"I'm awfully forgetful - could I have Alzheimer's doc?" That's a question I've been hearing a lot lately. Some forgetfulness is normal for most of us as we age. Many of us carry the fear of developing Alzheimer's dementia as we get older. We are more likely to encounter someone with Alzheimer's as the proportion of elderly in our society increases. This segment of our population is also reaching much older ages where the disease is more likely to occur.

The word dementia stems from the Latin de- "apart or away" and mentis "mind." It is characterized by a progressive decline in cognitive and behavioral function due to damage or disease in the brain beyond what is expected in normal aging. Alzheimer's disease or AD is the most common cause of dementia.

Approximately 5.2 million people in the U.S. suffer from clinically significant AD. There are many more who have mild disease (mild cognitive impairment) that remain functional. Most cases of AD are sporadic, while about 7 percent of cases are genetic in origin.

About 14 percent of individuals over age 65 and 40 percent of those over 80 have AD. It is estimated that by the year 2030 there will be 7.7 million Americans over age 65 with AD. The cost of caring for Americans with AD in 2005 was a staggering $84 billion.

Alzheimer's is a type of dementia resulting from specific anatomic changes in the brain. The two hallmark findings seen under the microscope are neurofibrillary tangles (NFT) and senile plaques (SP). They were first described by Alois Alzheimer in 1907.

Although NFTs and SPs are found in AD, they can also be seen in other neurodegenerative diseases. These lesions must be found in sufficient numbers and in a specific anatomic pattern in the brain to make the diagnosis of AD. There are also other lesions found in AD that I don't have space to describe.

Normally, nerve cells are very ordered, following specific paths that allow them to communicate with neighboring cells. This allows us to think and act clearly. The appearance of normal nerve cells would be analogous to straight strands of hair. The nerve cells in AD look like badly tangled hair. The senile plaques that form are like mixing bubble gum in these tangles of hair. The resulting mess of nerve cells drastically reduces the ability of the cells to function properly.

The diagnosis of AD is very complex and there are numerous criteria that have to be met that are too complex to detail here. Diagnosis usually requires the involvement of a team of medical experts. A doctor usually starts by doing a history and physical exam along with some basic blood work to look for other conditions that can mimic AD. These may include, among others, infections, vitamin deficiencies, and thyroid disease.

The next level of testing usually involves brain imaging tests such as CT scans or MRIs. A brain wave test or EEG may also be done, and genetic testing may be done if there is a family history of AD. Specialized neuropsychological testing may be done to identify exactly which parts of the brain are affected.

The earliest finding in AD is that of slowly progressive memory loss. Forgetfulness is what causes most people to worry they may be developing AD. Occasionally forgetting things like where you placed your keys or why you came into a room is not necessarily a cause for concern. It's more worrisome when memory problems start to interfere with day-to-day functioning. There is an excellent list of warning signs found at www.alz.org under the tab "Know the 10 Signs." This site also contains a wealth of information about the disease.

The underlying cause of AD has been very elusive. Recent research is shedding light on the biochemical pathways leading to AD. This is providing scientists with targets for drug therapy to prevent the disease instead of just trying to slow the progression with currently available medications. Hopefully AD will be a disease of the past in the not-to-distant future.