Last edited 09/2018 and last reviewed 08/2023

Dementia may be defined as a progressive and largely irreversible clinical syndrome that is characterized by global deterioration in intellectual function, behaviour and personality in the presence of normal consciousness and perception (1).

The most common types of dementia are:

  • Alzheimer's disease, vascular dementia, mixed dementia, dementia with Lewy bodies and frontotemporal dementia (2)

Dementia is a progressive condition, which means that the symptoms will gradually get worse. This progression will vary from person to person and each will experience dementia in a different way - people may often have some of the same general symptoms, but the degree to which these affect each person will vary (2).

Many patients have preserved positive personality traits and personal attributes but the following features may become evident as the disease progresses:

  • memory loss, language impairment, disorientation, changes in personality, difficulty in carrying out daily activities, self-neglect
  • psychiatric symptoms - apathy, depression or psychosis
  • unusual behaviour - aggression, sleep disturbance or disinhibited sexual behaviour (1)

Dementia can be divided into:

  • young-onset dementia – formerly known as “pre-senile dementia”, refers to patients who develop dementia before the age of 65 years
  • late-onset dementia – previously known as “senile dementia”, refers to patients who develop dementia after the age of 65 years (1)

Several risk factors responsible for the development of dementia have been recognized (1).

  • non modifiable risk factors
    • age – advancing age is the most important risk factor in developing dementia
    • learning disabilities – in people with Down’s syndrome, dementia develops 30–40 years earlier than in a normal person
    • gender – rate of dementia is higher in women than in men (specially for Alzheimers disease)
    • genetic factors
  • modifiable risk factors
    • alcohol consumption  
    • smoking – particulary for Alzheimers
    • obesity
    • hypertension
    • hypercholesterolaemia
    • head injury
    • education and mental stimulation (1)

The most common causes of dementia are age-related neurodegenerative processes. Dementia is becoming an increasing problem as the population ages.