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Health December 2014

Aid for Age

Risk of Dementia and Alzheimer’s Much Reduced by Vitamin D

By Tait Trussell

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 deficiency can substantially increase the risk of dementia and Alzheimer's disease in older people. The risk is twice — yes, twice – as great as scientists had expected.

This important finding by an international team of doctors was led by Dr. David Llewellyn at the University of Exeter Medical School in southwest England. It discovered that study participants who were severely Vitamin D deficient were more than twice as likely to develop dementia and Alzheimer's disease.

Specifically, the team determined elderly Americans who took part in the cardiovascular study who were moderately deficient in vitamin D had a 53 per cent increased risk of developing dementia of any kind. Strikingly, the risk increased to 125 per cent in those who were severely deficient in Vitamin D.

Similar results were found for Alzheimer's disease; with the moderately deficient group 69 per cent more likely to develop this type of dementia, jumping to a 122 per cent increased risk for those severely deficient in Vitamin D.

The study was partially funded by the Alzheimer's Association and the results were published in Neurology, the medical journal of the American Academy of Neurology.

The scientists examined 1,658 adults aged 65 and over, who were able to walk unaided and were free of 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.

"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."

Research collaborators included experts from Angers University Hospital, Florida International University, Columbia University, the University of Washington, the University of Pittsburg and the University of Michigan.

The study was supported, in addition to the Alzheimer's Association, by the Mary Kinross Charitable Trust, the James Tudor Foundation, the Halpin Trust, the Age Related Diseases and Health Trust, the Norman Family Charitable Trust, and other organizations.

The vitamin D and dementia risk, where the diagnosis was made by an expert multidisciplinary team used a broad range of information including neuroimaging. 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 three main sources – exposure of our skin to sunlight; foods such as oily fish and bananas; and vitamin supplements. Older people's skin can be less efficient at converting sunlight into Vitamin D, making us elders more likely to be deficient and reliant on other sources. In many countries the amount of UVB (radiation ultraviolet B shortwave rays) in winter is too low to allow vitamin D production.

Vitamin D is a fat-soluble vitamin, according to the National Institutes of Health. It is naturally present in few foods, but available as a dietary supplement. To get technical, it is produced endogenously (from within) when ultraviolet rays from sunlight strike the skin and trigger vitamin D synthesis. Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations (oxidative processes) in the body for activation.

The multi-organization 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 measurement might lie in the region of 25-50 nmol/L. Their new findings confirm that vitamin D levels above 50 nmol/L are most strongly associated with good brain health.

Commenting on the study, Dr. Doug Brown, Director of Research and Development at Alzheimer's Society said: "Shedding light on risk factors for dementia is one of the most important tasks facing today's health researchers. While earlier studies have suggested that a lack of the sunshine vitamin is linked to an increased risk of Alzheimer's disease, this study found that people with very low vitamin D levels were more than twice as likely to develop any kind of dementia.

During the heat of summers, hitting the beach for just 15 minutes of sunshine is enough to boost your vitamin D levels. However, scientists aren’t ready to say that sunlight or vitamin D supplements will reduce your risk of dementia. Large scale clinical trials are needed to determine whether increasing vitamin D levels in those with deficiencies can help prevent the dementia from developing.

 

Tait Trussell is an old guy and fourth-generation professional journalist who writes extensively about aging issues among a myriad of diverse topics.

Meet Tait