[Vitamin D and cognition in the elderly].

The understanding of the role of vitamin D in maintaining good health has considerably increased in the recent years. There is a growing evidence that vitamin D has not only a beneficial effect to prevent osteoporosis and the risk of falls in the elderly, but also may reduce incidence of cancers, infections, autoimmune, cardiovascular and neurologic diseases, and psychiatric disorders. Laboratory studies yield a biological plausibility for a positive contribution of vitamin D to brain functions: vitamin D receptor and 1,α-hydroxylase, the terminal calcitriol-activating enzyme, are widely distributed in both the fetal and adult brain. Vitamin D may be involved in neuroprotection, control of proinflammatory cytokine induced cognitive dysfunction and synthesis of calcium-binding proteins and neurotransmitter acetylcholine. However, the observational studies conducted in humans are still inconclusive, given the various tests of the cognitive functions that have been used, the performance of the studies either in patients or in healthy subjects, and different designs and/or confounding factors. The role of the vitamin D receptor in the pathophysiology of cognitive decline, incidence of Alzheimer's disease or vascular dementia and/or cognitive decline with respect to previous plasma 25OHD concentration, and the effect on cognition of vitamin D supplementation should be explored in further studies.