Differences in lean mass and sarcopenia between individuals with Alzheimer's disease and those without dementia: A systematic review and meta-analysis of observational studies

Background: Studies have observed that individuals with Alzheimer's disease (AD) tend to have lower lean mass and higher rates of sarcopenia.

Objective: This review aims to assess differences in lean mass, sarcopenia, and its components between individuals with AD and those without dementia (WD).

Methods: Searches were conducted in the Medline, Web of Science, Embase, Scopus and Latin American and Caribbean Health Scientific Literature. Observational studies comparing lean mass, sarcopenia, and its components in the populations of interest were included. We used the Joanna Briggs Institute (JBI) scale to assess methodological quality. Mean differences (MD) and standardized mean differences were calculated for the meta-analyses.

Results: Four studies with 2035 individuals found that those with AD had significantly lower upper and lower limb lean mass, and skeletal muscle mass index compared to WD individuals. AD individuals also had a higher sarcopenia prevalence (41.33% versus 20.66%) and significant reductions in handgrip strength, lower limb muscle strength, and gait speed compared to WD individuals. The JBI scale analysis showed high agreement among the studies (k = 1.00, p = 0.046).

Conclusions: Individuals with AD have lower lean mass, higher rates of sarcopenia, and reduced muscle function compared to those without dementia. While the results suggest the need for early screening programs and integrated therapeutic interventions to improve clinical outcomes and quality of life for individuals with AD, it is important to consider that biases inherent in observational studies may compromise the quality of the evidence. Therefore, further research, preferably clinical trials, is needed to confirm these associations.