Dementia

There are close to 100 different diseases associated with the clinical symptoms of dementia. While the causes of some are known (e.g., traumatic injury, stroke, brain tumors, infection, vitamin deficiencies, and nervous system toxicity from substances such as alcohol, cocaine, opiates, marijuana, inhalants, and heavy metals), the causes of many dementia producing diseases are still being sought. Ongoing research continues to advance our understanding of these disorders. This is particularly true of the most common dementia producing disorder, Alzheimer's disease, which accounts for approximately 50 to 70 percent of all cases of dementia in old age (or about 3–5% of the U.S. population over the age of 65) (Rabins et al. 1999). First described in 1907, Alzheimer's disease is a degenerative brain disorder characterized by amyloid plaques and neurofibrillary tangles in the brain. Early stages of Alzheimer's disease include memory problems, followed by impairments in language and the ability to do daily tasks. In later stages, impairments in memory, communication, and physical ability become quite severe. While some progress has been made in slowing memory losses in the early stages of Alzheimer's disease, treatments to prevent or cure the disease are not yet available (National Institute on Aging and National Institute on Health 1999).

Another leading cause of dementia, cerebrovascular disease, is associated with vascular dementia (also referred to as multi-infarct dementia) (Ringholz 2000). Sometimes mistaken for Alzheimer's disease, vascular dementia may appear to have a more sudden or step-wise onset than Alzheimer's disease. Also, in contrast to Alzheimer's disease and most of the other dementia-producing diseases discussed here, the progression of vascular dementia may be slowed or stopped by addressing the underlying cause of the damage (e.g., strokes or other brain damage due to cerebrovascular disease) (Rabins et al. 1999; Ringholz 2000).

Also often mistaken for Alzheimer's disease, Lewy body disease is receiving increased attention as a significant cause of dementia in later life (Brown 1999). First described as a distinct disorder in the mid-1990s, Lewy body disease is an irreversible degenerative disorder associated with protein deposits in the brain called Lewy bodies. Symptoms vary depending on where the deposits are located, but typically include problems with motor coordination similar to those seen in Parkinson's disease (McKeith and Burn 2000). In early stages, forgetfulness, walking instability, and depression may be seen. In the middle stages, cognitive impairments seem to fluctuate but become more frequent at night. The final stage is characterized by rapid cognitive decline, delusions, and hallucinations.

In addition to the most widely known disorders described above, there are a number of less common dementia producing diseases. For example, frontotemporal degeneration is a group of dementia-producing disorders in which there is degeneration in the frontal and temporal lobes of the brain. Frontotemporal degeneration has been known by a number of different names, including frontal lobe dementia and Pick's disease. Frontotemporal degeneration usually begins with changes in personality and behaviors such as the ability to follow social rules and think abstractly. Prevalence of frontotemporal dementia is thought to be fairly low (up to 3% of all patients with dementia). Since it is associated with an earlier onset (around age fifty-four), it may account for closer to 10 percent of those who die with dementia before age seventy (Rabins et al. 1999).

Huntington's disease (formerly known as Huntington's Chorea), is a rare, inherited degenerative disorder which can produce slurred speech and problems with physical movement in addition to the progressive symptoms of dementia. When the gene for Huntington's disease is inherited, there is almost certain that the disease will occur. Onset of the disease is variable, ranging from age two to age seventy, although it is mostly a disease of adulthood (average onset is in the late thirties to forties). Due to the physical disturbances, early stages of Huntington's disease may be mistaken for alcoholism (Rabins et al. 1999; Siemers 2001).

Prion dementias represent an even more rare group of diseases. Known as spongiform encephalopathy because of the characteristic degeneration of the neurons and a spongy appearance of the brain's gray matter, prion dementia was first described in 1921. Although Bovine Spongiform Encephalopathy (BSE), also known as "mad cow disease," is the most widely known form of the disease, two additional forms of spongiform encephalopathy (Creutzfeld-Jakob disease and Gerstman-Straussler-Scheinker syndrome) are associated with dementia in humans. With spongiform encephalopathy, the progression of symptoms is rapid and change can occur over weeks. Prion dementia is very rare—literally one in a million (Nguyen and Rickman 1997).

In addition to the disorders described above, several forms of dementia have been associated with outside agents. Some involve exposure to toxins such as alcohol or heavy metals (e.g., lead, arsenic, or mercury). Others are associated with infectious agents such as syphilis and human immunodeficiency virus (HIV). The growing body of research on HIV/AIDS (acquired immunodeficiency syndrome) suggests that AIDS dementia complex (also known as HIV-associated dementia) may affect up to 60 percent of patients with AIDS before their death (Brew 1999; Rabins et. al 1999).