Vitamin D deficiency is associated with a substantially increased risk of dementia and Alzheimer’s in older people, according to the most robust study of its kind ever conducted.
An international team, led by David Llewellyn at the University of Exeter Medical School, found those who are severely Vitamin D deficient are more than twice as likely to develop dementia and Alzheimer’s disease.
The team studied elderly Americans who took part in the Cardiovascular Health Study. Adults in the study 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, published in the journal Neurology, the medical journal of the American Academy of Neurology, looked at 1,658 adults aged 65 and over, 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.
Dr Llewellyn said:
“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.”
He said 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,” hew said.
“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.”
There 44 million cases of dementia worldwide and this is expected to triple by 2050 as a result of rapid population ageing.
A billion people worldwide are thought to have low vitamin D levels and many older adults may experience poorer health as a result.
Previous research established that people with low vitamin D levels are more likely to go on to experience cognitive problems, but this study confirms that this translates into a substantial increase in the risk of Alzheimer’s disease and dementia.
Vitamin D comes from exposure of skin to sunlight, foods such as oily fish and supplements.
Older people’s skin can be less efficient at converting sunlight into Vitamin D, making them more likely to be deficient and reliant on other sources.
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