How Senility and Dementia Differ

Inaccurate definitions can cause confusion and misperceptions

The most basic definition of senile from Merriam-Webster is "relating to, exhibiting, or characteristic of, old age." Thus, the pure use of the word senile simply refers to advanced age.

However, the use of the word senile is more commonly, but somewhat incorrectly, associated with a decline in mental abilities, such as memory loss or confusion as people age. Take, for example, this sentence: "Their senile grandmother would never remember their visits, but they knew they brightened her day."

Two doctors studying images of the brain
Monty Rakusen Cultura / Getty Images

Senile is often combined with other words, such as senile Alzheimer's, senile dementia, and senile plaques.

Senile can also be added as a descriptor and applied to other medical conditions, such as senile arthritis or senile osteoporosis. The word senile in these cases refers to the older age in which the condition developed and is completely unrelated to cognitive function.

Another common form of the word is senility.

The Use of the Word Senile

The common use of the word senile loosely references the loss of cognitive abilities or the inability to think clearly.

Senile was used more commonly in the past, especially when memory loss and confusion were thought of, by some, as a normal consequence of getting older. The view used to be that the body and the mind both could be expected to decline together as someone aged, and that poor mental functioning was just a normal part of aging.

An individual was often described as having "senile dementia" or "senile Alzheimer's," meaning that the disease and its associated mental decline developed in older age.

Although still occasionally used, this term has lost its popularity, partly because it has a negative, disrespectful tone, as in, "The old man is senile."

Science has shown that significant memory loss, disorientation, and confusion are not normal parts of aging, but rather are symptoms of neurocognitive disorders such as Alzheimer's diseasevascular dementia, frontotemporal dementia, or Lewy body dementia.

Senile is sometimes used to describe the plaques that build up in the brain as Alzheimer's disease progresses. These senile plaques, along with neurofibrillary tangles, are often described as the hallmarks of Alzheimer's disease,

What Is SDAT?

Senile dementia of Alzheimer's type (SDAT) is a medical diagnosis that previously was used to describe symptoms of dementia that were likely caused by Alzheimer's disease. The word senile here references the age of onset, which was considered senile if it had developed after the age of 65.

The descriptor "late-onset" (vs. early onset) is now more commonly used if the speaker is identifying the age of onset of dementia.

The word type was included in the diagnosis because Alzheimer's technically could only be definitively diagnosed following a brain autopsy after death, so the implication was that the symptoms appeared consistent with those of Alzheimer's disease.

According to the Diagnostic and Statistical Manual-V (DSM-V), SDAT is now coded diagnostically as either a major or minor neurocognitive disorder due to Alzheimer's disease.

While senility is a loosely used and somewhat inaccurate and negative reference to cognitive loss, dementia is an accepted medical term.

How Dementia Is Different From Senility

Dementia includes a broad range of brain conditions that cause a progressive decline in a person's ability to think and remember. Moreover, the loss of these abilities makes it increasingly difficult for people to function or care for themselves.

The most common causes of dementia include Alzheimer's disease, followed by vascular dementia, Lewy body dementia, and frontotemporal dementia. Other less common causes include Parkinson's associated dementia, Huntington's disease, tertiary syphilis, HIV-associated dementia, and Creutzfeldt–Jakob disease.

There is no cure for dementia, and the progression of the condition is typically slow. Medical professionals usually classify dementia by stage based on symptoms. 

Stages may be classified as follows:

  • Early-stage dementia is diagnosed when daily life is starting to become impacted. It is usually characterized by forgetfulness, inability to find words, repeating things, and difficulty in managing routine tasks like finances or shopping.
  • Middle-stage dementia will affect a person's ability to function both inside and outside of the home. A person will typically lose almost all new information within moments of receiving it and exhibit impairment of social judgment and general problem-solving, and will often get lost. Challenging behaviors often develop in mid-stage dementia.
  • Late-stage dementia is the stage where a person requires assistance with all activities of daily living, such as eating, bathing, and dressing. 

A Word From Verywell

In popular language, the terms senility and dementia often share the same space. But, in truth, senility may no longer have a place in the modern vocabulary given its inaccurate use and negative connotations.

Rather than reinforce the stigma of dementia through using the word senile, let's work together to reduce those stereotypes by being thoughtful about the terminology we use.

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4 Sources
  1. Alzheimer's Association. What is dementia?

  2. U.S. National Library of Medicine. MedlinePlus. Neurocognitive disorder. Reviewed February 27, 2018.

  3. Duong S, Patel T, Chang F. Dementia: What pharmacists need to know. Can Pharm J (Ott). 2017;150(2):118-129. doi:10.1177/1715163517690745

  4. Alzheimer's Association. Stages of Alzheimer's.

Additional Reading
  • American Psychiatric Association. (2013) Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. Arlington, Virginia: American Psychiatric Association.