Dementia is a general term for a decline in mental ability severe enough to interfere with daily life. Dementia is not a single disease but a term that describes symptoms associated with a decline in memory or other thinking skills that reduce a person’s ability to perform everyday activities. Alzheimer’s disease is the most common cause of a progressive dementia in older adults, accounting for 60 to 80 percent of cases. Vascular dementia, which occurs after a stroke, is the second most common dementia type. There are many other conditions that can cause dementia or dementia-like symptoms.
The progression of dementia depends greatly on the underlying cause. On average, a person with Alzheimer’s disease lives 4 to 8 years after diagnosis but can live as long as 20 years, depending on other factors. In vascular dementia, life expectancy also varies depending on the severity of the blood vessel damage in the brain. While some forms of dementia worsen quickly over several years, others can progress very gradually over more than a decade.
What affects life expectancy with dementia?
Many factors affect how long someone will live after a dementia diagnosis. The most important is the type of dementia since some forms progress faster than others. Additionally, the following factors play a role:
- Age at diagnosis – Younger people typically live longer with dementia than those diagnosed at older ages.
- Coexisting health issues – Other chronic conditions like diabetes or heart disease can shorten life expectancy.
- Severity at diagnosis – People with more advanced dementia tend to have shorter survival times.
- Access to care – Ongoing medical care and social support can prolong survival.
- Other neurological problems – Dementia complicated by seizures, Parkinson’s disease, etc. may progress faster.
- Genetics – Some genes might be associated with longer survival times.
While these factors contribute to an individual’s prognosis, the average survival times provide general expectations based on studies of large groups of people with various types of dementia.
Average life expectancy by type of dementia
Here are the approximate life expectancies after diagnosis for some of the most common types of dementia:
Alzheimer’s disease
- Average life expectancy: 4 to 8 years
- Range: 2 to 20 years
Alzheimer’s disease is characterized by progressive mental decline and accounts for 60 to 80 percent of dementia cases. On average, people live 4 to 8 years after an Alzheimer’s diagnosis but can live up to 20 years with proper care.
Vascular dementia
- Average life expectancy: 3 to 5 years
- Range: 1 to 10 years
Vascular dementia is cognitive impairment caused by damage to the blood vessels in the brain. It is the second most common type of dementia after Alzheimer’s. Life expectancy depends on the extent of vascular damage.
Lewy body dementia
- Average life expectancy: 5 to 8 years
- Range: 2 to 20 years
Lewy body dementia involves abnormal protein deposits (Lewy bodies) in areas of the brain that control thinking, memory, and movement. Survival time is similar to Alzheimer’s but has a wider variation.
Frontotemporal dementia
- Average life expectancy: 6 to 8 years
- Range: 2 to 20 years
In frontotemporal dementia, damage to the frontal and temporal lobes of the brain impacts personality, behavior, and language. Life expectancy is slightly longer than Alzheimer’s on average.
Mixed dementia
- Average life expectancy: 4 to 6 years
- Range: 1 to 14 years
Mixed dementia refers to a diagnosis of two or more types of dementia at the same time, most commonly Alzheimer’s and vascular dementia. Survival time is generally shorter than for Alzheimer’s alone.
Life expectancy based on age at diagnosis
Age at the time of diagnosis is another important factor in determining life expectancy with dementia. Younger people typically live longer with dementia than those diagnosed at more advanced ages. Here are some estimates grouped by age:
| Age at Diagnosis | Average Survival Time |
|---|---|
| 65 years | 8 to 10 years |
| 70 years | 6 to 8 years |
| 75 years | 4 to 6 years |
| 80 years | 3 to 4 years |
| 85 years or older | 2 to 3 years |
As shown, younger people at the time of diagnosis tend to live longer with dementia compared to those diagnosed at more advanced ages. However, there is a great deal of variability between individuals based on the specific type of dementia and other health factors.
Life expectancy based on stage at diagnosis
The stage or severity of dementia at the time of diagnosis also correlates with life expectancy. People diagnosed at earlier stages generally live longer than those with advanced dementia at the time of diagnosis. Here are typical survival times based on the stage:
| Stage at Diagnosis | Average Survival Time |
|---|---|
| Mild dementia | 6 to 8 years |
| Moderate dementia | 4 to 5 years |
| Severe dementia | 1 to 3 years |
Mild dementia typically refers to noticeable cognitive problems but preservation of independent function. Moderate dementia involves worsening symptoms and need for assistance with daily activities. Severe dementia indicates major memory deficits, difficulty communicating, and dependence on others for care.
What happens in end-stage dementia?
End-stage or late-stage dementia is the most advanced stage and occurs when dementia symptoms become extremely severe. Hallmarks of end-stage dementia include:
- Inability to communicate coherently
- Minimal verbal communication
- Loss of ability to walk independently
- Incontinence
- Inability to care for oneself
- Difficulty swallowing
- Weight loss
- Muscle rigidity or spasticity
- Vulnerability to infections
In end-stage dementia, individuals essentially lose their ability to engage meaningfully with their environment or care for themselves. Round-the-clock nursing care is usually required. Survival at this stage is difficult to predict but typically ranges from several weeks to about 1-2 years. The primary goal of care is preserving comfort and quality of life.
What is the life expectancy after dementia diagnosis?
In summary, average life expectancy after a dementia diagnosis depends mainly on the type and stage of dementia. Younger age at diagnosis and access to quality care are two factors that can prolong survival. However, there is significant variation based on individual circumstances.
People with Alzheimer’s disease live an average of 4 to 8 years after diagnosis but some may survive up to 20 years. Vascular dementia life expectancy is 3 to 5 years on average. With Lewy body dementia, survival averages 5 to 8 years. And frontotemporal dementia life expectancy is slightly longer at 6 to 8 years. Mixed dementia typically shortens survival compared to Alzheimer’s alone.
Those diagnosed at earlier stages of dementia generally live longer as well. Mild dementia life expectancy is about 6 to 8 years, while moderate dementia survival is 4 to 5 years. People with severe dementia at diagnosis live 1 to 3 years on average. In end-stage dementia, life expectancy ranges from several weeks to 1-2 years.
While these estimates provide general guidance, every person’s experience with dementia is unique. With quality care and support, life expectancy can be improved. Researchers continue working to develop better treatments to slow the progression of dementia and extend survival times.
Conclusion
On average, Alzheimer’s shortens life expectancy by about 4 to 8 years after diagnosis, while vascular dementia shortens life expectancy by about 3 to 5 years. However, there is significant variation based on the type of dementia, age at diagnosis, severity of symptoms, and other health factors. Improving diagnosis and access to care and support can help prolong meaningful life. Researchers continue efforts to develop more effective treatments to slow dementia progression and prolong survival.