An international team led by Dr. David Llewellyn at the University of Exeter Medical School found that study participants who were severely vitamin D deficient were more than twice as likely to develop dementia and Alzheimer’s disease.
Studying elderly Americans who took part in the Cardiovascular Health Study, the team discovered that adults who were moderately deficient in vitamin D had a 53% increased risk of developing dementia of any kind, and the risk increased to 125% in those who were severely deficient.
Similar results were recorded for Alzheimer’s disease, with the moderately deficient group 69% more likely to develop this type of dementia, jumping to a 122% increased risk for those severely deficient.
The study looked at 1,658 adults aged 65 and older who were able to walk unaided and were free from dementia, cardiovascular disease and stroke at the start of the study. The participants were then followed for six years to investigate who went on to develop Alzheimer’s disease and other forms of dementia.
“We expected to find an association between low vitamin D levels and the risk of dementia and Alzheimer’s disease, but the results were surprising,” Dr. Llewellyn said. “We actually found that the association was twice as strong as we anticipated. Clinical trials are now needed to establish whether eating foods such as oily fish or taking vitamin D supplements can delay or even prevent the onset of Alzheimer’s disease and dementia. We need to be cautious at this early stage and our latest results do not demonstrate that low vitamin D levels cause dementia. That said, our findings are very encouraging, and even if a small number of people could benefit, this would have enormous public health implications given the devastating and costly nature of dementia.”
The study also found evidence that there is a threshold level of vitamin D circulating in the bloodstream below which the risk of developing dementia and Alzheimer’s disease increases. The team had previously hypothesized that this might lie in the region of 25-50 nmol/L, and their new findings confirmed that vitamin D levels above 50 nmol/L are most strongly associated with good brain health.