The effect of serum homocysteine, vitamin B12, and folate levels on cognition in Parkinson\'s disease and Parkinson\'s disease dementia

Homocysteine is an amino acid formed during methionine metabolism that contributes to neurodegeneration by inducing an excitotoxic response. This study aimed to investigate the relationship between cognitive impairment and serum homocysteine, vitamin B12 and folate levels in Parkinson\'s disease (PD). A total of 64 patients, 46 with PD and 18 with Parkinson\'s Disease Dementia (PDD), who were followed up in the Movement Disorders Outpatient Clinic, were included in the study. To assess cognitive performance, both patient groups underwent the Standardized Mini-Mental State Examination (MMSE) and a clock drawing test. The correlations between serum vitamin B12, homocysteine and folate levels, and cognitive test scores were evaluated for both patient groups. In the PD group, higher levels of vitamin B12 and folate, as well as lower homocysteine levels, were found compared to the dementia group, with statistical significance observed only for vitamin B12 levels. In terms of the MMSE total scores, as well as its subcategories; in the registration, recall, and attention sections, PD patients were found to perform better than the dementia group. A negative correlation of 32.2% was found between MMSE total scores and homocysteine levels, while a positive correlation of 54.2% was observed between folate levels and attention. A positive correlation was found between the total MMSE scores and clock drawing test scores in both patient groups, but no significant relationship was found between clock drawing test scores and serum vitamin levels, or homocysteine levels. In PD, a negative correlation was observed between homocysteine levels and total MMSE scores, while a positive correlation was found between folate levels and attention in PDD.