Low Vitamin D and Its Association with Cognitive Impairment and Dementia

Abstract

Vitamin D is a neurosteroid hormone that regulates neurotransmitters and neurotrophins. It has anti-inflammatory, antioxidant, and neuroprotective properties. It increases neurotrophic factors such as nerve growth factor which further promotes brain health. Moreover, it is also helpful in the prevention of amyloid accumulation and promotes amyloid clearance. Emerging evidence suggests its role in the reduction of Alzheimer’s disease hallmarks such as amyloid-beta and phosphorylated tau. Many preclinical studies have supported the hypothesis that vitamin D leads to attentional, behavioral problems and cognitive impairment. Cross-sectional studies have consistently found that vitamin D levels are significantly low in individuals with Alzheimer’s disease and cognitive impairment compared to healthy adults. Longitudinal studies and meta-analysis have also exhibited an association of low vitamin D with cognitive impairment and Alzheimer’s disease. Despite such evidence, the causal association cannot be sufficiently answered. In contrast to observational studies, findings from interventional studies have produced mixed results on the role of vitamin D supplementation in the prevention and treatment of cognitive impairment and dementia. The biggest issue of the existing RCTs is their small sample size, lack of consensus over the dose, and age of initiation of vitamin D supplements to prevent cognitive impairment. Therefore, there is a need for large double-blind randomized control trials to assess the benefits of vitamin D supplementation in the prevention and treatment of cognitive impairment.

Association of vitamin D metabolites with cognitive function and brain atrophy in elderly individuals - the Austrian stroke prevention study

“…A study of Johansson et al supports this view as it showed an indirect association between lower 25(OH)D and acetylcholinesterase activity in cerebrospinal fluid [ 13 ]. Another mechanism that might play a role is the vitamin D-related upregulation of neurotrophic factors, such as NGF, GDNF, and NTF3 [ 11 ], which are also known to exert enhancing effects on cognition [ 5 , 59 , 60 ].…”

Can Brain Health Be Supported by Vitamin D-Based Supplements? A Critical Review

“…The vitamin-D-supplemented group (supplement contained 4.0 μg (160 IU) of vitamin D and other trace elements) had a better cognitive performance ( p < 0.01) in the different cognitive tests (seven cognitive tests, including the MMSE) compared to the placebo group [ 174 ]. Another prospective pre–post interventional study, which included 80-year-old subjects from a memory clinic, found that those who received oral vitamin D3 supplementation (800 IU per day or 100,000 IU per month) experienced improved global cognition and executive functioning abilities over a 16-month follow-up period compared to controls [ 175 ]. Bailon et al [ 176 ], in its systematic review of meta-analysis cognition data (using the MMSE) provided suggestive evidence of a possible relationship between vitD and cognitive decline, but the nature of this relationship remained unclear.…”

The Role of Inflammatory Diet and Vitamin D on the Link between Periodontitis and Cognitive Function: A Mediation Analysis in Older Adults

“…In fact, adherence to proinflammatory dietary patterns was associated with greater cognitive decline [ 23 , 24 ], while dietary anti-inflammatory patterns reduce the inflammatory burden in periodontitis lesions [ 25 ]. Additionally, vitamin D deficiency has been growing attention reasonably in dementia [ 26 , 27 , 28 ] and periodontitis [ 29 ] since lower vitamin D intake associates with a higher risk of both conditions. However, the mediating role of inflammatory diet and vitamin D on the association of periodontal status and cognitive function has never been investigated.…”