Blood Biomarkers and MoCA Scores in MCI and Dementia: The Role of Homocysteine and Hemoglobin in Domain-Specific Cognitive Impairment

Background Serum biomarkers offer a non-invasive approach to support early cognitive assessment, but their association with cognitive function across dementia stages remains unclear. The Montreal Cognitive Assessment (MoCA) is a well-known screening tool, yet its reflection of underlying biochemical changes, particularly in specific cognitive domains, has been less explored. Objective This study investigated the relationship between MoCA scores and plasma levels of homocysteine, hemoglobin, vitamin B12, folate, and vitamin D in individuals with mild cognitive impairment (MCI) or dementia, and whether these biomarkers explained domain-specific cognitive differences. Methods A retrospective cross-sectional study was conducted on 240 individuals aged ≥ 50 years with clinically diagnosed MCI or dementia. MoCA version 7.1 was administered, and biomarker levels were obtained from hospital records. Correlation and group comparison analyses were applied to assess associations between biomarker concentrations, MoCA performance, and dementia subtypes. Results Poorer performance in the executive and visuospatial domains, such as clock drawing and serial subtraction, and lower MoCA scores were linked to elevated homocysteine levels (p < 0.01). MoCA scores showed a positive correlation with higher hemoglobin levels, especially in working memory and attention. Vitamin B12, folate, and vitamin D showed no significant associations with cognitive scores. Comparable trends were found across dementia subtypes. Conclusion Hemoglobin and homocysteine have been identified as important blood-based indicators of cognitive function, namely in the areas of executive, attention, and visuospatial skills, in elderly people with dementia and MCI. While vitamin B12, folate, and vitamin D seem less useful, their combination with MoCA