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.
Similar results were recorded 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.
The study was part-funded by the Alzheimer's Association, and is published in Neurology, 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."
Journal Reference:
- 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
Courtesy: ScienceDaily
No comments:
Post a Comment