Cardiovascular Disease And Its Risk Factors - Causes Of Memory Impairment: Improving Memory Understanding Age Related Memory Loss

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Cardiovascular disease and its risk factors

Physicians and neuroscientists now know that what's bad for the heart is also bad for the brain. Conditions that have been linked with heart disease — high blood pressure, high cholesterol, and diabetes — have also been linked to memory problems.

Hypertension

Adults with high blood pressure (hypertension) are more prone to memory impairment than people with normal blood pressure. Moreover, people with hypertension experience memory losses that are more severe than those suffered by individuals who don't have hypertension. These differences hold true regardless of age.

Hypertension may impair memory by damaging the brain's white matter, the bundles of axons that transmit messages throughout the brain and central nervous system. Changes in white matter occur to some degree in virtually everyone over age 60 and contribute to normal age-related memory loss. But damage to white matter is especially prevalent among people with hypertension, according to a 2003 report in the journal Psychology and Aging. In this study, people with the most extensive white-matter abnormalities performed worst on tests of memory, learning, and other mental functions.

Some research suggests that untreated — or inadequately treated — hypertension predisposes a person to dementia. Brain-imaging studies suggest that increased blood pressure can cause small strokes that damage the brain (see "Cerebrovascular disease and stroke"). In addition, hypertension increases the risk for heart disease. One common treatment for heart disease, coronary artery bypass surgery, can itself cause neurological problems that impair memory.

Physicians believe that lowering blood pressure may help preserve memory and other aspects of cognitive function well into old age. But be aware that one class of hypertension drugs, the beta blockers, can temporarily impair memory (see "Medications"). If you experience memory impairment while taking a beta blocker, replacing the drug with a different blood pressure medicine may restore memory function to normal within several days.

High cholesterol

In contrast to hypertension, which can cause memory problems fairly quickly after it develops, high cholesterol appears to increase the risk for mild cognitive impairment and Alzheimer's disease many years down the road. People with high cholesterol have a higher than average incidence of these two conditions. It's not clear how high cholesterol might lead to memory loss, or whether the crucial factor is excessive low-density lipoproteins (LDL, the "bad" cholesterol) or insufficient high-density lipoproteins (HDL, the "good" cholesterol).

Some studies suggest that people who are treated with statins, a class of cholesterol-lowering medications, reap the additional benefit of decreasing their risk of Alzheimer's disease and mild cognitive impairment. Other studies suggest that statins can help treat dementia. Some specialists believe that giving statins to people with high cholesterol may reduce their risk of developing dementia. Although a large study published in Archives of Neurology in 2005 failed to show a relationship between statin use and dementia risk, the study was not definitive. More research is needed to find out whether statins have a role in preventing memory disorders.

Diabetes

Two features of diabetes can impair memory. High blood sugar, the hallmark of the disease, depresses the function of the hippocampus. Middle-aged and elderly people with high blood sugar are likely to have a smaller hippocampus than younger adults, according to a 2003 report in the Proceedings of the National Academy of Sciences.

The other feature of diabetes that can harm memory is high levels of insulin, the hormone that transports sugar from the blood into the body's cells. According to a study in Archives of Neurology in 2005, even moderately high insulin levels increase biochemical markers for inflammation, which is thought to promote Alzheimer's disease. For the study, in which researchers raised insulin levels of 16 adults ages 55–81, elevated insulin also led to an increase in blood levels of beta-amyloid, the sticky substance that degrades brain function in Alzheimer's disease.

Insulin injections, needed by many people who have diabetes, can cause memory loss, too, but the memory loss associated with untreated diabetes is far more severe.

Coronary artery bypass surgery

Both memory loss and diminished attention are prevalent among people who have had coronary artery bypass surgery to treat blocked arteries. These symptoms usually subside after a few months, but some people end up with more permanent cognitive dysfunction. This trouble has led to concern that the use of a heart-lung pump during bypass surgery damages the brain. The results of studies on this topic have been mixed. Older studies have shown some effects that persist five years after bypass surgery, but more recent research has found that the problem is temporary, if it exists at all.

A study published in Annals of Thoracic Surgery in 2003 found that more than two-thirds of people had impaired memory as well as difficulty thinking and learning in the weeks following the surgery, but three months later, their minds were as sharp as they had been before. A year-long study published in Neurology in 2005 found no significant difference in memory and related test scores between people who had coronary bypass surgery (with or without a heart pump) and people with heart disease who did not have bypass surgery. Improvements in surgical techniques might explain these more hopeful findings.

Last updated:	January 23, 2007