Do Elevated Homocysteine Levels Increase Risk For Alzheimer's Disease?

Like many people, you may be asking "what is homocysteine" and wondering how it could increase your risk of having Alzheimer's Disease. Homocysteine is an amino acid produced naturally by the body, but too much homocysteine in the blood is toxic and can lead to damage and blockage of the arteries and blood vessels.

This makes elevated homocysteine levels a risk factor for vascular disease like heart disease and stroke. During the last ten years research has revealed a possible connection between vascular disease and the Alzheimer's Disease and other kinds of dementia. "The New England Journal of Medicine" recently published a study that indicates that elevated levels of homocysteine may itself may increase older people's risk of Alzheimer's Disease and other forms of dementia.

About the study:
A group of researchers at Boston University and Tufts University in Boston began studying a subgroup of participants of the Framingham Study during the period between 1986 and 1990.

The Framingham Study participants had been having complete physical exams and answering lifestyle questionnaires every two years since 1948. The subgroup was comprised of 1,092 men and women with an average age of 76. Participants in the subgroup were all free of any dementia at their 20th biennial exam. These occurred between the years 1986 and 1990. Blood homocysteine levels were checked at both the 20th and 16th biennial exams,

Participants of the subgroup underwent additional tests beyond those required by the Framingham Study protocol. Each participant of the subgroup had tests for dementia during the biennial exam from 1986 to December 2000. The results were evaluated by two neurologists and a neuropsychologist. Each participant was also tested for an apolipoprotein E gene - a known risk factor for Alzheimer's Disease.

The participant's medical records were reviewed by researchers form their 20th biennial exam through December 2000 along with their homocysteine measurements recorded from their 16th biennial exam. They were specifically looking at how homocysteine blood levels correlated with Alzheimer's Disease or other dementia.

Research findings:
It was found that an increase of 5 micromoles of homocysteine per liter of blood increased the risk of Alzheimer's Disease by 40%. People with the highest levels of blood homocysteine had almost double the risk of Alzheimer's and other dementia as compared to people with lower blood homocysteine. This determination was made after accounting for other risk factors.

It is important to note that the statistics held true for homocysteine levels from both the 16th and 20th biennial exams. Since Alzheimer's Disease develops slowly, it may be the disease process had begun in some study participants at the 20th biennial exam but was not yet measurable. It would be very unlikely the participants were really free of disease at the 16th biennial exam, eight years prior.

What does this mean to you?
We do know that elevated homocysteine levels may increase the risk of heart disease and stroke. The study finding now suggest that elevated homocysteine levels may also increase our risk of Alzheimer's Disease and other conditions of dementia as we age. However, they didn't go as far as proving elevated homocysteine levels an indicator of future Alzheimer's Disease. The participants age ranged from 68 years to 97 years which makes it unclear whether younger adults might be at increased risk of Alzheimer's later in life if they have elevated homocysteine levels.

Having said that, several other studies do suggest that keeping homocysteine levels in check may help prevent blood vessel damage and prevent atherosclerosis (hardening of the arteries). The good news is that it is easy to keep your homocysteine levels in the safe range.

Vitamin B-12, folic acid and vitamin B-6 when taken in food or supplements has been shown to reduce homocysteine levels in the blood. Although we don't yet know if this will also reduce the risk of Alzheimer's Disease, the known benefits make it worthwhile to make sure you obtain adequate supplies of these nutrients through diet and supplementation.
Foods containing folic acid include:

* Fruits and orange juice from concentrate
* Green, leafy vegetables
* Dried beans and legumes
* Liver
* Grain products that have been fortified with folic acid, such as cereal, pasta, rice, and bread

Foods containing Vitamin B-12 include:

* Liver and other meats such as pork and beef
* Eggs
* Milk and other milk products

Vegetarians should note: they must supplement to get their vitamin B-12 as fruits and vegetables contain no vitamin B-12.

REFERENCES:
Seshadri S, et al. "Plasma homocysteine as a risk factor for dementia and Alzheimer's Disease", "New England Journal of Medicine", February 14, 2002;346(7):476-483.
Loscalzo J., "Homocysteine and dementias", "New England Journal of Medicine", February 14, 2002;346(7):466-468.

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