Adding to an ever-growing body of evidence, a new study has found that vitamin D deficiency is associated with a substantially increased risk of developing Alzheimer’s and dementia. While previous studies have drawn similar conclusions, this is the largest, most robust study carried out to date. The results have been published in the journal Neurology.
Vitamin D is an essential vitamin that is produced by the body upon exposure of the skin to sunlight, but it can also be found in small amounts in certain foods such as oily fish. It plays a variety of roles in the body and over recent years our understanding of how it helps to maintain optimum health has dramatically increased. For example, it’s thought to reduce the risk of certain bone diseases, bacterial and viral infections and autoimmune diseases.
Interestingly, some studies have hinted that vitamin D may play a neuroprotective role. In support of this idea, several recent studies have found links between vitamin D deficiency and the risk of dementia and cognitive decline. However, one study also found no associations in men.
To find out more, an international team of researchers, headed by scientists at the University of Exeter, enrolled 1,658 adults aged 65 and over who were able to walk unaided and were free from dementia, cardiovascular disease and stroke. Vitamin D levels were assessed at the start of the study and the participants were then followed for six years in order to investigate who went on to develop Alzheimer’s or other forms of dementia.
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.
“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- we actually found that the association was twice as strong as we anticipated,” lead researcher Dr David Llewellyn said in a news-release.
He also said that trials are warranted in order to investigate whether vitamin D supplementation or eating foods containing vitamin D such as oily fish can delay or prevent the onset of dementia. However, he cautions that the study cannot definitively prove that low vitamin D levels cause dementia. Still, the results are encouraging, he said.
Dr Clare Walton, a researcher communications manager at Alzheimer’s Society, also warns about extrapolating from this kind of study. “A study like this can’t tell us whether being deficient in vitamin D can cause dementia. At the moment, we are still unclear how the two might be linked and there is even a possibility another unknown factor could cause someone to have both dementia and low vitamin D levels,” she told the BBC. However, she agrees that large clinical trials would be useful to find out whether increasing vitamin D levels can reduce dementia in the over 65s.
[Header image "I'll be losing my mind anyway," by John, via Flickr, used in accordance with CC BY-NC-SA 2.0]