What is Alzheimer's Disease (AD)?
The number of people with Alzheimer's Disease (AD)is rising primarily due to changes in our population. The population of people who are 85 or older is increasing three times faster than the general population. It has been estimated that 9% of post WW2 baby boomers may live to be 100; 0.2% of their grandparents did. AD is a progressive, chronic brain disease. It is the most common form of dementia* and is directly correlated with age. The diagnosis of "definite AD" requires histopathologic evidence from biopsy or autopsy, but the diagnosis of "Probable AD" in primary care, based upon signs and symptoms as well as imaging data, is fairly accurate. AD accounts for between 50 and 65% of dementias. With AD, there is progressive deterioration (over a period of 2 to 20 years) of language, motor skills, perception, and activities of daily living. There can be associated symptoms of depression, insomnia, incontinence, delusions, hallucinations, outbursts, sexual disorders, and weight loss. The diagnosis of "probable AD" requires:
1. The presence of dementia with two or more areas of cognition involved;
The diagnosis of "possible AD" describes patients with either (a) an atypical set of symptoms or (b) typical symptoms but another disorder is present that might produce dementia by itself.
The progression is quite variable; some patients deteriorate rapidly in 1-2 years and others plateau for several years. There are recent findings by G. E. Smith and his colleagues (Neurology, July 10, 2007 issue) that a plateau begins an average of 4 years before AD is diagnosed. "The upregulation in cholinergic activity and presence of neurotrophic factors suggest that the brain stimulates a compensatory mechanism in a region that subserves memory function, particularly early in the disease course.....This pattern of a 'last gasp' of upregulation before mesial temporal pathways ultimately fail might correspond with a circumscribed period of stabilization of memory performance." Since compensatory mechanisms and/or "cognitive reserve" can keep people functioning when brain scans might say they have AD, the best early indicators are longitudinal changes in cognitive abilities.
However the disease progresses, changes in the brain often start many years before a diagnosis is made. There are a wide range of factors associated with the disease (genetics, blood supply to the brain, head injury, exposure to solvents, oxidative stress on cells) but no clear picture yet of why the AD symptoms only occur in a limited set of people in whom these factors are evident.
With Alzheimer's there are abnormal clumps (known as plaques) of protein fragments and cellular debris between the cells. The brain also develops twisted accumulations of protein called neurofibrillary tangles within the cells. The plaques and tangles disrupt normal brain functions, first in the areas responsible for memory and new learning.
What isn't Alzheimer's
Normal aging involves some decline in memory for new information. Multitasking (doing 2 things at once, such as filling out a form while talking on the phone) is particulatly affected. Coming up with a word or a person's name becomes more difficult, but not consistently. Remembering where you parked and other tasks involving spatial memory may deteriorate. The effort necessary to acquire new memories may increase in part because you need to work harder to isolate the memory from other thoughts you are juggling. If event focus/isolation works (e.g. saying outloud "OK, today I am parking straight in front of the Gap on the West side of the mall, Gap, West side, in the row with the light pole, Gap, West, light pole, Gap, West Side, light, Gap store"), that's a good sign that you aren't developing Alzheimer's. The anecdotal evidence we have acquired in the process of testing hundreds of elderly people in primary care offices for MCI suggests that appreciation for the gift of extra years one has already received may reduce the fear that, in turn, interferes with clear and complete attention to the present. Exclusively present-time attention can help in the acquisition of new memories.
With normal aging your vocabulary and other language skills may improve, along with abstract reasoning ability, distant memories and simple attention.
*"Dementia" is actually a group of symptom, not itself a disease or condition. Many diseases and conditions can cause dementia, such as traumatic brain injury, alcoholism, Alzheimer's, stroke and Parkinson's disease. Dementia means impaired cognitive functioning which has progressed to interfere with normal daily life. It means the loss of ability to solve problems, control emotions, make decisions or stay focused in conversations. It can also lead to behavioral problems, such as agitation, due to delusions and hallucinations.