CHAPTER 46: Vitamin B₁₂ and Folate in Dementia

Dementia is a cognitive disorder which affects more than 50% of the world's population over the age of 85 years. It is a multifactorial disorder involving genetic and non-genetic factors. Non-genetic factors include hypercholesterolemia, hypertriglyceridemia, hypertension, diabetes and low vitamin B status. Studies show that cognitive decline associated with old age is further deteriorated by low levels of vitamin B₁₂ and folate along with hyperhomocysteinemia occurring at this age. The age-related decline in B vitamin status has been attributed to poor nutrition due to declining appetite and atrophic gastritis. Low levels of vitamin B₁₂ and folate leads to inhibition of methylation reaction, thereby reducing the availability of methyl groups in the brain. This results in impaired formation of myelin, phospholipids and neurotransmitters. Hyperhomocysteinemia induces neurotoxicity by homocysteine-induced oxidative damage and disturbed glutathione metabolism and N-methyl-d-aspartate receptor activation. At present, B vitamin supplementation shows heterogeneous results in preventing or reversing the cognitive decline. Hence, it remains an open question whether or not these interventions in form of B vitamin supplementation as a combination of folate, vitamin B₁₂ and vitamin B₆ will improve cognitive functions or retard the rate of cognitive decline in older adults with or without dementia.