Hyperhomocysteinemia is associated with cognitive impairment in multiple sclerosis

Hyperhomocysteinemia (HHcy) has been associated with cognitive impairment in various neurological diseases. Cognitive impairment occurs early in multiple sclerosis (MS). Conflicting data have been reported regarding plasma total homocysteine (tHcy) levels in MS patients, and the impact of HHcy on cognitive impairment in MS is not known. This study investigated whether plasma total homocysteine levels are increased in MS and if HHcy is associated with cognitive impairment in MS. We compared tHcy levels in 94 patients with MS and 53 healthy age-matched controls. We used a neuropsychological test battery that included the Raven's Coloured Progressive Matrices, the Visual Search Test, the Trail Making Test A and B, the Immediate and Delayed Recall of a Short Story, the 30 Paired Word Associates, the Rey-Osterrieth Complex Figure Test, and the Semantic and Verbal Fluency Tests. Clinical (sex, age, type of MS, relapse, disease duration, coexisting disease, smoking habit, and physical disability) and laboratory variables (HHcy, low serum levels of folate and vit.B12, MTHFR genotype) were evaluated for their ability to predict cognitive impairment. The mean tHcy was higher in patients (13.19 micromol/L, SD5.58) than in controls (9.81 micromol/L, SD2.53; p < 0.001). Univariate analysis determined the following factors to be associated with cognitive impairment: higher age at observation, chronic progressive course of disease, longer disease duration,moderate or severe physical disability, and frequency of HHcy. With multivariate regression analysis, there remained a significant association only between frequency of HHcy and cognitive impairment (beta 0.262, p = 0.01). We conclude that tHcy levels are increased in MS and that HHcy is associated with cognitive impairment in this disease.