What is Alzheimer's disease? A medical definition

Dr. Mike Breiner, a retired cardiologist from Grand Island, heard the best explanation of what Alzheimer's disease does to the body from a member of a support group he runs.

"She said it's like a forest fire of the brain," Breiner said. "That hit the nail on the head. That's exactly what it is."

The effects of Alzheimer's can often be mystifying for people to comprehend, but looking at the disease itself can prove helpful. According to the Mayo Clinic, Alzheimer's disease is:
"...the most common cause of dementia. It primarily affects adults in their 60s or older. Its development is unrelenting and irreversible." While the exact cause of the disease is not known, Alzheimer's begins by destroying the brain at its most basic structure -- the neuron.

It kills these cells in two major ways, through amyloid plaques inside the neuron, which kill it outright, and through neurofibrillary tangles, which cause the protein tau in the brain to twist, killing the neuron.

The hippocampus, the part of the brain that controls memory, is the first major area attacked by the disease but by no means the last. As the disease spreads to the frontal, parietal and temporal lobes of the cerebral cortex, the patient exhibits more and more symptoms. The only way to be sure of Alzheimer's disease is by brain autopsy. That is to say, a diagnosis can never be sure until a person is dead.

That being said, imaging technology coupled with symptoms can lead to accurate diagnoses. Currently, between 4 million and 5 million Americans have the disease, including about 40,000 in Nebraska. With the aging of the United States, those numbers are set to skyrocket in the next decade.

Dr. Ahmed Sadek, a neurologist at St. Francis Medical Center, said Alzheimer's is the most prevalent of dementias but might not be the only dementia a person with Alzheimer's can have. Anything that results in decreased cognitive function can be classified as dementia, and other types of dementia that occur after strokes or through age can compound with patients who suffer Alzheimer's already.

This is increasingly important in understanding the disease, he said, because some types of dementia can be treated. Alzheimer's, unfortunately, cannot.

"The goal in treatment is to maintain the amount of functionality as much as you can," Sadek said. "Medications you would use for certain dementia are different than what you would use for Alzheimer's. The more you know about it, the more you can track the progression of the problem and diagnosis the disease properly."

The causes of Alzheimer's are a mystery, but Sadek said advances made in the past 10 years or so have increased understanding quite a bit. It's hard to guess whether the disease will ever be cured, but research shows signs of being able to slow it down.

Physicians use the age 65 as the cutoff line between early onset of Alzheimer's and late onset. While conclusive evidence is hard to come buy, it's accepted within the medical community that early-onset Alzheimer's has a strong hereditary link. Those who develop Alzheimer's at age 65 or later, however, tend to have sporadic instances of the disease in their family.

Other than that, the only other known risk factor for the disease is age. Sadek said estimates show that 2 percent of the population will have Alzheimer's disease by age 65, 4 percent by age 70, 8 percent by age 75 and so on.

"The technology we have has extended the average life, so it's such a common thing to see in the age group," he said. "If you see it in the mid-50s or earlier, that's very rare."

While it isn't known exactly what causes the disease, it's effect is very well known.

Alzheimer's disease not only kills neurons in the brain but eventually decreases actual brain mass. Imaging of a brain in late stages of the disease shows a stark contrast with a healthy brain, and in some cases, understanding the disease can help families understand a loved one's behavior.

"I had one person see the slides (of an Alzheimer's brain) and say, 'Now I understand,'" Breiner said. "They had been having problems with a loved one, and they said they had closure."