•Dementia patients had significantly higher concentrations of homocysteine, methylmalonic acid and lower folate and plasma 5-methyltetrahydrofolate•No difference in DNA methylation between patients and controls•A trend of higher DNA methylation in VaD patients observed •Global DNA methylation was associated with markers of folate status, creatinine, glucose and PON1 and ILB1 polymorphisms. The gene discussed is PON1; the disease is dementia.