Study: Vitamin D and brain health: an observational and Mendelian randomization study. Image Credit: Lightspring / Shutterstock

Study links low vitamin D levels to dementia risk

The American Journal of Clinical Nutrition recently published a study that describes the impact of vitamin D status on brain health. Study results show that vitamin D deficiency increases the risk of dementia.

Study: Vitamin D and brain health: an observational and Mendelian randomization study. ​​​​​​​Image credit: Lightspring / Shutterstock

Background

Vitamin D, a precursor hormone, is known to influence brain health by modulating neurotrophic growth factors, inflammation, and thrombosis. Vitamin D status in the body is typically monitored by measuring blood levels of 25-hydroxyvitamin D, a form of vitamin D produced in the liver. The prevalence of vitamin D deficiency (<25 nmol/L) is estimated to be 5% - 50% depending on geographic location and demographic factors.

According to the available literature, neurodegenerative diseases and cognitive decline are associated with changes in brain size and shape (brain morphometry). An association between vitamin D status and brain morphometry has also been found in the literature. In this context, a large systematic review concluded that vitamin D deficiency is associated with lower brain volume.

This study investigated the association between vitamin D status and various brain neuroimaging functions. They also investigated whether severe vitamin D deficiency could increase the risk of dementia and stroke.

Study design

Researchers collected prospective data from the UK Biobank to examine the effect of 25-hydroxyvitamin D concentrations on neuroimaging outcomes and the risk of dementia and stroke.

They investigated underlying causal factors for neuroimaging outcomes and dementia and stroke using non-linear Mendelian randomization analysis. In Mendelian randomization, measured variation in known genes is used to examine the causal effect of modifiable risk factors on health outcomes in observational data.

Important observations

Analysis after adjustment for socioeconomic factors revealed a strong association between 25-hydroxyvitamin D concentrations and neuroimaging functions.

A non-linear association was observed between 25-hydroxyvitamin D concentrations and total brain volume, white and gray matter volume, and hippocampal volume. Both low and high concentrations of 25-hydroxyvitamin D were found to be associated with lower total brain, white matter, and gray matter volumes. This association was stronger in men than in women.

Furthermore, an association was observed between lower concentrations of 25-hydroxyvitamin D and the volume of white matter hyperintensity. White matter hyperintensities are indicators of structural brain changes associated with a number of serious diseases, including cognitive decline and stroke.

The effect of 25-hydroxyvitamin D concentrations on the risk of dementia and stroke was monitored in the study. Participants with the lowest concentration of 25-hydroxyvitamin D showed the highest risk of dementia and stroke.

Mendelian randomization

A non-linear inverse correlation was observed between genetically determined vitamin D status and risk of dementia. Participants with lower concentrations of 25-hydroxyvitamin D showed the highest risk of dementia. Specifically, participants with 25 nmol/L hydroxyvitamin D showed a 54% higher risk of dementia compared to those with 50 nmol/L 25-hydroxyvitamin D.

No association of 25-hydroxyvitamin D concentration with neuroimaging features and stroke risk was observed in a Mendelian randomization analysis. Further analysis revealed that 17% of dementia could be prevented by increasing the concentration of 25-hydroxyvitamin D to 50 nmol/L.

Study significance

The results of the study show that vitamin D deficiency can significantly affect brain health. Specifically, the study shows that individuals with low levels of vitamin D are at a higher risk of developing dementia.

The findings provide a crucial opportunity to prevent dementia, the researchers said. They also emphasized the need for larger Mendelian randomized trials to confirm the proposed causal relationship between 25-hydroxyvitamin D concentrations and brain morphometry.[if–>

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