The number of people with dementia will almost double every 20 years across the world, researchers predicted.
British experts calculated figures for the number of people worldwide who will suffer dementia, including Alzheimer's disease, in the future.
The fact people are living longer than ever before is a major factor driving the increasing incidence of dementia.
The study estimates that the number of people with dementia and Alzheimer's will almost double every 20 years worldwide, to 65.7 million in 2030 and 115.4 million in 2050.
A total of 35.6 million people will have dementia in 2010, the report said.
At present, some 700,000 people in the UK have a form of dementia, with more than half of these suffering from Alzheimer's.
It has previously been predicted that in less than 20 years nearly a million people in the UK will be living with dementia, soaring to 1.7 million people by 2051.
The latest research - contained in the World Alzheimer's Report 2009 - is published by Alzheimer's Disease International (ADI).
It said that, over the next 20 years, the number of people with dementia is expected to increase by 40% in Europe (44% in Western Europe), 63% in North America, 77% in southern Latin American and 89% in developed Asia Pacific countries.
But the increase will be much sharper in other countries, including 117% in East Asia, 107% in South Asia, 134 to 146% in the rest of Latin America, and 125% in North Africa and the Middle East.
