Life Expectancy Calculator for Alzheimer’s Disease & Dementia

Last Updated: May 25, 2021


The Short Answer to a Big Question

On this page we will discuss the development of an Alzheimer’s / dementia Life Expectancy Calculator, but let’s first address the question most people ask after receiving the diagnosis of an incurable disease: How long do I have left to live? With dementia, the answer differs depending on the type. By far the most common form of dementia is Alzheimer’s disease, and the average life expectancy after diagnosis is 10 years. Other dementias have different life expectancies. Someone with vascular dementia lives for about five years after diagnosis. Someone who has dementia with Lewy bodies will typically live for six to twelve more years.

Average life expectancies for the most common types of dementia are as follows:

Dementia type Average life expectancy following diagnosis
Alzheimer’s 8 – 12 years
Vascular 5 years
Lewy body 6 – 12 years
Frontotemporal 8 years
Huntington’s 10 – 20 years

However, keep in mind that everyone with dementia experiences impacts and symptoms differently. People have lived more than 25 years after being diagnosed with Alzheimer’s disease. Factors including underlying health, the severity of early symptoms, and even gender come into play.

But how can a person know how long they have to live when they’re diagnosed with dementia? Is there an Alzheimer’s Life Expectancy Calculator to get as close to a definitive answer as possible? Can artificial intelligence help? And why would they want to know?

 Cut to the Chase: Use our experimental Alzheimer’s Life Expectancy Calculator now.


Why Knowing Life Expectancy is Useful

Knowing what to expect, including life expectancy (even if this is very sad information) helps with planning. Someone predicted to survive for five or six years, as opposed to two years, will want to make more extensive plans, including getting an estate in order, activity planning, and budget. Knowing how quickly the disease is expected to progress symptomatically can impact care decisions. If the disease is predicted to come on very quickly, for example, then skipping traditional assisted living and looking into memory care or a nursing home might be the best option.

Knowing when full-time care becomes a requirement, either at-home or in a memory care residence, is especially useful given the high cost of care. It is estimated that 50% of nursing home residents have some level of dementia and over 60% of nursing home residents’ care is paid for by Medicaid. Medicaid eligibility is complicated, and families can spend up to 5 years waiting for a loved one with dementia to become Medicaid-eligible. Therefore, knowing how soon care is required can make a huge financial difference.

 Contribute anonymously to our dementia life expectancy database.  Start here.


Evidence that Life Expectancy Calculators for Dementia Actually Work

It turns out that the length of time a person has before needing full-time care, before moving into a care community, and before dying can all be predicted somewhat accurately. This information, though not definitive, can help families get a general understanding of how to plan for the future and what to expect as the disease progresses.

In a study conducted at the department of neurology in Columbia University, groups of people with mild Alzheimer’s were followed for 10 years and assessed semiannually. Data from these assessments were plugged into a complicated algorithm. The people studied were tested for the following:

– Mental status (mini-mental status exam) score
– Cognition (thinking ability) and function (physical ability)
– Motor skills
– Psychology and behavior
– Basic demographic information

The model worked. 506 total people were used for this experiment, all with mild dementia at the start, and the predictions were about 95% accurate. Researchers could tell when a person with dementia would need full-time care, when it would be necessary to move into an institution like assisted living with memory care or a nursing home, and ultimately when a person would die.
For example, two 68-year-olds with Alzheimer’s disease recorded mini-mental status exam scores that were in the high 30s on their initial visit, but one patient needed a full-time caregiver and had delusion symptoms while the other was more independent. When these and other data were plugged into the model, different times of death were predicted. The first patient lived less than three years, while the more independent person lived more than 10 years. These outcomes were predicted by researchers in the study and came to be true.

