Link between vitamin D, dementia risk confirmed
Vitamin D deficiency is
associated with a substantially increased risk of dementia and Alzheimer's
disease in older people, according to the most robust study of its kind ever
conducted.
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.
The team studied
elderly Americans who took part in the Cardiovascular Health Study. They
discovered that adults in the study who were moderately deficient in vitamin D
had a 53 per cent increased risk of developing dementia of any kind, and the
risk increased to 125 per cent in those who were severely deficient.
The study was
part-funded by the Alzheimer's Association, and is published inNeurology,
the medical journal of the American Academy of Neurology. It 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.
"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 by the
Alzheimer's Association, 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 the National Institute for Health Research
Collaboration for Leadership in Applied Research and Care South West Peninsula
(NIHR PenCLAHRC).
Dementia is one of the
greatest challenges of our time, with 44 million cases worldwide -- a number
expected to triple by 2050 as a result of rapid population aging. A billion
people worldwide are thought to have low vitamin D levels and many older adults
may experience poorer health as a result.
The research is the
first large study to investigate the relationship between vitamin D and
dementia risk where the diagnosis was made by an expert multidisciplinary team,
using a wide 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 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. In many countries the amount of UVB radiation in winter is too
low to allow vitamin D production.
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 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 this
hottest of summers, hitting the beach for just 15 minutes of sunshine is enough
to boost your vitamin D levels. However, we're not quite 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."
Story Source:
The above story is
based on materials provided
by University of Exeter. Note: Materials may be edited for
content and length.
Journal
Reference:
1.
Thomas J. Littlejohns, William E. Henley, Iain A. Lang, Cedric
Annweiler, Olivier Beauchet, Paulo H.m. Chaves, Linda Fried, Bryan R.
Kestenbaum, Lewis H. Kuller, Kenneth M. Langa, Oscar L. Lopez, Katarina Kos,
Maya Soni, and David J. Llewellyn. Vitamin
D and the risk of dementia and Alzheimer disease.Neurology,
August 2014 DOI: 10.1212/WNL.0000000000000755
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University of Exeter.
"Link between vitamin D, dementia risk confirmed." Science
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