By David Park
Dementia is characterized by the development of multiple cognitive deficits, including memory (deficits in learning new information or in recalling previously learned information) and at least one of the following: language (word retrieval difficulties, defects in understanding complex commands, loss of semantic knowledge), perception (problems in the identification of objects or in the recognition of familiar places), praxis (impairment in the ability to carry out complex movements), and executive functions (inability to plan and organize behavior). Calculation ability defects and conceptual difficulties are also commonly found. These deficits are usually progressive but in some cases are static. Dementia also involves personality and emotional changes. Lack of awareness that the patient has the disease is often found . Psychiatric symptoms such as delusional ideas and hallucinations also might develop. As the disease progresses, these deficits impair the social and occupational functioning of the individual.
Dementia increases sharply with age. Most dementias are found in people older than 65. The prevalence for all dementias is over 2% by age 65 and over 30% for those 85 or older. Fifty percent to 70% of the cases of dementia correspond to an Alzheimer-type dementia; approximately 35% have pure Alzheimer's disease (AD); the remaining have AD associated with vascular disease or Lewy body pathology. The second most common type of dementia is vascular dementia, making up 10% to 30% of the dementia cases. The prevalence of frontotemporal dementia has been estimated at 5%. The prevalence of other types of dementia is less clear.
Alzheimer's disease is characterized by the presence of progressive cognitive decline in at least two cognitive domains. The decline in memory with deficits in episodic memory that progresses to amnesia is characteristic of AD. Word-finding difficulties that evolve into an anomia (poor naming) and impaired...