Other experiments have yielded similar results. A University of Kentucky study analyzed the records of more than 1,200 people with dementia and found that it was possible to accurately predict their life expectancy. Researchers looked at many variables including family history and medical problems like high blood pressure and heart disease, and ultimately realized it came down to three things:

– age when the first symptoms appeared
– gender
– how impaired someone was when diagnosis was first made

The models were similar. A woman in her 80s with moderate dementia was expected to live about five years after diagnosis, while a man in his 60s with mild dementia lived around seven more years, according to the study. Importantly, these are all theoretical, and researchers who found their models to be highly successful still advise that it is impossible to specifically pinpoint when a person will die. In other words: There is no way of getting an exact number, just a rough idea.


Variables Impacting Life Expectancy Calculations

● Gender. Men don’t live as long with Alzheimer’s as women. A study of more than 500 people diagnosed with Alzheimer’s disease between 1987 and 1996 found that women with Alzheimer’s live, on average, 20% longer than men.
● Age. Someone diagnosed at 65 lives an average of about eight years, while someone over 90 who gets a diagnosis typically lives about three-and-a-half more years.
● Strength of Symptoms at Diagnosis. If someone is showing especially severe dementia-related problems at the time of diagnosis, this usually leads to an earlier death. Someone who wanders, is prone to falling, and experiences urinary incontinence (loss of bladder control), will typically not live as long. A lower mini-mental state examination (MMSE) score at the time of diagnosis will also not live as long. (MMSE is a 30-question exam that tests thinking ability.)
● Other Health Problems. A person with a history of heart problems or asthma or diabetes, for example, will not live as long as someone without those underlying issues.


Life Expectancy by Stage of the Disease

The average number of years a person lives with Alzheimer’s disease is about 10. Keep in mind, however, that there’s a gap between when symptoms begin and when a diagnosis is actually sought. The first symptoms of Alzheimer’s disease—forgetting names, misplacing items, difficulty concentrating at work or performing simple tasks—arrive an average of almost three years before the diagnosis is made.

The scale most commonly used by health professionals for the stages of dementia is the Global Deterioration Scale (GDS), also called the Reisberg Scale. The table below shows a patient’s average life expectancy by the stage of dementia. These are averages based on studies of large numbers of Alzheimer’s patients.

Life Expectancy By Stage of Alzheimer’s / Dementia (according to the Reisberg / GDS Scale)
Stage Expected Duration of Stage Estimated Life Expectancy (Years Remaining)
Stage 1: No Cognitive Decline N/A N/A
Stage 2: Very Mild Cognitive Decline Unknown More than 10 years
Stage 3: Mild Cognitive Decline Between 2 years and 7 years 10 years
Stage 4: Moderate Cognitive Decline 2 years Between 8 and 3 years
Stage 5: Moderately Severe Cognitive Decline 1.5 years Between 6.5 and 1.5 years
Stage 6: Severe Cognitive Decline 2.5 years 4 years or less
Stage 7: Very Severe Cognitive Decline 1.5 to 2.5 years 2.5 years or less

People with early onset or young-onset dementia live for about the same number of years after diagnosis as those with more common forms of dementia. About 5% of cases of Alzheimer’s disease are young-onset, meaning symptoms develop between the ages of 30 and 60. For a long time, it was believed that young-onset Alzheimer’s disease progressed more rapidly than the typical Alzheimer’s disease seen in the brains of people over 65, and therefore caused death faster. Newer studies, however, refute this. In fact, there is evidence that younger age at the time of receiving a dementia diagnosis (of any type) is associated with longer survival with the disease because of factors including overall better health. That said, someone with young-onset dementia has an overall shorter life expectancy than someone diagnosed after 65, because of course they develop symptoms at a much younger age. People with young-onset dementia live an average of 10 years with the disease.


Do Treatments Add Time to Life Expectancy?

Experts simply don’t know whether treatments help a person live longer with Alzheimer’s disease. AD and other similar dementias progress no matter what. Treatments like medications and therapies have been conclusively shown to help manage symptoms, meaning they make it easier to live with the disease, but they do not reverse symptoms. The memory of a person with dementia who takes medications like cholinesterase inhibitors, for example, will be slightly better than the memory of someone who is not on medication. Quality of life therefore improves with treatment. This means better years with dementia, but probably not more years.