Dementia and Alzheimer's disease classification

Dementia

Alzheimer's disease is a type of dementia, of which there are many types. Dementia is a term that describes a number of conditions that lead to a loss of intellectual capacities but initially occurring with clear consciousness. The area most often first affected is memory; however, with some types of dementia this may not be the case. The DSM-IV-TR diagnostic criteria for dementia consist of memory loss and the loss of one other cognitive domain. The disorder must result in significant impairment or distress either social, occupational or some other area of the person's functioning and must also constitute a marked change from the person's prior functioning (American Psychiatric Association [APA], 2000).

Alzheimer's Disease (AD)

Alzheimer's disease (AD) accounts for majority of dementia cases (50-60%) followed by vascular dementia (between 15-30%). Other common forms of dementia include Lewy body dementia and dementia associated with Parkinson's disease, but there are many different causes of dementia (Sadock & Sadock, 2007). AD is named after its discoverer, Alois Alzheimer, who observed the signs of AD in a 51-year-old female patient in 1901. The patient died in 1906 Alzheimer was able to examine her brain and determine the pathology associated with the disease, which he described in 1907 (Ropper & Samuels, 2009).

Facts about AD

AD is misunderstood by the public and the media often reports on many preliminary research findings, some of which are speculative and not reproduced) that fosters many misconceptions. Here are some facts about AD:

First, AD is a brain disease. There is quite a bit of speculation concerning the etiology of AD; however, there has not been a definitively identified cause for AD. There are a number of risk factors that contribute to the probability of developing the disease, but these are not direct causes but are contributory factors that increase the possibility that a person can develop a condition. The biggest risk factor for developing AD is age; however, this does not mean that AD is the result of getting older. A family history of AD is another risk factor. There have some genetic factors associated with AD; the most well-known is the presence of the APOE4 allele. Being positive for this gene increases the risk of developing Alzheimer's disease. To date there is no direct genetic link to AD except in perhaps persons with Down syndrome, who develop Alzheimer's disease at a rate of almost 100% after the age of 40 and a familial from of AD that occurs well before the age of 60. Other risk factors include a history of head injury, hypertension, vascular disease, or diabetes. Females are statistically more likely to develop Alzheimer's disease, but they also live longer than males so this may in part reflect the age effect (APA, 2000; Launer et al., 1999).

Second, even with improved diagnostic techniques a diagnosis of AD is not 100% certain unless there has been a brain biopsy or autopsy. The pathology associated with AD can only be definitively identified by means of a histological examination of the brain. All of the laboratory tests and brain scans can rule out other conditions that mimic AD and help support the probable diagnosis of AD (Ropper & Samuels, 2009). The brain pathology of AD consists of (Miller & Boeve, 2009):

1. Massive Neuronal Loss. The brains of AD patients are characterized by a massive loss of neurons and look smaller and more shrived compared to the brains of their age-matched normal peers.

2. Senile Plaques. These are deposits of beta amyloid in the brain which are clumps of insoluble fibrous protein that are associated with the neuronal loss. They are believed to produce a neurotoxic effect and are akin to functionless brain scar tissue.

3. Neurofibrillary Tangles. The neurofilaments of a neuron are the skeletal structures of the cell and serve as the transport system for components within the neuron. When these become malformed the cells cannot function properly nor send messages to other neurons. Tangles also lead to cell death.

Third, there is no cure for AD. AD is progressive and is 100% fatal (although many elderly patients may die from other complications). There are many conditions that mimic dementia and are reversible. The average expected lifespan for a person diagnosed with early AD is about seven to eight years, but the course can last anywhere from one to twenty years (Molsa, Marttila, & Rinne, 1995; Ropper & Samuels, 2009).

Fourth, there is no way to predict for certain if a person will develop AD. Recently, there have been a number of studies using PET scanning or other brain scanning techniques that demonstrate promise in identifying individuals at risk to develop AD, but all these at risk individuals will not develop dementia (Ropper & Samuels, 2009).

Fifth, AD appears to have several subtypes which do not have the same progression in every individual (Ropper & Samuels, 2009).

Treatment for AD

There is no cure for AD but there have been medications developed that are hypothesized to slow the course of early AD and one class of medications hypothesized to accomplish this in the later stages. Medications are (Miller & Boeve, 2009; Sadock & Sadock, 2007):