Several small-sample studies have suggested that sarcopenia and sarcopenic obesity are implicated in cognitive decline. We aimed to prospectively investigate the associations of possible sarcopenia, sarcopenia and sarcopenic obesity with incident dementia, cognitive functions, and brain structure based on the UK Biobank.

A total of 420,916 participants without dementia and cardiovascular diseases at baseline were analyzed. Sarcopenia status was defined according to the European Working Group on Sarcopenia in Older People 2. Obesity was defined according to body mass index. Cox models were applied to evaluate the longitudinal associations.

During a median follow-up of 13.69 years, 4,019 incident all-cause dementia events (including 2,650 Alzheimer’s disease and 527 vascular dementia) were recorded. Comparted with individuals without sarcopenia, the multivariable-adjusted hazard ratios (95% confidence interval) of all-cause dementia were 1.44 (1.32−1.58), 1.37 (1.03−1.82) and 3.06 (1.89−4.93) for those with possible sarcopenia, sarcopenia and severe sarcopenia, respectively. Individuals with sarcopenic obesity (hazard ratios = 1.69, 1.41−2.03) had the highest risk of all-cause dementia than those with obesity only, sarcopenia only or neither. The significant associations remained in all dementia types (Alzheimer’s disease or vascular dementia). In addition, those with sarcopenic obesity was associated with unfavorable cognitive functions, and worse brain structure.

Our findings suggested that possible sarcopenia, sarcopenia and sarcopenic obesity were associated with a higher risk of all-cause dementia and its subtypes.