March 11, 2005

AMARILLO – More than 4 million Americans have Alzheimer's disease, but few people can tell you much about the devastating illness.

Alzheimer's is a chronic, degenerative disease, which slowly gets worse as it progresses, said Andrew B. Crocker, Texas Cooperative Extension gerontology health specialist.

While most Americans assume the majority of Alzheimer's patients reside in nursing homes, Crocker said close to half of them actually reside at home.

By 2050, more than 14 million Americans are expected to be diagnosed with the disease.

"It seems that the incidence of Alzheimer's disease has increased in recent years to near epidemic proportions," Crocker said. "While improvement in diagnosis has contributed to the rise, the real answer lies in the average length of life for human beings."

In the 18th century, the average lifespan was 35 to 40 years. Now, the average lifespan in the United States is about 77 years. Studies show about 10 percent of those over age 65, 20 percent of those over 77 and half of those over 85 have Alzheimer's.

"Alzheimer's is more prevalent now because more and more people are living long enough to develop the disease," Crocker said.

Plaque is a major part of the disease process.

"We normally associate the word plaque with an award or something that our dentist warns us about when we go in for a check-up. This particular type of plaque forms in the brain between nerve cells, causing nerve signals in the brain to be interrupted," Crocker said.

Nerve cells are like electric lines that transmit signals back and forth. If a piece of insulation blocks the electricity put in the line, the signal can not get through. Crocker said that is how plaque affects the brain – it prevents brain signals from getting from one place to another.

Plaque is made up of a protein the body produces normally. In a normal brain, the protein is eliminated. In the Alzheimer patient's brain, the protein clumps together with other pieces and forms a plaque.

Another hallmark of Alzheimer's is the formation of tangles, Crocker said. Imagine the nerve cells in the brain are like railroad tracks, with two side pieces and a ladder-like structure in the middle holding everything in place.

These ladder-like structures are made up of a protein that becomes abnormal in the Alzheimer patient's brain and causes the ladder to weaken and collapse. If enough proteins become abnormal, the whole nerve cell may collapse on itself and prevent nerve signals from being transmitted, he said.

Alzheimer's begins its destruction in the hippocampus, the part of the brain responsible for taking in new information and processing it through the memory. As the disease spreads, it works its way through the outer layers of the brain, affecting judgment, emotions and language.

Eventually, enough of the brain is overrun by plaque and tangles that even the most basic functions are impaired, such as the ability to use the toilet, communicate and walk. The disease completely destroys an individual's ability to be independent and a state of dependency may last for years.

"The average length of time from diagnosis of Alzheimer's disease to death is three to 10 years, though disease progression may take as long as 20 years," Crocker said.

The only way to make a 100 percent certain diagnosis of Alzheimer's is an autopsy of the brain upon death, he said. However, medical science has progressed such that mental tests, physical exams and ruling out other illnesses can help make a 90 percent-certain diagnosis.

Early diagnosis is important so prescription drug therapy may be started, Crocker said. Though there is no cure for Alzheimer's, medications may help control the symptoms and slow the disease progression.

Testing and diagnosis by a trained health professional is very important since other conditions may resemble Alzheimer's disease, Crocker said. These other conditions may be treatable or completely reversible.

For more information, contact your county Extension agent or go to the Alzheimer's Association Web site at http://www.alz.org. The Alzheimer's Association may also be contacted at (800) 272 3900.