A deficiency of vitamin D in older persons may double the risk of developing dementia and Alzheimer’s disease, according to results of a new study.
Dementia is broadly characterized by a decline in thinking and memory. Alzheimer’s disease, which affects about 5 million people in the US, is the most common type of dementia associated with aging. And with the aging baby boomer population, the number of people living with Alzheimer’s is expected to increase nearly three fold by 2050.
The study was published online in the Journal Neurology, August 6, 2014.
Researchers evaluated levels of vitamin D in the bloodstream, reflected by dietary intake of vitamin D, sun exposure, as well as use of supplements. Vitamin D is contained in eggs, milk and cheese, as well as in fatty fish such as tuna, mackerel, and salmon.
“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,” said study author David J. Llewellyn, PhD, of the University of Exeter Medical School in England.
The study evaluated vitamin D levels in 1,658 healthy people age 65 and older without dementia. Six years later, 171 persons in the study developed dementia and 102 had Alzheimer’s disease.
According to the results of the study, persons with low levels of vitamin D had a 53-percent increased risk of developing dementia. Persons who had a more significant deficiency had a 125 percent increased risk of developing dementia compared to participants with normal levels of vitamin D.
Those persons with lower levels of vitamin D were almost 70 percent more likely to develop Alzheimer’s disease and those who had severe deficiency were over 120 percent more likely to develop Alzheimer’s disease.
The results were unchanged after researchers adjusted for factors that could affect risk of dementia, such as smoking, alcohol use, as well as education.
"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,” explained Llewellyn.
However, Llewellyn was careful about the implications regarding the findings of this study.
“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.”
Dr. Gayatri Devi, a neurologist at Lenox Hill Hospital in New York City specializing in memory disorders believes that a multifaceted approach to Alzheimer’s disease and dementia is vital to effect a broader understanding of the condition.
“Alzheimer's disease, which occurs later in life, is an illness caused by a multitude of factors including diet, lifestyle, as well as genetics,” explained Devi.
“This study points to the importance of good levels of vitamin D in helping to prevent onset of Alzheimer's disease in late life, the most common type of Alzheimer's,” said Devi. “Vitamin D helps to prevent the accumulation of the toxic amyloid plaque that is present in Alzheimer's disease and prevents vascular brain disease.”
Devi summarized her beliefs about Vitamin D this way:
“Good levels of vitamin D, which are found in a healthy diet, help to maintain neuronal health and vibrancy of the brain, and point to the importance of a multifaceted approach to preventing Alzheimer's disease that embraces diet, exercise and other lifestyle modifications in addition to reducing genetic risk.”
