Dementia is a term that describes a group of symptoms associated with impaired memory and thinking skills. Collectively, these symptoms indicate a loss of brain function. Treatment depends on the type of dementia, although most types are incurable.
Dementia is not a specific disease. It is a general term that covers a set of related symptoms associated with a decline in memory, thinking, understanding, and judgement. There are different types of dementia:
- Progressive dementias are when changes in brain function worsen with time and are permanent. With progressive dementia, the symptoms eventually become severe enough that they reduce a person's ability to perform daily activities and to socialise
- Some forms of dementia (or conditions that cause dementia-like symptoms) can improve with treatment and are sometimes referred to as reversible dementia.
While dementia is more common in people over 65 years of age, it is not part of the normal ageing process. Some degree of memory loss is not uncommon among older people but, in the absence of an underlying medical condition, that’s not considered to be dementia.
Dementia can affect people as young as 45 years. Dementia that develops before the age of 65 years is referred to as early-onset dementia.
Dementia is caused by damage to nerve cells in the brain, which interferes with their ability to communicate with each other. Dementia manifests differently in different people depending on the area of the brain that is affected.
Different types of progressive dementia include:
- Alzheimer's disease: is the most common cause of dementia in people aged over 65 years. The cause of Alzheimer's disease isn't known but abnormal protein formations, known as plaques (beta-amyloid) and tangles (tau protein), are often found in the brains of people with Alzheimer's disease
- Vascular dementia: is the second most common type of dementia. It occurs as a result of damage to the blood vessels in the brain, which can be caused by stroke
- Lewy body dementia: is characterised by the presence in the brain of abnormal clumps of protein called Lewy bodies. Lewy bodies are also found in the brains of people with Alzheimer's disease and Parkinson's disease
- Frontotemporal dementia: is a group of diseases in which there is degeneration of nerve cells in areas of the brain that are associated with personality, behaviour, and language
- Mixed dementia: is a combination of Alzheimer's disease, vascular dementia, and Lewy body dementia
- Dementia associated with traumatic brain injury or disorders including Parkinson’s disease, Huntington’s disease and Creutzfeldt-Jakob disease.
Different types of dementia or dementia-like symptoms that can be reversed with treatment include:
- Infection: fever and other consequences of the body fighting off an infection can produce symptoms that resemble dementia
- Immune system disorders: such as multiple sclerosis, which result from the body's immune system attacking nerve cells
- Endocrine abnormalities: high (thyrotoxicosis) or low (hypothyroidism) levels of thyroid hormone
- Metabolic problems: low blood sugar (hypoglycaemia), which is a common consequence of diabetes treatment; high levels of calcium in the blood, which is often due to hyperparathyroidism; or an impaired ability to absorb vitamin B12
- Nutritional deficiencies: dehydration and lack of dietary vitamin B1 (thiamine), which is common in chronic alcoholism, vitamin B6, and vitamin B12
- Reactions to medications: certain medications or an interaction of several different medications
- Subdural haematomas: bleeding on the brain, which is common after a fall in elderly people.
- Poisoning: exposure to heavy metals (e.g., lead, arsenic) or other poisons (e.g., pesticides), alcohol abuse, or recreational drug use
- Brain tumours: although uncommon, damage caused by a brain tumour can result in dementia
- Anoxia/hypoxia: this occurs when insufficient oxygen reaches organ tissues, e.g. due to severe asthma, heart attack, or carbon monoxide poisoning.
Many factors can increase the risk of a person developing dementia, including:
- Age: while dementia isn’t a normal part of ageing, the risk of developing it does increase as you age
- Family history: certain genetic mutations put people at higher risk of dementia.
- Down syndrome: many people with Down syndrome develop early-onset Alzheimer's disease
- Mild cognitive impairment: people who have difficulties with memory but without loss of daily function are at higher risk of dementia
- Cardiovascular risk factors: including high blood pressure, high blood cholesterol, and obesity.
- Depression: when it emerges in late life, depression might indicate the development of dementia
- Diabetes: is associated with an increased risk of dementia, especially diabetes that is poorly controlled
- Heavy alcohol use and smoking
- Sleep apnoea: people who snore and frequently stop breathing while asleep may experience reversible memory loss
- Traumatic brain injury (e.g. from falls, vehicle accidents or sports) can have direct effects and increase future risk of developing dementia.
