[6]Photo by Colin Dunn, CC-BY-2.0, via flickr
The journal Neurology published an article [7] describing the results of a study that confirmed a strong association between low levels of vitamin D and increased risk of dementia and Alzheimer’s disease in elderly people in the U.S. Here’s a breakdown of the research.
Background
There is a lot of interest in understanding the impact of vitamin D levels in people with Alzheimer’s disease and other dementias. First off, vitamin D production occurs in several brain regions and there are vitamin D receptors throughout the brain, including the hippocampus, which is an important brain region for memory function. Vitamin D has been linked to clearance of amyloid plaques and to inflammatory processes in the brain related to amyloid. Vitamin D has also been linked to problems with blood vessels in the brain and other cerebrovascular pathology, which may be related to Alzheimer’s. Lastly, high rates of vitamin D deficiency are seen older adults.
The main sources of vitamin D are exposure of skin to sunlight; foods such as fatty fish (salmon, tuna), egg yolks, beef or calf liver and cheese; and dietary supplements. Vitamin D levels are easily evaluated through a standard blood draw done in a doctor’s office, similar to cholesterol tests.
The claim
Vitamin D deficiency is associated with a substantially increased risk of all-cause dementia and Alzheimer’s.
The methodology
This observational study looked at vitamin D levels in 1,658 people age 65+ who were free from dementia, cardiovascular disease, and stroke when they submitted blood samples for the Cardiovascular Health Study between 1992-1993 and 1999. The study participants were later tested for levels of vitamin D and evaluated for Alzheimer’s disease and other dementias.
- During the study, 171 participants developed dementia, including 102 cases of Alzheimer’s.
- Compared to participants with normal levels of vitamin D, those with low levels of vitamin D had a 53% increased risk of developing dementia, and those severely deficient of vitamin D had a 125% increased risk.
- Those with low levels of vitamin D had a 69% increased risk of Alzheimer’s; those severely deficient had a 122% increased risk of Alzheimer’s.
Beyond the headline
Although this is not a new finding, the study does offer large-scale confirmation of a known association between vitamin D and dementia. It is important to note, however, that the study shows a correlation between vitamin D levels and Alzheimer’s disease and dementia; it does not show that low levels of vitamin D causes Alzheimer’s or dementia. It may be that having dementia causes vitamin D levels to go down, or there may be a third factor that affects both vitamin D levels and dementia risk. Observational studies such as this one uncover these associations, which then can be investigated further in other kinds of research, such as clinical trials.
The bottom line
It would be wonderful if addressing a single issue like vitamin D deficiency could delay or prevent Alzheimer’s disease. It would be simple, inexpensive, alleviate much suffering and heartache, and greatly reduce healthcare costs. However, Alzheimer’s and other brain diseases are very complex, and it will most likely require a combination of factors to influence your risk for dementia.
As a next step in the scientific process, we’d like to see clinical trials – where levels of vitamin D are changed in one study group but not in another – to investigate whether increasing vitamin D in people with low levels can delay or prevent Alzheimer’s.
The Alzheimer’s Association is pleased to have provided funding for this research and look forward to seeing more studies on vitamin D that will further our understanding of its relationship to Alzheimer’s disease.
Helpful information related to this story
More research stories by Dr. Edgerly [8]
Read the article in [7]Neurology [7]
The Alzheimer’s Association’s Research page [9]
Alzheimer’s disease risk factors [10]