September 13, 2004
High levels of homocysteine, an amino acid-like substance that circulates in the blood, may be an early risk factor for memory problems and Alzheimer's disease, researchers report. The findings come from a study in Australia of nearly 400 healthy middle-aged adults who had no obvious signs of memory loss or dementia.
Like cholesterol, high levels of homocysteine have been linked to an increased risk of heart attacks, strokes, and blood vessel disease. Scientists have focused increasing attention on the substance in recent years as a possible marker for heart disease, Alzheimer's, and other diseases of aging.
In the current study, which appeared in the September 2004 issue of the medical journal Archives of Neurology, researchers from the University of New South Wales in Sydney enlisted 196 men and 189 women aged 60 to 64. All were given blood tests to measure levels of homocysteine, and about 15 percent were found to have high levels of the substance. Scanning tests were also done to look for areas of the brain that may be abnormal, and study participants were given tests to measure verbal memory, fine motor speed, and the speed with which they processed information. Other factors that may also contribute to heart and brain health were also taken into consideration, including high blood pressure, diabetes, whether or not somebody smokes, and overall physical health.
Interestingly, men (but not women) with high levels of homocysteine in the blood were found to have areas of damage deep in the brain. Those men with high homocysteine also had impairments in verbal memory and fine motor speed. The researchers concluded that high homocysteine levels may be linked to mild cognitive impairment, a milder form of age-related memory loss that may progress to Alzheimer's disease. They are not sure why their findings did not also apply to women, but called for additional research.
Previous studies have linked high homocysteine levels to an increased risk of heart attacks and strokes, as well as a possible increased risk of Alzheimer's disease. The substance seems to increase risk of damage to blood vessels throughout the body, including the brain. Damage to blood vessels in the brain may impede blood flow and oxygen supply, increasing the risk of memory problems and, eventually, Alzheimer's disease. Once again scientists are discovering that risk factors for heart disease are also risk factors for Alzheimer's. The reasons for this connection are not yet understood.
Earlier research had also suggested that high homocysteine levels may be related to "atrophy" or shrinkage of the brain in elderly men and women (over age 70). Although the scientists did not find any shrinkage in the brains of the patients in the current study, they did find areas deep in the brain that appeared damaged. They suspect that because the patients they studied were younger, in their early 60s, the brain damage they saw was still at an early, subtle stage.
Although the link between homocysteine and Alzheimer's remains unproven, the investigators believe that steps to lower blood homocysteine levels should begin early, before damage to the brain or blood vessels occurs. Homocysteine tests are not routinely performed, and most doctors do not recommend them as part of a regular medical check-up. But if you are over 60 and concerned about heart disease or Alzheimer's, you can ask your doctor to check your homocysteine levels.
In the meantime, Alzheimer's prevention may begin with such simple measures as a heart-healthy diet and taking a daily multivitamin. High homocysteine has been linked to deficiencies in two common B vitamins, vitamin B-12 and folic acid. Eating a diet rich in these nutrients such as a diet rich in animal protein, whole grains, leafy greens, and fruits has been shown to be an effective measure to help reduce homocysteine build-up. Many physicians recommend taking a supplement of 400 micrograms of folic acid per day, which can effectively lower homocysteine levels, as part of a heart-healthy program. Daily multivitamins also supply B vitamins and are particularly important for older individuals, who may not absorb vitamins and minerals as readily as younger persons.
Perminder Sachdev, MD, Phd, et al: "Homocysteine and the Brain in Midadult Life: Evidence for an Increased Risk of Leukoaraiosis in Men." Archives of Neurology, Vol 61, September 2004, pages 1369 - 1376.