The World Health Organization (WHO) has updated its fact sheet on dementia.
Dementia is a syndrome – usually of a chronic or progressive nature – in which there is deterioration in cognitive function (i.e. the ability to process thought) beyond what might be expected from normal ageing.
It affects memory, thinking, orientation, comprehension, calculation, learning capacity, language, and judgement. Consciousness is not affected. The impairment in cognitive function is commonly accompanied, and occasionally preceded, by deterioration in emotional control, social behaviour, or motivation.
Dementia is caused by a variety of diseases and injuries that primarily or secondarily affect the brain, such as Alzheimer’s disease or stroke.
Worldwide, around 47 million people have dementia, with nearly 60% living in low- and middle-income countries. Every year, there are 9.9 million new cases.
The estimated proportion of the general population aged 60 and over with dementia at a given time is between 5 to 8 per 100 people.
The total number of people with dementia is projected to near 75 million in 2030 and almost triple by 2050 to 132 million, with most of the increase occurring in low and middle-income countries.
The signs and symptoms linked to dementia can be understood in three stages.
Early stage: the early stage of dementia is often overlooked, because the onset is gradual. Common symptoms include:
- losing track of the time
- becoming lost in familiar places.
Middle stage: as dementia progresses to the middle stage, the signs and symptoms become clearer and more restricting. These include:
- becoming forgetful of recent events and people’s names
- becoming lost at home
- having increasing difficulty with communication
- needing help with personal care
- experiencing behaviour changes, including wandering and repeated questioning.
Late stage: the late stage of dementia is one of near total dependence and inactivity. Memory disturbances are serious and the physical signs and symptoms become more obvious. Symptoms include:
- becoming unaware of the time and place
- having difficulty recognizing relatives and friends
- having an increasing need for assisted self-care
- having difficulty walking
- experiencing behaviour changes that may escalate and include aggression.
Alzheimer’s disease is the most common form of dementia and may contribute to 60–70% of cases.
Other major forms include
- vascular dementia,
- dementia with Lewy bodies (abnormal aggregates of protein that develop inside nerve cells), and
- a group of diseases that contribute to frontotemporal dementia (degeneration of the frontal lobe of the brain).
The boundaries between different forms of dementia are indistinct and mixed forms often co-exist.
There is no treatment currently available to cure dementia or to alter its progressive course.
Although age is the strongest known risk factor for dementia, it is not an inevitable consequence of ageing – young onset dementia (defined as the onset of symptoms before the age of 65 years) accounts for up to 9% of cases.
Some research has shown a relationship between the development of cognitive impairment and life-style related risk factors that are shared with other noncommunicable diseases. These risk factors include
- physical inactivity,
- unbalanced diets,
- tobacco use and
- harmful use of alcohol,
- diabetes, and
- midlife hypertension.
Additional modifiable risk factors include
- low educational attainment,
- social isolation, and
- cognitive inactivity.
Dementia is overwhelming for the families of affected people and for their carers.
In 2015, the total global societal cost of dementia was estimated to be US$ 818 billion. This corresponds to 1.1% of the worldwide gross domestic product (GDP).
Link to the updated fact sheet:
Link to infographic on dementia (English , French and Spanish) [PDF]:
Link to WHO document ‘Dementia- A Public Health Priority’ (2012) (Multiple languages):
Link to technical information on dementia:
Link to 10 facts on dementia: