In 2010, there were just 4.7 million people with Alzheimer's disease in the United States.
The researchers who made the projections attribute the predicted increase to the high numbers of "baby boomers" - the especially large generation born after World War II - who are now reaching old age.
More than half of those with the disease by 2050, some seven million people, will be 85 or older, the researchers said.
The trend has been noted in the past, but the new study updates the figures, and highlights the need for doctors and others to get in gear in anticipation, said co-author Jennifer Weuve, from the Rush University Medical Center in Chicago.
The high numbers of Alzheimer's sufferers "will place a huge burden on society, disabling more people who develop the disease, challenging their caregivers, and straining medical and social safety nets," Weuve explained.
"Our study draws attention to an urgent need for more research, treatments and preventive strategies to reduce this epidemic," she added.
For the study, the authors analyzed nearly two decades of data from 10,802 African Americans and whites, aged 65 and older, living in Chicago.
Every three years from 1993 to 2011, the study participants were interviewed and assessed for dementia, while taking into account age, race, and educational level.
The researchers also factored in US death rates, education, and current and future population estimates from the US census bureau.
Source: Agence France-Presse