Nearly 13 million Americans will have dementia by 2040 — nearly twice as many as today, a new report says.

The number of women with dementia is expected to rise from 4.7 million next year to 8.5 million in 2040. The number of men with dementia is projected to increase from 2.6 million to 4.5 million.

Over the next 20 years, the economic impact of Alzheimer's disease and other forms of dementia will be more than $2 trillion. Women will shoulder more than 80% of those costs, according to a report released Tuesday at the 2019 Milken Institute Future of Health Summit, in Washington, D.C.

"Longer life spans are perhaps one of the greatest success stories of our modern public health system," said lead author Nora Super, senior director of the Milken Institute Center for the Future of Aging.

"But along with this success comes one of our greatest challenges," she added in an institute news release. "Our risk of developing dementia doubles every five years after we turn 65; by age 85, nearly one in three of us will have the disease."

With no cure on the horizon, reducing the risk of dementia and its cost must be the focus, Super noted.

"Emerging evidence shows that despite family history and personal genetics, lifestyle changes such as diet, exercise and better sleep can improve health at all ages," she said.

The report recommends expanded research; programs to maintain and improve brain health; increased access to testing and early diagnosis, and services and policies that promote supportive communities and workplaces for people with dementia and their caregivers.

"As this important new report shows, dementia is one of the greatest public health challenges of our time," said Sarah Lenz Lock, the AARP's senior vice president for policy and brain health.

"It also demonstrates that we have the power to create change, whether by helping consumers maintain and improve their brain health, advancing research on the causes and treatment of dementia, or supporting caregivers who bear so much of the burden of this disease," Lock said in the news release.