its Components with Neuropsychological Performance among Memory Clinic Patients with Mild Cognitive Impairment and Alzheimer's Disease.

Background: The association of sarcopenia with cognitive function in its specific domains remains poorly understood.

Objectives: To investigate the association of sarcopenia and its components with neuropsychological performance among patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD).

Design: Cross-sectional design.

Setting: A memory clinic in Japan.

Participants: The study included 497 MCI/684 AD patients aged 65-89 years.

Measurements: Patients were assessed for muscle mass by bioelectrical impedance analysis, muscle strength by hand grip strength (HGS), and physical performance by timed up and go test (TUG). Sarcopenia was defined as presence of both low muscle strength and low muscle mass. The patients underwent neuropsychological tests, including logical memory, frontal lobe assessment battery, word fluency test, Raven's colored progressive matrices, digit span, and the Alzheimer's disease assessment scale-cognitive subscale (ADAS-cog).

Results: The prevalence of sarcopenia in men and women was 24.1% and 19.5%, respectively. In multiple regression analyses adjusting for confounders, unlike in men, sarcopenia was associated with memory function in women (ADAS-cog, memory domain, coefficient = 1.08, standard error (SE) = 0.36), which was thought likely due to the relationship between HGS and memory function (immediate recall of logical memory, coefficient = 0.07, SE = 0.03; ADAS-cog, memory domain, coefficient = -0.10, SE = 0.03). Of the components of sarcopenia in both sexes, HGS and TUG were associated with visuospatial function and frontal lobe function, respectively.

Conclusions: The specific association of sarcopenia and its components with cognitive domains may provide the key to elucidating the muscle-brain interactions in AD.