How Long Does Dementia Last? Here's What The Research Suggests

Dementia, now formally known as major neurocognitive disorder (MND), is a complex and varied type of progressive brain disease that typically affects the elderly but can also impact younger people in rarer cases. Depending on the type and stage of the condition, dementia can significantly impair a person’s ability to function in daily life. Although MND is often referred to as one condition, it has a variety of subtypes, each of which can progress at a different pace, though most are terminal. Here, we’ll examine a few common types of dementia and explore how they progress and how long they last. 

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What is dementia, or major neurocognitive disorder?

As of 2013, the term “dementia” is no longer diagnostically valid, although it’s still commonly used by the general population. Another term, “Alzheimer’s,” was formerly used to refer to all forms of dementia but is now only used when referring to the Alzheimer’s subtype of major neurocognitive disorder (MND). MND encompasses all dementias that cause significant cognitive decline to the point that a person’s independence is reduced and they find it challenging or impossible to complete some or all of their regular daily activities without assistance. 

Stages, symptoms, and diagnostic criteria for MND

An MND diagnosis requires that the cognitive decline not be better explained by another mental health disorder, such as depression or schizophrenia. MND can be categorized into three severities: mild (early stage), moderate (middle stage), and severe (final stage). Mild MND is characterized by difficulties with instrumental activities of daily living, such as completing housework or handling money. Moderate MND is characterized by difficulties with basic tasks of daily living, such as trouble with dressing or eating. Those with severe MND are completely dependent on caregivers for survival. 

MND subtypes and Alzheimer's disease etiology

MND has replaced dementia as a formal diagnosis, but many of the formerly used terms remain as MND etiology specifiers, or the names of subtypes. Each MND subtype specifies the etiology, or source, of the condition. The MND subtypes listed by the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) include the following: 

• MND due to Alzheimer’s is the most common cause of dementia, accounting for 70–80% of all cases. It’s caused by the accumulation of beta-amyloid plaques and malformed tau proteins within the brain, causing atrophy.  
• Major frontotemporal neurocognitive disorder is responsible for 25% of MND cases in those over age 65. It’s caused by malformed proteins accumulating in the frontal and temporal lobes of the brain. 
• MND with Lewy bodies accounts for about 5% of MND cases. Lewy bodies are clumps of malformed proteins that damage neurons. 
• Major vascular neurocognitive disorder accounts for about 15% of MND cases. It occurs when the brain’s blood supply is interrupted due to stroke, cardiovascular disease, or another cause. 
• MND due to traumatic brain injury occurs when a physical trauma damages the brain. 
• MND due to HIV infection can occur following infection by the HIV virus. 
• MND due to prion disease is when prions (small pieces of misfolded protein) interfere with cellular function. 
• MND due to Parkinson’s disease occurs in as many as 80% of individuals with a diagnosis of Parkinson’s disease. 
• MND due to Huntington’s disease is caused by Huntington’s disease, a genetic mutation that results in damage to neurons in the brain. 
• MND due to another condition is diagnosed when some other medical condition than those listed above causes dementia. 
• MND due to multiple etiologies is diagnosed when multiple conditions contribute to the MND. 
• Unspecified MND is diagnosed when the underlying cause of the MND is unknown. 

The progression of major neurocognitive disorder

“How long does dementia last?” is a common question, especially for those living with MND or caring for someone with MND. The progression of the disease differs based on the type of MND a person is diagnosed with. It’s typically measured in years for all types, but the prognosis and duration can vary based on the underlying causes. 

Impact of early diagnosis on MND progression, memory, and care

A brief overview of the research describing disease progression for common dementia subtypes is below.

MND due to Alzheimer’s and its impact on health

MND due to Alzheimer’s is the most common form of MND and currently the most-researched form of dementia. Because of the significant research base, much more is known about Alzheimer’s than other types of MND. On average, a person has a life expectancy of four to eight years after being diagnosed with Alzheimer’s, but some live as long as 20 years.

