Dementia cases are expected to more than double in the coming decades, with the risk beginning as early as 55, and the lifetime risk of developing dementia is 42 percent, according to a new study.

A new study found that dementia cases in the United States are projected to double from more than 500,000 in 2020 to about 1 million by 2050.

Dementia cases in the U.S. are expected to double by 2060, with an estimated one million people diagnosed per year, according to a new study led by Johns Hopkins University and other institutions.

A new study found an increased risk of dementia in older Americans, with the risk among Black Americans even greater. NBC News' Anne Thompson reports on what doctors say can help lower the risk of dementia.