Dementias are the most common cause of psychological problems in the elderly. The greatest risk factor for developing dementia is age. The most common type of dementia is Alzheimer's disease. Other common types include vascular dementia, dementia with Lewy bodies, and frontotemporal dementia. Less common causes include normal pressure hydrocephalus, Parkinson's disease dementia, syphilis, HIV, and Creutzfeldt-Jakob disease.
Alzheimer's disease accounts for approximately 60 percent of dementia in old age. It is estimated that this condition afflict from 5 to 10 percent of people 65 years of age or older, and it accounts for the most striking rise in dementia incidence in the very old. The rate of Alzheimer's disease is around 20-40% in those older than 85. Rates are slightly higher in women than men above the age of 65 and later.
Although, this means there is 90-95% chance that someone over 65 will have normal cognitive functions and no signs of dementia, the rate of incidence in the population is still high compared to other illnesses. In those over 85 years of age, one in five may have that condition which is a big health problem. The incidence of dementia increases exponentially with age, doubling with every 6.3 year increase in age.
Dementia impacts not only individuals with dementia, but also their carers and the wider society. Among people aged 60 years and over, dementia is ranked the 9th most burdensome condition according to the 2010 Global Burden of Disease (GBD) estimates.
Dementia of the Alzheimer's type and related dementias cost the United Kingdom 26 billions each year. The figure is 355 billion dollars in the United States. This includes direct costs (i.e., actual expenditures) and indirect costs (i.e., resource losses not involving expenditures).
An estimated six million U.S. citizens have Alzheimer's disease, while 850,000 people are living with dementia in the United Kingdom. Worldwide, around 50 million people have dementia, and there are nearly 10 million new cases every year. The incidence of that disease is increasing every year. It is projected to reach 82 million in 2030 and 152 milions in 2050. Much of this increase is attributable to the rising numbers of people with dementia living in low- and middle-income countries. Worldwide the cost of dementia in 2015 was put at US$818 billion.
In 2016 dementia resulted in about 2.4 million deaths, up from 0.8 million in 1990. In 2020 it was reported that dementia was listed as one of the top ten causes of death worldwide. Another report stated that in 2016 it was the fifth leading cause of death.
On the other hand, as more people are living longer, dementia is becoming more common. For people of a specific age, however, it may be becoming less frequent in the developed world, due to a decrease in preventable risk factors made possible by greater financial and educational resources. It is one of the most common causes of disability among the old.