What Is Dementia? And What Are Signs and Symptoms of Dementia?

Dementia is not a single disease in itself, but a general term to describe symptoms such as impairments to memory, communication and thinking.

While the likelihood of having dementia increases with age, it is not a normal part of aging. Before we had today's understanding of specific disorders, "going senile" used to be a common phrase for dementia ("senility"), which misunderstood it as a standard part of getting old.

Light cognitive impairments, by contrast, such as poorer short-term memory, can happen as a normal part of aging (we slowly start to lose brain cells as we age beyond our 20s3). This is known as age-related cognitive decline, not dementia, because it does not cause the person or the people around them any problems.1 Dementia describes two or more types of symptom that are severe enough to affect daily activities.

Symptoms that are classed as "mild cognitive impairment" - which, unlike cognitive decline, are not a normal part of aging - do not qualify as dementia either, since these symptoms are not severe enough.1 For some people though, this milder disease leads to dementia later on.

An analysis of the most recent census estimates that 4.7 million people aged 65 years or older in the US were living with Alzheimer's disease in 2010.5 The Alzheimer's Association has used this analysis to number-crunch the extent of the disorder in its 2013 report. It estimates that:

Just over a tenth of people aged 65 years or more have Alzheimer's disease.

This proportion rises to about a third of people aged 85 and older.

The non-profit organization says Alzheimer's accounts for between 60% and 80% of all cases of dementia, with vascular dementia caused by stroke being the second most common type.

Signs and symptoms
Memory loss in dementia can be serious enough for the person to forget where they are, even on their home street.
The symptoms of dementia experienced by patients, or noticed by people close to them, are exactly the same signs that healthcare professionals look for. Therefore, detailed information on these is given in the next section about tests and diagnosis.

A person with dementia may show any of the following problems, mostly due to memory loss - some of which they may notice (or become frustrated with) themselves, while others may only be picked up by carers or healthcare workers as a cause for concern. The signs used to compile this list are published by the American Academy of Family Physicians (AAFP) in the journal American Family Physician:6

Recent memory loss - a sign of this might be asking the same question repeatedly, forgetting about already asking it.
Difficulty completing familiar tasks - for example, making a drink or cooking a meal, but forgetting and leaving it.
Problems communicating - difficulty with language by forgetting simple words or using the wrong ones.
Disorientation - with time and place, getting lost on a previously familiar street close to home, for example, and forgetting how they got there or would get home again.
Poor judgment - the AAFP says: "Even a well person might get distracted and forget to watch a child for a little while. People with dementia, however, might forget all about the child and just leave the house for the day."
Problems with abstract thinking - for example, dealing with money.
Misplacing things - including putting them in the wrong places and forgetting about doing this.
Mood changes - unlike those we all have, swinging quickly through a set of moods.
Personality changes - becoming irritable, suspicious or fearful, for example.
Loss of initiative - showing less interest in starting something or going somewhere.