Researchers study alcohol's link to Alzheimer's
Nearly one century after Alzheimer's disease (AD) was discovered, doctors are still
searching for its causes. Age is certainly a factor: Alzheimer's usually develops in people
over age 60, and about half of people over 85 may have it. Family history also plays a role.
Now researchers are considering another possible risk factor: alcohol use. And the clues start with physical changes to the brain.
In 1906, Alois Alzheimer, a German physician, did an autopsy on a woman who died of a mysterious mental illness. When he examined the womans brain, he found abnormal clumps of tissue and a tangled maze of nerve fibers.
Today these two symptoms--amyloid plaques and neurofibrillary tangles--remain defining marks of Alzheimer's disease. So is shrinkage of the brain and dementia (mental deterioration).
Long-term alcoholism can also shrink the brain and lead to dementia. For example, some of the heaviest drinkers develop a form of brain damage called Wernicke-Korsakoff syndrome. People with this syndrome suffer a severe loss of short-term memory. They can remember events that happened before the syndrome kicked in, but they often forget new information within a few seconds.
In addition to brain shrinkage and memory loss, both Alzheimer's and alcoholism can interfere with neurotransmitters--the chemical messengers that travel between brain cells. And both conditions can lead to profound personality changes over time.
Given the similar effects of alcoholism and Alzheimer's, it is logical for scientists to look for a link between them. However, the alcohol-Alzheimer's connection remains elusive, notes Suzanne Tyas, Ph.D., in an article published last year in Alcohol Research & Health (Vol. 25, No. 4). Tyas, a gerontologist at the University of Kentucky in Lexington, writes that some research findings even argue against the connection.
For instance, people with Alzheimer's disease usually experience an irreversible decline in mental ability. This is not always true for recovering alcoholics who succeed at staying sober. In fact, years of abstinence from alcohol may lead to recovery of mental ability. Tyas cites a study where researchers compared the number of nerve cells in brains of alcoholics and non-alcoholics and found no significant differences. Alcoholics did lose other kinds of cells in the brain that support the work of nerve cells. But these support cells can be regenerated, leading to gains in mental function.
Also, researchers cannot point to a one-to-one relationship between alcoholism and mental decline. Long-term alcoholics may not lose mental function. Some researchers even found that alcohol use lowered risks for Alzheimer's.
Finally, a high percentage of alcoholics use tobacco, and nicotine can counteract the negative effects of alcohol on mental ability, including increased reaction time. Of course, this is no argument in favor tobacco use--a habit that contributes to over 400,000 deaths annually in the United States. Plus, research shows that alcohol and tobacco use interact to influence the risk of certain diseases, such as cancer.
So far, then, we cannot say that alcohol use increases the risk of Alzheimer's. But this conclusion may change as researchers find better ways to distinguish between alcoholic dementia and Alzheimer's. Perhaps alcoholic dementia and Alzheimer's are both caused by similar factors that are yet to be discovered.
The heavy stakes of Alzheimer's give researchers an incentive to keep investigating an alcohol-Alzheimer's connection. Alzheimer's disease is the leading cause of dementia in the United States, and the number of Americans with Alzheimer's could quadruple within 50 years, unless we find ways to prevent it.
Alcohol use is a behavior that people can change, and treatment for addiction can lead recovering alcoholics to life-long sobriety. If alcohol use does contribute to Alzheimer's, then some day we can apply our knowledge of preventing alcoholism to preventing Alzheimer's.