Swank Center for Memory Care and Geriatric Consultation, ChristianaCare
Learn about the many factors that affect average life expectancy after a diagnosis of Alzheimer’s disease.
Genevieve* asked if she could speak privately with me after her mother’s evaluation session and diagnosis of Alzheimer’s disease. “I didn’t want to ask this in front of her,” she said, “but my brother and I want to know…how much time does she have left?” Life expectancy after a diagnosis of Alzheimer’s disease, while uncomfortable to discuss, can be important information for patients and families to have. I’ll describe what we know about this topic, and some of the factors that affect survival with and without dementia. Please bear in mind that this information is based on statistical averages, and there can be individual variations in the disease and a person's resilience to it.
*The name and details were changed to protect privacy.
The most honest answer to Genevieve’s question may be, “It depends.” After a diagnosis of Alzheimer’s disease or another dementia, people can live for months to years, depending on individual circumstances. It’s been shown that factors like age, race, genetics, health background, socioeconomic status, and education influence the life expectancy of large numbers of people with Alzheimer’s. However, every individual’s disease is different, and may not follow the average course.
Dementia is one of the top causes of death in the United States, and the events leading to death in a person with dementia – such as complications related to an infection after aspiration, or falling – are not always directly linked to the disease. In order to provide a more useful answer, I want to write about life expectancy in general and then I’ll list some of the factors that help us think about survival. Again, while these may influence life expectancy with Alzheimer's in general, individuals sometimes depart from statistics and have a different disease course.
For anyone with dementia, there is a period of survival with the disease, and this can be a challenging and complicated time for caregivers, a time during which family members need to work together, plan for the future, and cope with an increasingly difficult set of circumstances.
“Life expectancy at birth” is the standard statistic that we use, and this is defined as the average number of expected years from birth to death for members of a population. Many factors affect the number of years we are expected to live, including the year of birth, sex, race, and income level.
As with life expectancy in general, many factors affect the expected length of survival after a diagnosis of dementia. If we include everyone of all ages, average life expectancy is decreased by almost nine years by dementia, but this number can be further refined based on individual characteristics. For example, an individual’s sex is a factor affecting survival after dementia, just as it affects life expectancy in general. At all ages, expected survival after a dementia diagnosis is about 1.5 years longer for women than for men. Scientists are researching the biological basis for this, and it may also be explained in part by differences in social norms (for example, women may be more likely to seek medical advice that prolongs their lives).
Earlier detection may mean an extended period of survival with the disease. Although currently there are no approved disease-modifying therapies capable of delaying or curing AD, there are a growing number of lifestyle recommendations and new personalized medical approaches which involve assessing the unique aspects of an individual’s Alzheimer’s disease and overall health, and developing personalized therapies. Interventions might include such things as changes to diet, exercise, and sleep habits; cognitive training; and increased social engagement. While primarily aimed at improving quality of life with Alzheimer’s disease, these lifestyle changes also may benefit life expectancy by helping people better manage their AD and overall health.
The age at diagnosis, too, is important because an older individual may already be frail and vulnerable to additional life-shortening accidents, diseases, or infections. Life expectancy after a diagnosis of dementia decreases with increasing age; for example, an average person diagnosed with Alzheimer’s disease between ages 70 and 79 can expect to survive seven more years, while diagnosis after age 90 is associated with an expected survival of only 2.8 additional years.
The presence of comorbid diseases (one or more additional medical conditions), too, may accompany aging and shorten life expectancy.
Although Alzheimer’s disease is our focus here, a discussion of survival should consider other dementias as well. Survival after a diagnosis of Lewy body dementia is significantly shorter than survival after a diagnosis of Alzheimer’s disease. Survival lengths after a diagnosis of vascular dementia or frontotemporal dementia are intermediate. Compared to dementia, a diagnosis of mild cognitive impairment is associated with a smaller reduction in life expectancy, and in many cases does not lead to Alzheimer’s disease and dementia.
Life expectancy after a diagnosis of Alzheimer’s disease varies from person to person. In the case of Genevieve’s mother, a white woman of age 75 at the time of her diagnosis, I estimated her expected survival to be around 6.7 years. This ballpark figure might prove correct or not since it is an estimate based on a population rather than a certainty for this individual. Having a general idea of expected survival assisted Genevieve’s family in facing the most probable future, planning, and valuing the preciousness of each remaining day.
James Ellison, MD received his medical degree from UCSF in 1978 and trained in psychiatry at the Massachusetts General Hospital (1979-1982).
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