By Rob Winwood
Advancing age is often accompanied by cognitive decline. The extent of cognitive decline varies from mild forgetfulness to mild cognitive impairment (MCI) to full blown dementia. It has been shown that approximately half of people diagnosed with MCI will go on to develop dementia within five years (2).
Lifestyle and nutrition are modifiable risk factors for the onset of cognitive decline in the elderly. In particular, high homocysteine and low folic acid levels in blood plasma have been regularly associated with cognitive decline (3). Randomised controlled trials with interventions using B vitamins have been equivocal, with a 2010 meta-analysis showing no beneficial effect (4).
More recently, the Homocysteine and B-Vitamin in Cognitive Impairment (VITACOG) study demonstrated the protective effect of B vitamins against cognitive impairment. Indeed, supplementation of B vitamins for two years in the study resulted in a reduction of brain shrinkage of approximately 30 percent (5). There is some evidence that residents of care homes are deficient in vitamin B12 (6).
Jerneren et al. (7) reworked data from a human double-blinded, randomised controlled trial that had shown that homocysteine-lowering B vitamins were able to reduce brain shrinkage in people with MCI. They found the beneficial effect was highly dependent on the patient’s plasma docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) status. In the highest DHA/EPA tertile, the average brain atrophy rates were reduced by an average of 40 percent, whereas there was no reduction at all in the lowest tertile.
To date, little work has been carried out on the relation between vitamin B6 plasma levels and cognitive decline. A new study (1) carried out in a population of 155 healthy older people in Northern Ireland with an average age of 69 years were monitored for cognitive decline using the Mini-Mental State Examination (MMSA) over a four year period. Low vitamin B6 (pyridoxine) status was shown to increase the risk of accelerated cognitive decline 3.5 to 4 fold. Vitamin B6 is intimately involved in the synthesis of neurotransmitters including dopamine and serotonin (8). None of the other B vitamins gave a significantly protective effect.