Dementia costs more each year in the United States than cancer or heart disease, with annual costs ranging from $157 billion to $215 billion, according to a study released Wednesday.

Much of the costs come from long-term care giving, and the price tag is expected to more than double by 2040, said the study by the non-profit RAND Corporation in the April 4 edition of the New England Journal of Medicine.

"The economic burden of caring for people in the United States with dementia is large and growing larger," said Michael Hurd, the study's lead author and a senior economist at RAND.

"Our findings underscore the urgency of recent federal efforts to develop a coordinated plan to address the growing impact of dementia on American society."

Some 5.3 million Americans currently suffer from Alzheimer's disease, the most common form of dementia, according to the Centers for Disease Control and Prevention.

By 2050, the number of people with Alzheimer's is expected to more than double because of the aging population, the CDC has said.

President Barack Obama signed into law the National Alzheimer's Project Act in 2011, which aims in part to track the costs of dementia for government and society.

Dementia affects about 15 percent of people over 70 and is estimated to cost society between $41,000 and $56,000 per person every year, the New England Journal of Medicine study said.

"Our calculations suggest that the aging of the US population will result in an increase of nearly 80 percent in total societal costs per adult by 2040," it said.

"Our estimate places dementia among the diseases that are the most costly to society."

When researchers considered just direct health care expenditures, and not the cost of informal care, dementia cost about $109 billion per year compared to $102 billion in 2010 for heart disease. Cancer costs about $77 billion.

Informal care for patients with dementia drives the cost even higher, experts said.

"Much of the expense is informal care and out of pocket expenses," said Mary Sano, director of the Alzheimer Disease Research Center at Mount Sinai Medical Center in New York.

Government assistance in the form of Medicare pays only about 10 percent of the costs per year, added Sano, who was not involved with the study.

"Out of pocket or replacement care is the major burden born by families of those with dementia."

The RAND study's estimate of total cost was lower than the Alzheimer's Association's recent estimate of $172 billion in 2010 dollars, likely due to a higher population prevalence given by the AA and a failure to adjust for the cost of co-existing conditions, the article said.