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What is the life expectancy of a person with dementia at 78?

According to a 2025 systematic review published in *The BMJ*, dementia reduces life expectancy by an average of 3-4 years for those diagnosed around age 80. For a person with dementia diagnosed at age 78, the life expectancy varies significantly based on the specific type of dementia, overall health, and gender. While average estimates exist, many individual factors can influence a person's remaining years after a diagnosis.