Alzheimer’s disease is a concept in evolution; it is considered by most to be a degenerative brain disease that was first described in 1906 and is the most common cause of dementia. Over the past 100 years, we have learned that many biological and clinical phenomena are included under the rubric of Alzheimer’s disease and that perhaps the term can best be considered a two-word eponym that reveals as much about our ignorance as about our knowledge.
Alzheimer’s disease is characterized clinically by the insidious onset of cognitive difficulties, most commonly in memory and attention, that subsequently progress to involve language, perception, praxis, and (frequently) behavioral and psychological symptoms. Neuropathologically, the condition is characterized by progressive loss of neurons in association with neurofibrillary tangles and senile plaques. The cause of Alzheimer’s disease is unknown, although a variety of genetic mutations can cause early onset of Alzheimer’s disease and genetic susceptibility factors that modify late-onset disease have been identified. Much attention has focused on early recognition of Alzheimer’s disease, and a variety of labels, such as the controversial concept of mild cognitive impairment (MCI), have been used to label people who have mild intellectual difficulty. However, these terms are used primarily in research and should not be used clinically.
Alzheimer’s disease is said to be the most common dementia worldwide, followed by vascular dementia and a variety of other neurodegenerative diseases such as Lewy body dementia and frontal lobe dementia. However, precise figures for incidence and prevalence are difficult to determine globally because of the differences in diagnostic criteria and assessment methodologies used in different countries.
