A report on the global impact of dementia says costs associated with the illness will reach an estimated $US604 billion this year.
The World Alzheimer Report says this is more than the revenue of Wal-Mart or Exxon Mobil.
The study calls dementia - an incurable and degenerative disease of the mind - the most significant health and social crisis of the century because of the global cost.
Professor Martin Prince of King's College, London, also says there will also be sharp increases in the illness in developing countries.
The authors want the World Health Organisation to make dementia a world priority.
The BBC reports there are many types of dementia, but Alzheimer's disease, which accounts for two thirds of cases, is the most well-known.
A large part of the problem is people living longer. As life expectancy goes up around the world there will be more people who will develop dementia.
The number of people with dementia is expected to double by 2030 and more than triple by 2050.