A new study confirms that older adults who don’t get enough of the essential nutrient vitamin D could double their risk of dementia or Alzheimer's disease.

The study, published in Neurologyexamined blood tests from 1,658 people over the age of 65. None of the volunteers had dementia. After about six years, 171 of them developed dementia and 102 were diagnosed with Alzheimer's disease.

"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," study author David J. Llewellyn of the University of Exeter Medical School in the U.K. said in a press statement.

Compared to people with normal levels of vitamin D, those with low levels had a 53 percent increased risk for dementia and were 70 percent more likely to develop Alzheimer's. Those who were severely deficient in vitamin D had a 125 percent greater risk for dementia and were more than 120 percent more likely to get Alzheimer's.

The results were the same after the researchers adjusted their numbers to take other risk factors like smoking, alcohol consumption, and education level into account.

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Can Vitamin D Prevent Dementia?

Llewellyn said more clinical trials should be conducted to test whether eating foods high in vitamin D or taking vitamin D supplements could delay or even prevent dementia and Alzheimer's.

“Given that there are currently no disease modifying treatments for dementia this is an important area for future research,” said Llewellyn, who explained that the research is at an early stage and does not demonstrate that low vitamin D levels cause dementia — it just links the two conditions. “Even if a small number of people could benefit, this would have enormous public health implications given the devastating and costly nature of dementia,” he said.

Llewellyn said it’s too early to know if boosting vitamin D levels could delay or prevent dementia, but past trials have shown that it is effective for other health issues, such as preventing bone fractures.

“People should eat a balanced diet including oily fish and regularly venture outdoors as part of an active lifestyle, which includes moderate intensity exercise such as brisk walking,” he said.

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The Link Between Depression, Dementia

A new study from Rush University Medical Center, also published in Neurology, found that people with depression have a greater risk of developing dementia as well.

Researchers studied 1,764 people for about eight years. The volunteers had no memory problems at the start of the study. The researchers found that people who were later diagnosed with dementia or mild cognitive impairment — often an early sign of Alzheimer's disease — were more likely to have had higher levels of depression before their diagnosis. The researchers also linked higher levels of depression to a faster decline in memory.

"These findings are exciting because they suggest depression truly is a risk factor for dementia, and if we can target and prevent or treat depression and causes of stress we may have the potential to help people maintain their thinking and memory abilities into old age," lead researcher Robert S. Wilson, a neuropsychologist at the Rush Alzheimer's Disease Center, said in a press statement.

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