MND due to Alzheimer’s is commonly described using a four-stage model of progression:

• Preclinical Alzheimer’s disease. Preclinical Alzheimer’s is when cognitive function begins to decline, but the decline does not yet adversely impact most activities of daily living. It’s not always possible to diagnose Alzheimer’s in this stage, with many patients being diagnosed with a mild cognitive impairment (MCI) instead. If a person is diagnosed with an MCI, it will not always progress to Alzheimer’s; in fact, fewer than 15% of people diagnosed with an MCI eventually develop MND. 
• Mild Alzheimer’s disease. In this stage, a person can still function independently, but symptoms are becoming noticeable. Common symptoms include memory lapses, difficulty completing some tasks, losing objects, and trouble planning or organizing. 
• Moderate Alzheimer’s disease. This is the longest stage, typically lasting for several years. The person may become more confused, irritable, and frustrated with their circumstances. They will likely struggle to complete routine tasks without assistance. Memory lapses become more severe, and the person may struggle to remember significant events or details from their personal history. 
• Severe Alzheimer’s disease. At this stage, most individuals are entirely dependent on full-time care for survival. They may know only a few words and struggle to communicate, typically lose their physical abilities, and may not be able to recall recent experiences. Hospice care or residential care is common at this stage. 

Frontotemporal MND

Frontotemporal MND, formerly called frontotemporal dementia (FTD), is diagnosed when evidence of progressive degradation of the frontal and temporal lobes of the brain is present. The frontal lobe is responsible for executive function and conscious control. Damage to the area causes changes in personality, behavior, and judgment. Sometimes, a person’s ability to control their movement will also be affected. The temporal lobe is heavily involved in communication, so damage to that area may result in a progressive deterioration of a person’s ability to speak, read, and write. 

Major frontotemporal neurocognitive disorder often affects those who are relatively young—usually between 45 and 64 years old. Those with frontotemporal MND typically live four to six years after being diagnosed, but early diagnosis and consistent support may affect life expectancy substantially. 

How long does dementia last in MND with Lewy bodies?

MND with Lewy bodies, formerly known as Lewy body dementia, can cause significant problems with cognition, movement, sleep, and behavior. Unlike Alzheimer’s, memory impairment is not typically present in its early stages. Instead, a person might experience trouble paying attention, staying organized, or using logic. Sleep is also commonly affected, and sleep deprivation may contribute to the progression of MND with Lewy bodies. Changes in mood, such as depression, anxiety, and agitation, are also common. 

On average, determining how long dementia lasts in MND with Lewy bodies can be challenging, as progression varies significantly from person to person. Late-stage dementia due to MND with Lewy bodies is typically characterized by weight loss, social isolation, and severe cognitive impairment. On average, it takes a person five to eight years to progress to the final stages following diagnosis, but some people survive up to 20 years. 

Other types of MND

Other types of MND are typically caused by underlying medical conditions or a traumatic brain injury, which can substantially affect how long a person may live after being diagnosed. For example, those diagnosed with major vascular neurocognitive disorder, which occurs following an interruption of blood flow to the brain, typically live five years on average after being diagnosed. This person’s expected longevity would be lower than with other MND types, like Alzheimer’s, but this is due to the likelihood of additional vascular problems like stroke and not the dementia itself.

Seeking emotional support

Coming to terms with your own dementia diagnosis or the diagnosis of a loved one can be difficult and stressful. One way to help manage this kind of stress is to contact a therapist or counselor for support. Many people are now choosing to do this virtually, via online therapy. Online therapy allows you to attend counseling sessions from home, so there’s no need to travel to a physical office, and it’s often more affordable than in-person options as well.

Effectiveness of online therapy compared to in-person therapy

Online therapy has been and continues to be extensively researched. Online therapists also use the same evidence-based practices as traditional therapists. In the early days of online therapy, some were concerned that methods that were effective in person would not be as beneficial when administered online. However, a growing body of research suggests that, in most cases, online therapy is just as effective as in-person therapy.