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Dementia life expectancy is a measure of how long an average individual is expected to live after developing dementia. On the average, an individual diagnosed with dementia resulting from Alzheimer's disease will live 4.5 years beyond the diagnosis. While precise figures vary according to the cause of the dementia, age at the time of diagnosis, and other factors, dementia is considered an end-of-life symptom. What this designation means is simply that individuals who have been diagnosed with dementia are reaching the final stage of life. For some individuals, this final stage may last 10 years or longer, but other individuals pass through it in a much shorter period.
The average 4.5-year life expectancy for patients with Alzheimer's disease is further affected by several key factors. An otherwise healthy individual who is diagnosed with the condition prior to age 70 can be expected to live another 10 years, whereas those diagnosed past the age of 90 years usually lose the battle within 4 years of their diagnosis. The individual’s age, overall health and level of care all play crucial parts in his or her life expectancy.
Patients suffering from Alzheimer's disease go through seven stages of dementia. Each of these stages is marked by a further decline in cognitive abilities and memory. During the final stages of dementia, life expectancy for these patients may rapidly diminish as they lose the ability to respond to their environment.
Other diseases and syndromes can be responsible for the early onset of dementia, and life expectancy for these patients varies widely. Three relatively common causes of dementia in adults who are between 45 years and 65 years of age include multiple sclerosis (MS), Huntington's disease and human immunodeficiency virus (HIV).
Patients with dementia brought on by MS can be expected to live an average seven years less than those who do not have dementia. The lifespan of those with Huntington's disease-related dementia is 15 years. Those with HIV who develop dementia have a life expectancy of up to 25 years if they do not succumb to other effects of the virus.
Dementia may also be brought on by the brain being deprived of oxygen and nutrients as a result of strokes or shrinking arteries. This is known as vascular dementia (VaD), and the average life expectancy for these patients is five years or less. Further factors, such as multiple strokes, high blood pressure or other risk factors, may increase the level of dementia suffered by the patient and shorten life expectancy.