Homocysteine and B vitamins in mild cognitive impairment and dementia.

Elderly subjects with mild cognitive impairment have a high risk for conversion to Alzheimer's disease or are already in a preclinical dementia stage. By cross-sectionally comparing subjects in prodromal and early phases of dementia with non-demented controls, we tested the hypothesis whether low serum vitamin B12 and folate and high plasma total homocysteine concentrations precede or are a consequence of dementia onset. From a large population of 623 consecutive subjects seen at the Memory Clinic (Ospedale Beata Vergine, Mendrisio, Switzerland), 433 subjects could be included in the analyses: 79 elderly controls, 218 Clinical Dementia Rating 0.5 subjects, and 136 demented patients (111 with Alzheimer's disease and 25 with vascular dementia). As in an earlier report on a smaller sample of the same population (n=228), the lowest folate tertile was strongly associated with mild cognitive impairment (adjusted OR=3.1) and Alzheimer's disease (adjusted OR=4.0). Hyperhomocysteinemia showed a significant association not only with Alzheimer's disease (adjusted OR=3.1) but, at variance with the previous report, also with mild cognitive impairment (adjusted OR=2.6). Present reanalysis results suggest that subclinical folate deficiency and hyperhomocysteinemia might predate dementia onset, findings to be confirmed by longitudinal studies.