Dementia costs the United States $109 billion in direct care, according to a new study published by the New England Journal of Medicine. To put that in perspective, caring for heart disease costs about $102 billion and cancer $77 billion.

That's not even accounting for the unofficial costs of caring for a person with dementia, usually provided by family members, which would add an additional $50 billion to $106 billion to that number. Why is dementia care hitting our pockets so hard?

Without a way to prevent, cure or effectively treat these conditions yet, the bulk of the costs — 75 to 84 percent, the study found — involves helping patients in nursing homes or at home manage the most basic activities of life as they become increasingly impaired cognitively and then physically. [New York Times]

That equals annual costs of $41,000 to $56,000 per patient. As bad as the problem is now, it's only going to get worse as the baby boomer generation ages.

The study found that around 15 percent of people age 71 and older suffer from dementia, which includes Alzheimer's and other mental disorders. That adds up to about 3.8 million people who suffer from the disease, costing us around $215 billion. By 2040, the number will jump to 9.1 million people at a cost of $511 billion, according to the Times.

"The bottom line here is the same: Dementia is among the most costly diseases to society, and we need to address this if we're going to come to terms with the cost to the Medicare and Medicaid system," Matthew Baumgart, senior director of public policy at the Alzheimer's Association, told The Associated Press.

Not only do we have to fix our healthcare system, we also have to make progress on treating the disease, said study author Michael Hurd to Bloomberg Businessweek: "We need more research into interventions to delay or halt the onset of dementia, right now we don't really have anything at all."

The hope is that research initiatives, including the $100 million President Obama committed to mapping the human brain, will make some progress on a cure before the baby boomer generation overwhelms the system.