Causes of Memory Loss and Dementia

Authored by , Reviewed by Dr John Cox on | Certified by The Information Standard

Everybody forgets things from time to time. In general, the things that you tend to forget most easily are the things that you feel do not matter as much.

The things that you tend to remember most easily are the things that are important to you - for example, a special birthday. However, some people just seem to have a better memory than others, and some people are more forgetful than others.

There are certain situations that can affect your memory and make you become more forgetful than you normally are. They can include the following.

Poor concentration

If your concentration is poor then you do not notice things as much, and do not retain things as much as you would normally. Poor concentration can be a result of simply being bored or tired. However, it can also be a symptom of depression and anxiety.

Depression

As well as poor concentration, some people with depression also have slowed thinking. This can cause memory problems until the depression clears. Do tell a doctor if you think that you are depressed, as treatment often works well. Other symptoms of depression include:

  • A low mood for most of the time.
  • Loss of enjoyment and interest in life.
  • Abnormal sadness.
  • Weepiness.
  • Feelings of guilt or of being useless.
  • Poor motivation.
  • Sleeping problems.
  • Tiredness.
  • Difficulty with affection.
  • Poor appetite.
  • Being irritable or restless.

Physical illness

If you feel ill, this can affect concentration and memory. Certain illnesses can directly affect the way your brain works. For example, an underactive thyroid can slow down your body's functions, including your brain, and can make you more forgetful. Infections such as a chest infection or a urine infection can also cause sudden confusion and memory problems, particularly in older people.

Medicines

Certain medicines can cause confusion and memory problems in some people. For example, some sedative medicines, some painkilling medicines, some medicines that are used to treat Parkinson's disease, or steroid medicines. Also, if you are taking lots of different medicines, this can increase the risk of them interacting with each other, causing problems, including confusion and memory problems.

Age

As everyone gets older, it often becomes harder to remember things. This is called age-associated memory impairment. Many people over the age of 60 have this common problem, and it is not dementia. For example, it tends to be harder to learn new skills the older you become, or you may more easily forget the names of people you have recently met. It is thought that the more you use your brain when you are older, the more it may counter the development of this age-related decline in memory function. So, doing things such as reading regularly, quizzes, crosswords, memorising plays or poetry, learning new skills, etc, may help to keep your memory in good shape.

Dementia is a common problem. According to figures provided by the Alzheimer's Society, there are currently 835,000 people with dementia in the UK. It is estimated that there will be over two million by 2050. The older you are the higher chance there is of getting dementia. Between the ages of 65 and 74, 1-3 people in 100 will have dementia. By the age of 95, 41 people in 100 will have it.

However, dementia is not a normal part of ageing. It is different to the age-associated memory impairment that is common in older people. Rarely, dementia affects younger people. Dementia is said to be early-onset (or young-onset) if it comes on before the age of 65.

There are some groups of people who are known to have a higher risk of developing dementia. These include people with:

  • Down's syndrome or other learning disabilities. People with Down's syndrome are more likely to develop Alzheimer's disease.
  • Parkinson's disease. As many as half of people with Parkinson's disease may develop dementia.
  • Risk factors for cardiovascular disease (anginaheart attackstroke and peripheral arterial disease). The risk factors for cardiovascular disease (high blood pressure, smoking, a high cholesterol level, lack of exercise, etc) are risk factors for all types of dementia, not just blood vessel dementia (vascular dementia).
  • A past history of a stroke.
  • A history of drinking excess alcohol.
  • A family history of dementia. There is a small extra risk of getting dementia if you have a mother, father or sibling with dementia. Dementia also seems to run in some families so there may be some genetic factors that can make someone more likely to develop dementia. We do know that a few of the more rare causes of dementia can be inherited (can be passed on through genes in your family).
  • Severe psychiatric problems such as schizophrenia or severe depression. It is not clear why this is the case.
  • A past history of a head injury.
  • Lower intelligence. Some studies have shown that people with a lower IQ and also people who do not have very high educational achievement are more likely to develop dementia.
  • A limited social support network.
  • Low physical activity levels. A lack of physical activity can increase your risk of dementia. See separate leaflet called Physical Activity for Health for more details.

Most cases are caused by Alzheimer's disease, vascular dementia, or dementia with Lewy bodies (DLB). All these types of dementia cause similar symptoms but some features may point to a particular cause. However, it may not be possible to say what is causing the dementia in every case.

Alzheimer's disease

This is the most common type of dementia, causing at least half of all cases, possibly up to three quarters. It is named after the doctor who first described it. In Alzheimer's disease the brain shrinks (atrophies) and the numbers of nerve fibres in the brain gradually reduce. The amount of some brain chemicals (neurotransmitters) is also reduced - in particular, one called acetylcholine. These chemicals help to send messages between brain cells.

Tiny deposits called plaques also form throughout the brain. It is not known why these changes in the brain occur, or exactly how they cause dementia. Alzheimer's disease gradually progresses (worsens) over time as the brain becomes more and more affected.

Blood vessel dementia (vascular dementia)

This causes about a fifth of all cases of dementia. It is due to problems with the small blood vessels in your brain. The most common type is called multi-infarct dementia. In effect, this is like having many tiny strokes, that otherwise go unrecognised, throughout the thinking part of the brain.

A stroke occurs when a blood vessel blocks and stops the blood getting past. So, the section of brain supplied by that blood vessel is damaged or dies (an infarct occurs). After each infarct, some more brain tissue is damaged. So, a person's mental ability gradually declines. Vascular dementia can also sometimes happen after a more major stroke.

The risk of developing vascular dementia is increased by the same things that increase the risk of stroke. For example: high blood pressure, smoking, a high cholesterol level, lack of exercise, etc. See separate leaflet called Preventing Cardiovascular Diseases for more details. However, it is now thought that some of these vascular risk factors may also be involved in the development of Alzheimer's disease and other types of dementia as well.

Lewy body dementia/dementia with Lewy bodies (DLB)

This causes 10 to 15 in every 100 cases of dementia. Lewy bodies are tiny abnormal protein deposits that develop in nerve cells in the brain of people with this condition. It is not clear why the Lewy bodies develop but they interfere with the normal working of the brain.

If Lewy bodies develop in a part of the brain called the brain stem, as well as symptoms of dementia, someone may also develop symptoms similar to Parkinson's disease. For example, stiffness, slowness of movement and a shuffling walk with difficulty in starting, stopping, and in turning easily.

Mixed dementia

Some people can have a degree of two different types of dementia at the same time. For example, both Alzheimer's disease and vascular dementia, or both Alzheimer's disease and DLB. This is known as mixed dementia. However, in most cases of mixed dementia, there is usually one of the causes for dementia that is thought to be the main (predominant) cause. In this situation, treatment is aimed at the predominant cause of dementia.

Other causes of dementia

There are over 60 diseases which can cause dementia. Many are rare and, in many, the dementia is just part of other problems and symptoms. In most cases the dementia cannot be prevented or reversed. However, in some disorders the dementia can be prevented, or stopped from getting worse if treated. For example, some cases of dementia are caused by alcohol abuse, infections such as syphilis, or some vitamin deficiencies, all of which can be treated.

Further reading and references

What are the different types of dementia?
How to tackle dementia stigma
How does diet affect dementia?

My dad now 71 has always been forgetful, blames it on work stress and thatHe sometimes has sleep disorder which I read online is RBD where he jumped from a bed few years ago and broke a finger, and...

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