Folate deficiency is associated with a tripling in the risk of developing dementia among elderly people, suggests research published ahead of print in the Journal of Neurology Neurosurgery and Psychiatry.
The researchers tracked the development of dementia in 518 people over two years from 2001 to 2003. All participants were over the age of 65 and lived in one rural and one urban area in the south of the country.
Validated tests were carried out at the start and end of the two year period to find out if they had a dementing illness.
Similarly, blood tests were taken to assess levels of folate, vitamin B12, and the protein homocysteine, and how these changed over time.
High levels of homocysteine have been associated with cardiovascular disease.
At the start of the two year period, almost one in five people had high levels of homocysteine, while 17% had low vitamin B12 levels and 3.5% were folate deficient.
The higher the levels of folate to begin with, the higher were vitamin B12 levels, and the lower those of homocysteine.
By the end of the study, 45 people had developed dementia. Of these, 34 had Alzheimer's disease, seven had vascular dementia, and four had "other" types of dementia.
Dementia was more likely in those who were older, relatively poorly educated, inactive, and had deposits of the protein ApoE.
The onset of dementia was significantly more likely in those whose folate levels then fell further over the two years, while their homocysteine levels rose.
People who were folate deficient to begin with, were almost 3.5 times more likely to develop dementia.
The authors suggest that changes in micronutrients could be linked with the other typical signs that precede dementia, including weight loss and low blood pressure.
While weight loss is unlikely to alter micronutrients levels in the blood, it may indicate dietary changes in the quality of quantity of food intake.