Link between Alzheimer’s and vitamin D deficiency

Low levels of vitamin D are associated with all-cause dementia, including Alzheimer’s disease (AD), according to the largest multicenter population study published Aug. 6 in Neurology. 

The brain is scattered with 1,25-dihydroxyvitamin D3 receptors and the enzyme that synthesizes bioactive vitamin D. Previous research has alluded to the possibility of low serum vitamin D concentrations being connected to prevalence of dementia and AD. In vitro research has shown vitamin D motivating macrophages to clear out amyloid plaques and reducing amyloid-related neurotoxicity and cell death.

Thomas J. Littlejohns, MSc, from the University of Exeter Medical School in Exeter, United Kingdom, and colleagues sought to evaluate the role of vitamin D concentration in the risk of developing dementia. Even though two previous studies, both smaller scale, showed conflicting results, the results of this study revealed very clear and significant correlation between low serum 25-hydroxyvitamin D (25(OH)D) concentrations and the development of dementia.

“We have conducted what is to our knowledge the first large, prospective, population based study to examine vitamin D concentrations in relation to a comprehensive adjudicated assessment of dementia and AD,” wrote Littlejohns et al. “We observed a strong monotonic association between 25(OH)D concentrations and the risk of both incident all-cause dementia and AD. This association was robust to adjustment for a range of potential confounders and the exclusion of dementia cases that occurred within a year of baseline.”

For this study, researchers used liquid chromatography-tandem mass spectrometry to test the serum (25(OH)D) concentrations of 1,658 elderly participants with no sign of dementia, stroke or cardiovascular disease as a part of the U.S. Cardiovascular Health Study between 1992–1993 and 1999. After a mean follow-up of a little more than five years, a total of 171 participants had been diagnosed with all-cause dementia and, of these, 102 patients had AD.

A multivariate analysis showed a significantly stronger risk of developing dementia and AD for those who had lower levels of vitamin D.

Further research will have to be conducted to look into the possibility of reverse causation. The investigators noted that low vitamin D could be caused by the dietary changes and less time outside associated with dementia and not the other way around.