Folate deficiency may increase the likelihood of developing dementia by 3.5 times, suggests a new study from the UK and Korea.
While a strong association was observed between folate levels, researchers report in the Journal of Neurology Neurosurgery and Psychiatry that levels of vitamin B12 were also weakly associated with the risk of developing dementia.
"In this prospective study of a community population, lower folate concentrations predicted incident dementia and AD over a 2.4 year follow-up period, but no associations were found with baseline vitamin B12 or homocysteine concentrations," wrote the researchers from Chonnam National University Medical School, Institute of Psychiatry (London), and Chonnam National University Hospital.
"Over the follow-up period, dementia occurred more commonly in those with a relative decline in folate and vitamin B12 concentrations or a relative increase in homocysteine concentrations," they added.
Alzheimer's is the most common form of dementia and currently affects over 13 million people worldwide. The direct and indirect cost of Alzheimer care is over $100 bn (€ 81 bn) in the US alone. The direct cost of Alzheimer care in the UK was estimated at £15 bn (€ 22 bn).
By the year 2047, the prevalence of Alzheimer's disease (AD) is expected to quadruple, according to some experts.
The new research followed 518 people (average age 73, 59 per cent women) between 2001 and 2003. All participants were free of dementia at the start of the study, while initial blood tests showed that almost 20 per cent had high levels of homocysteine, while 17 per cent had low vitamin B12 levels and 3.5 per cent were folate deficient
High levels of folate at baseline were associated with higher levels of vitamin B12, and lower levels of homocysteine.
At the end of the study, 45 people had developed dementia, with 34 people being diagnosed with Alzheimer's disease, seven with vascular dementia, and four with "other" types of dementia.
The researchers report that the onset of dementia was significantly more likely in those whose folate levels decreased further over the two years, while homocysteine levels increased.
"In our study, incident dementia was more strongly associated with changes in these factors than baseline concentrations," they wrote. "Although these changes may have an effect on neurodegenerative processes (eg, during stages of mild cognitive impairment), the opposite direction of causation is also possible.
"There is growing evidence that somatic changes associated with dementia are already occurring prior to the onset of the clinical syndrome. These include weight loss and blood pressure decline, and may also include changes in micronutrient concentrations."
They also note that dementia was more likely in those who were older, relatively poorly educated, inactive, and had deposits of the protein ApoE.
The research was supported by a grant from the Korea Health 21 R&D at the Ministry of Health and Welfare.
Commenting independently on the study, Clive Ballard, director of research at British charity the Alzheimer's Society said: "This latest study is one further example of why it is so crucial for people to lead a healthy lifestyle with a balanced diet rich in B vitamins and antioxidants.
"The findings add weight to growing evidence about the important role that dietary factors can play in preventing dementia, including the potential importance of vitamin B12 and folate.
"The potential benefits in preventing or treating dementia can only be fully verified in a rigorous clinical trial, as overlap with other lifestyle factors and lifestyle changes in the very early stages of dementia can give misleading results. There is currently one ongoing clinical trial looking at B12 and folate in this area and we look forward to the results with great interest."
The study also appears to be in-line with results from the Folic Acid and Carotid Intima-media Thickness (FACIT) trial that suggested that folic acid supplementation may slow cognitive performance declines that occur naturally with age.
Source: Journal of Neurology Neurosurgery and Psychiatry
Published online ahead of print, doi 10.1136/jnnp.2007.131482
"Changes in folate, vitamin B12 and homocysteine associated with incident dementia"
Authors: J.-M. Kim, R. Stewart, S.-W. Kim, I.-S. Shin, S.-J. Yang, H.-Y. Shin, J.-S. Yoon