Older
adults who are severely deficient in vitamin D may be more than twice
as likely to develop dementia or Alzheimer’s disease than those who
don’t have a deficiency, according to the largest
study of its kind, published Wednesday in the journal Neurology.
“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,” noted lead
researcher David Llewellyn of the University of Exeter Medical School
in a
news release.
Llewellyn, who could not be
reached for comment by Yahoo Health, looked at several years worth of
data on 1,658 Americans ages 65 and older who had taken part in the
National Heart, Blood and Lung Institute’s
Cardiovascular Health Study.
He and his team found that adults who were just moderately deficient in
vitamin D had a 53 percent increased risk of developing dementia — the
general term for any severe decline in mental ability — while the risk
jumped to 125 percent for those who had a severe deficiency. Similarly,
for Alzheimer’s disease — the most common type of dementia — the
moderately deficient adults were 69 percent more likely to develop it,
while the severely deficient had a 122 percent increased risk.
“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,” Llewellyn said. “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.”
Currently, more than five million
Americans are living with Alzheimer’s disease, which is the sixth
leading cause of death in this country, according to the Chicago-based
Alzheimer’s Association.
One in three seniors dies with Alzheimer’s or another form of dementia.
“We think this study is important,” Keith Fargo, director of scientific
programs and outreach with the Alzheimer’s Association (a major funder
of Llewellyn’s research), told Yahoo Health in response to the findings.
“It’s a relatively large study, and it looks like it does show a pretty
substantial link.… It just doesn’t show us why there is a link.” One
hypothesis, Fargo noted, is that the brain — including the hippocampus,
which is one of the first areas to break down with Alzheimer’s — is full
of vitamin D receptors.
There
has been a growing body of research on the disease’s connection with
vitamin D — the main sources of which are sunshine and supplements, with
minor sources including egg yolks and oily fish like salmon and
sardines. Earlier this year, a
study out
of Denmark, for example, also showed a link between Alzheimer’s disease
prevalence and low levels of vitamin D, while earlier studies conducted
in
Australia and
France found tenuous connections between taking doses of vitamin D and
having an improved memory. The vitamin has also been linked, in various
studies, to preventing asthma, diabetes, and cancer.
“People tend to not believe
vitamin D news, because it seems too good to be true,” John Cannell, MD,
executive director of the California-based nonprofit
Vitamin D Council,
told Yahoo Health. “But vitamin D has a profound mechanism of action,
as it’s really a steroid hormone that turns genes on and off, and no
other vitamin works that way. There are at least 1,000 different genes
directly influenced by vitamin D.” The council recommends a combination
of cautious sun exposure combined with supplements in winter months.
Cannell called the new study’s
findings “pretty exciting,” mainly because of its size and structure.
“It’s important because it’s the first cohort study of a large
population — meaning that it’s forward-looking, having followed people
over several years,” he said. “The next step is a randomized controlled
trial, but this is as close as you can get without that.”
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