Experts are predicting that the number of people worldwide living with Alzheimer's disease will quadruple by 2050.
Almost half of them (43%) will need high-level care as the "global epidemic" takes hold, they said.
The estimated 26 million people across the world currently living with the condition will grow to more than 106 million by 2050, according to US researchers.
In the UK, around 1.7 million people will be affected by the condition by that date, the Alzheimer's Society said.
There are currently 700,000 people with dementia in the UK, and 60,000 people die from it every year.
The US research, which blames an increasingly aging population for the estimated growth, has been presented at the International Conference on the Prevention of Dementia in Washington DC.
Professor Ron Brookmeyer, from the Bloomberg School of Public Health in Maryland, said: "We face a looming global epidemic of Alzheimer's disease as the world's population ages.
"By 2050, one in 85 persons worldwide will have Alzheimer's disease. However, if we can make even modest advances in preventing Alzheimer's disease or delay its progression, we could have a huge global public health impact."
Neil Hunt, chief executive of the Alzheimer's Society, said: "The Alzheimer's Society's recent Dementia UK report put the current cost of the condition to this country at £17bn every year.
"It also predicted a rise in the number of those affected to 1.7 million by 2050.
"A national dementia strategy must consider the global scale of Alzheimer's disease and other types of dementia."