As baby boomers enter their golden years, the number of people afflicted with Alzheimer's disease is expected to reach 13.8 million by 2050 -- millions more than previously anticipated, said a new study in the journal Neurology.

If researchers can't find a way to reduce the prevalence of the disease, the cost to care for all of these patients could top $1 trillion a year, experts say.

Alzheimer's is a progressive brain disease that damages patients' memory and cognitive skills, ultimately leaving them unable to care for themselves. Scientists aren't sure how it starts, but they believe it causes plaques and tangles to form in the brain, slowly killing neurons and causing the brain to shrink. Between 60 and 80 percent of dementia cases are believed to be a consequence of Alzheimer's, the Alzheimer's Association said.

The risk of developing the disease rises with age. So while deaths from breast and prostate cancer, heart disease, stroke and HIV all fell between 2000 and 2008, the number of Alzheimer's-related deaths grew by two-thirds in the same period -- a macabre result of people living longer than ever before. Doctors, researchers and public health experts are already bracing for an onslaught of new patients by developing drugs and preparing caregivers for the emotional and physical stress.

"This is an issue that's going to touch each of us personally or someone that we know," said Lora Connolly, director of the California Department of Aging, which expects to be serving as many as 1.2 million patients with Alzheimer's or dementia in the state by 2030.

The projections released last week are based on a study of 1,913 senior citizens from the Chicago area who were evaluated for Alzheimer's between 1997 and 2011. Researchers from the Rush Institute for Healthy Aging evaluated the volunteers every three years, conducting in-home interviews and clinical checkups to see whether they were developing symptoms of dementia. Participants were all at least 65 years old and came from a variety of backgrounds.

A total of 402 people were newly identified with Alzheimer's during the study period, and, as expected, the incidence increased with age. The researchers used models to extrapolate their results to the U.S. population and make projections for 2050. They calculated that 1.3 million people between ages 65 and 74 would have Alzheimer's, along with 5.4 million 75- to 84-year-olds and 7 million people older than 85. The grand total was 13.8 million patients.

Put another way, the researchers projected that 3.3 percent of 65- to 74-year-olds, 18.5 percent of 74- to 84-year-olds and 36.6 percent of those 85 and older would have Alzheimer's by the midpoint of the century.

The Alzheimer's Association estimates that it costs $200 billion a year to care for Alzheimer's patients, with $140 billion of that paid by Medicare and Medicaid. By 2050, that bill will swell to more than $1 trillion a year, the group said.

The growth in cases will put pressure on generations behind them to provide massive amounts of care. Maria Carrillo, a scientist with the Alzheimer's Association in Chicago, said that baby boomers have "had a major impact on every system since they've been born."