Exploring Vitamin D as a Modifiable Risk Factor in Cognitive Decline and Dementia

Background/Objectives: Dementia is a progressive, multifactorial neurodegenerative syndrome that poses a major public health challenge, with an increasing number of cases due to an aging population. Vitamin D (vitD) is crucial not only for bone and calcium homeostasis, but also as a neuroactive steroid that influences brain functions such as neurotransmission, neuroprotection and immunomodulation. Emerging evidence suggests that vitD deficiency may be a modifiable risk factor for the development of dementia. Thus, the aim of this review is to understand the possible role of vitD as a modifiable risk factor in the prevention of dementia. Methods: Research was conducted in the PubMed and Scopus databases using combinations of the MeSH terms ‘calcitriol’, ‘dementia’, ‘vitamin D receptors’, and ‘brain function’ for articles from 2014 until 2026. Results: The analysis of the 30 articles retrieved exhibited a significant association between vitD deficiency and an increased risk of dementia. Longitudinal studies and meta-analyses have indicated an increased risk of dementia and Alzheimer’s disease proportional to the severity of the deficit. A significant association with vascular dementia was also highlighted, with the risk increasing synergistically in the presence of hypertension. Conclusions: The evidence reviewed suggests that both vitD deficiency and insufficiency are strongly associated with increased risk of dementia, particularly Alzheimer’s disease and vascular dementia. Addressing vitD deficiency by maintaining adequate levels is proposed as a potentially effective preventive strategy against cognitive decline and dementia.