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Thursday, August 07, 2014

Can Vitamin D Affect the Risk of Alzheimer's?


Dear Readers,

A few years ago, (July 2010), I wrote about a study that raised the possibility of a relationship between vitamin D and Alzheimer’s disease (AD). In that study, researchers reported a possible link between vitamin D deficiency and an increased risk of cognitive impairment and dementia later in life. They had analyzed data from 3,325 people aged 65 and older who lived in Tuscany, Italy over a period of six years. They measured the participants’ vitamin D levels from blood samples, and compared them with their performance on cognitive function measures such as memory tests, orientation in time and space, and ability to maintain attention. Those who scored in the lowest 10 percent were classified as being cognitively impaired. The study found that the risk of cognitive impairment was 42 percent higher in people who were vitamin D deficient, and 394 percent higher in those with severe vitamin D deficiency. This association remained after adjusting for potential confounders.

Now, researchers in the United Kingdom report that individuals with a moderate vitamin D deficiency have about a 50 percent higher risk of some form of dementia, including Alzheimer’s dementia, and a doubling of their increased risk of AD if they are severely deficient.

The researchers analyzed data from a study of vitamin D blood levels in 1,658 people age 65 and older who were cognitively normal. They were followed for about six years, using MRI brain imaging and cognitive tests. The researchers also report that the risk of dementia appears to be significantly increased in people with vitamin D blood levels below 25 nanomoles per liter, while vitamin D levels above 50 nanomoles appear to lead to a reduced risk.

Vitamin D is a steroid hormone that is involved in bone health, but also acts in the brain. Vitamin D deficiency is common in the elderly because of the skin’s reduced capacity to synthesize it with age and because of decreased sun exposure, which is necessary for the synthesis of the vitamin.

Still more work is needed to look at vitamin D and any direct effects on AD risk. For example, could it be possible that there is a reciprocal relationship, that is, could very mild AD lead to dietary changes or diminished outdoor activities that then leads to less sun exposure and hence lower vitamin D levels? It is still recommended that anyone who is considering changing their diet to include vitamin supplements, but before doing so, should speak to their doctor. These vitamin D findings need to be replicated in placebo controlled studies before such recommendations can be made.




Thanks for reading,


Michael Rafii, MD, PhD
Director, Memory Disorders Clinic
Medical Core Director
Alzheimer’s Disease Cooperative Study
University of California San Diego
 
Author: Michael Rafii MD, PhD at 9:37 AM 0 Comments

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The Alzheimer's Disease Cooperative Study (ADCS) was formed in 1991 as a cooperative agreement between the National Institute on Aging (NIA) and the University of California, San Diego. The ADCS is a major initiative for Alzheimer's disease (AD) clinical studies in the Federal government, addressing treatments for both cognitive and behavioral symptoms. This is part of the NIA Division of Neuroscience's effort to facilitate the discovery, development and testing of new drugs for the treatment of AD and also is part of the Alzheimer's Disease Prevention Initiative.

The ADCS was developed in response to a perceived need to advance research in the development of drugs that might be useful for treating patients with Alzheimer's disease (AD), particularly drugs that might not be developed by industry.