Southern Cross Medical Library

Southern Cross Medical Library

Dementia is a term for a group of symptoms that indicate a loss of brain function. Treatment depends on the type of dementia but 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 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. Dementia is thought to affect around 70,000 New Zealanders.

A degree of memory loss is reasonably common 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 in the brain that interferes with nerve cells' ability to communicate with each other.

Different types of progressive dementia, and their causes, include:

  • Alzheimer's disease: the most common form of dementia in people aged over 65 years. Abnormal protein formations, known as plaques and tangles, are often found in the brains of people with Alzheimer's disease
  • Vascular dementia: the result of damage to the blood vessels in the brain, which can be caused by stroke
  • Lewy body dementia: presence of abnormal clumps of protein called Lewy bodies in parts of the brain involved in thinking, memory and movement. Lewy bodies are also found in the brains of people with Alzheimer's disease and Parkinson's disease
  • Frontotemporal dementia: degeneration of nerve cells in areas of the brain that are associated with personality, behaviour, and language
  • Mixed dementia: a combination of Alzheimer's disease, vascular dementia, and Lewy body dementia
  • Dementia associated with traumatic brain injury (notably, repeated concussions) 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
  • Endocrine abnormalities: high or low levels of thyroid hormone
  • Metabolic problems: low blood sugar; high levels of calcium in the blood; or an impaired ability to absorb vitamin B12
  • Nutritional deficiencies: dehydration and lack of certain dietary vitamins
  • Reactions to medications: certain medications or an interaction of several different medications
  • 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
  • Insufficient oxygen reaching brain or body tissues, e.g. due to severe asthma, heart attack, or carbon monoxide poisoning.

Risk factors

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

In general, the most common signs and symptoms of dementia are related to cognitive changes (i.e. knowing, thinking, learning, understanding) and psychological changes (i.e. emotions and behaviour):

Cognitive 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.

Psychological changes:

  • Changes in personality or character
  • Behaviour that is inappropriate
  • Mood changes including depression and anxiety
  • Agitation
  • 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.

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
  • 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 some forms of protein clumps are present in the brain
  • Laboratory tests: blood tests can detect other causes of impaired brain function, such as vitamin B12 deficiency, underactive thyroid (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 work by boosting brain levels of a particular chemical messenger involved in memory and judgment. Side effects may include nausea, vomiting, and diarrhoea
  • Memantine works by regulating the activity of another chemical messenger in the brain involved in learning and memory. Dizziness is a common side effect
  • Other medications may be prescribed to treat other symptoms or conditions, such as anxiety, depression, sleep disturbances, or agitation.

Lifestyle changes

Certain lifestyle changes may help to slow down or prevent the onset of progressive dementia:

  • Physical exercise: increasing evidence suggests that daily exercise 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.


Mayo Clinic (2017). Dementia (Web Page). Rochester, NY: Mayo Foundation for Medical Education and Research. [Accessed: 27/08/18]
MedlinePlus (2018). Dementia due to metabolic causes (Web Page). Bethesda, MD: US National Library of Medicine (NIH). [Accessed: 28/08/18]
Ministry of Health (2018). Dementia (Web Page). Wellington: New Zealand Government Ministry of Health. [Accessed: 27/08/18]
NHS Choices (2015). Dementia guide (Web Page). Redditch: National Health Service (NHS)
England. [Accessed: 27/08/18]
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

Go to our Medical Library Index Page to find information on other medical conditions.


The purpose of the Southern Cross Medical Library is to provide information of a general nature to help you better understand certain medical conditions. Always seek specific medical advice for treatment appropriate to you. This information is not intended to relate specifically to insurance or healthcare services provided by Southern Cross.