Homocysteine and cognitive impairment in Parkinson's disease

Introduction. The relationship between homocysteine (Hc) and vascular diseases has been known for more than 30 years. Lately, Hc has also been related to cognitive and motor impairment. In Parkinson's disease (PD), chronic treatment with levodopa could induce higher levels of Hc, and thus may increase risk of cognitive impairment. Aims. To confirm that PD patients treated with levodopa have higher levels of Hc and to establish a relationship between Hc, folic acid and vitamin B-12 levels. Also, we studied a possible link between those variables and cognitive function. Patients and methods. 58 patients with diagnosis of PD were included (45 under treatment with levodopa). Basal levels of Hc, vitamin B-12 and folic acid were determined. Forty five patients underwent neuropsychological evaluation. Results. Hc levels were significantly higher in patients taking levodopa and were not related to levodopa dosage or treatment duration. There was a negative correlation between Hc levels and those of vitamin B-12 and folic acid in men but we found no such correlation in women. Entacapone was not found to reduce Hc levels. Hc levels were significantly higher in patients with cognitive impairment (9 out of 45 patients). Conclusions. Our study confirms presence of high levels of Hc in PD patients under treatment with levodopa, more evident in patients with cognitive impairment.