Signs and symptoms
Dementia symptoms differ depending on the cause. In general, the most common signs and symptoms are those related to cognitive changes (i.e. knowing, thinking, learning, understanding) and psychological changes (i.e. emotions and behaviour) changes:
- Memory loss
- Problems with language and communication
- Reduced ability to perform complex tasks
- Impaired reasoning or problem-solving ability
- Struggling to plan and organize things
- Impaired judgement and impulse control
- Confusion and disorientation.
- Changes in personality or character
- Behaviour that is inappropriate
- Mood changes including depression and anxiety
- Paranoia and hallucinations.
In progressive dementia, a person’s symptoms get worse with time and they may eventually need help with daily living activities such as dressing, toileting, and showering.
Diagnosis of dementia is based on taking a medical history, a physical examination, laboratory tests, and the presence of the characteristic changes in thinking, daily functioning, and behaviour.
A diagnosis of dementia will consider the degree to which impaired mental functions interfere with daily living. The core mental functions are: memory, language skills, ability to concentrate, reasoning and judgement, and visual perception.
Multiple tests are likely to be needed to confirm a diagnosis of dementia and to help determine the type of dementia. These tests include:
- Cognitive and neuropsychological tests: to evaluate specific components of cognitive function, e.g., memory, reasoning and judgment, language skills, and attention. A simple screening tool often used by GPs is the General Practitioner Assessment of Cognition (GPCOG).
- Brain scans: computed tomography (CT) or magnetic resonance imaging (MRI) may be used to check for evidence of stroke, bleeding, tumour, or hydrocephalus (fluid on the brain), which can cause dementia-like symptoms. A positron emission tomography (PET) scan is able to show whether amyloid protein is present in the brain.
- Laboratory tests: blood tests can detect other causes of impaired brain function, such as vitamin B12 deficiency, hypothyroidism, elevated blood calcium levels.
- Psychiatric evaluation: can determine whether depression or another mental health condition is contributing to symptoms.
Although a doctor can determine that a person has dementia with a high level of confidence, determining the specific type of dementia is more challenging, mainly because the symptoms and brain changes of the different types of dementia can overlap.
Getting an early diagnosis is important because it provides the opportunity to obtain the greatest benefit from available treatments and to plan for the future. Getting an early diagnosis is also recommended because some causes of dementia symptoms are reversible.
There is no cure for progressive dementia, nor any treatments that stop its progression. However, medications may slow the progress of some forms of dementia, and improve quality of life and the ability to perform daily tasks.
The following medications are used to temporarily reduce the symptoms of progressive dementia:
- Cholinesterase inhibitors: these medications, which include donepezil, rivastigmine, and galantamine, work by boosting brain levels of acetylcholine, which is a chemical messenger involved in memory and judgment. Side effects may include nausea, vomiting, and diarrhoea
- Memantine: this medication works by regulating the activity of glutamate, which is a chemical messenger in the brain involved in learning and memory. Dizziness is a common side effect of memantine
- Other medications: these may be prescribed to treat other symptoms or conditions, such as anxiety, depression, sleep disturbances, or agitation.
Certain lifestyle changes may help to slow down or prevent the onset of progressive dementia:
- Physical exercise: increasing evidence suggests that daily exercise (aerobic or resistance) protects the brain from dementia, possibly by increasing blood flow to the brain
- Diet: eating healthy food benefits both the body and brain. Evidence suggests that a heart-healthy diet, such as the Mediterranean diet, also helps to reduce the risk of developing dementia
- Socialising: staying socially interactive and engaging in social activities (such as dancing, painting, and cooking classes) helps to keep the brain stimulated.
- Brain exercises: reading, crosswords, word puzzles, and memory games keep the mind active
- Drink less alcohol and quit smoking.
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O’Toole, M.T. (Ed.) (2013). Dementia. Mosby’s Dictionary of Medicine, Nursing & Health Professions (9th ed.). St Louis, MI: Elsevier Mosby.
Updated: August 2018