VITAMIN D UPDATE: New Study Supports Links Between Dementia And Vitamin D Deficiency. “The researchers discovered that participants with a moderate vitamin D deficiency had a 53% increased risk of developing any form of dementia, and those with a severe deficiency had a 125% increased risk. Similar results were also found for the risk of developing Alzheimer’s, which is the most common form of dementia. Interestingly, they found that there was a threshold level of 50nmol/L vitamin D in the serum, below which the risk of dementia and Alzheimer’s was markedly increased.”