• Sarcopenia-related traits (fat-free mass, grip strength, walking speed) are positively causally associated with cognitive function in European populations.
• Walking speed shows the strongest positive causal effect on cognitive function (OR=3.069), suggesting it may be a key indicator.
• Reverse analysis indicates cognitive function only causally affects walking speed, not muscle mass or grip strength.
• The study supports the 'muscle-brain axis' hypothesis and suggests sarcopenia could be a predictor for cognitive impairment.