Mild cognitive impairment (MCI)

The brain gets smaller and communication between cells becomes less effective as we get older and some cognitive (conscious intellectual activity such as thinking, reasoning, or remembering) changes happen as a result. Some people experience changes which are worse than you would expect as part of the normal ageing process and some people develop dementia.

Below is a quick summary of the cognitive changes a person may experience as they get older.

  • Normal age related cognitive decline – minor cognitive changes, which are subtle and barely noticeable, that happen as part of normal ageing.
  • Mild cognitive impairment (MCI) – where someone has problems with their memory and/or thinking skills which are noticeable to themselves or others but do not have a significant impact on their daily lives.
  • Dementia – where someone has a set of symptoms which may include memory loss, difficulties with thinking, problem-solving or language, which have become severe enough to affect daily life.

Note: Although dementia and MCI generally affects people over 65, these conditions can occur in people under 65, generally known as young-onset or early-onset dementia/cognitive impairment.

Normal age related cognitive decline

Listed below are some of the cognitive changes that may happen as a normal process of ageing; although some cognitive abilities are resilient to ageing such as vocabulary.

  • Cognitive speed.
  • Memory performance.
  • Conceptual reasoning (the ability to understand a situation or problem by identifying patterns or connections, and addressing key underlying issue).
  • Visual perceptual abilities.

These changes are subtle and barely noticeable and may include temporarily forgetting a word or occasionally misplacing an item.

Mild cognitive impairment (MCI)

Some people have minor problems with cognition (their mental processes such as memory or thinking skills) which are worse than you would normally expect in someone of their age. These changes are serious enough to be noticed by the individuals experiencing them or to other people.

This is known as mild cognitive impairment (MCI), as it is not severe enough to be classed as dementia, because it does not impact on their daily lives or their ability to function independently.

There are 2 types of MCI:

  • Amnestic MCI – where memory loss is the main symptom.
  • Nonamnestic MCI – where other thinking abilities such as organising and planning,
    reasoning, learning or judgement may be affected but memory remains intact.

Although it is not inevitable, a person with MCI is more likely to develop dementia. In some cases, experts believe MCI is a result of brain changes occurring in the very early stages of dementia.

In other cases however, MCI will turn out to have a different, often treatable, cause such as depression, anxiety or stress. MCI could also be caused by a physical illness such as constipation or urine infection, a vitamin or thyroid deficiency or the side effects of medication. In these cases the diagnosis will be whatever is causing the cognitive impairment i.e. depression or thyroid deficiency rather than MCI.


Once the symptoms of cognitive decline become so serious that it interferes with a person’s daily functioning then dementia is the appropriate diagnosis.

There are many diseases or conditions which cause dementia. Most types of dementia are caused by irreversible diseases such as Alzheimer’s disease or dementia with Lewy bodies.

However some dementias are caused by reversible conditions, such as a vitamin or thyroid deficiency, where recovery can be possible after treatment.

Normal age related cognitive decline vs dementia

The table below highlights the types of memory lapses you would expect due to normal age related cognitive decline versus the more serious symptoms that may suggest dementia.

Mild Cognitive Impairment


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