A new study finds that Alzheimer’s is the most expensive malady in the U.S., costing families and society $157 billion to $215 billion a year.

The study — by the nonprofit RAND Corp., estimates that around 4.1 million Americans suffer from dementia. That’s less than the widely cited 5.2 million estimate from the Alzheimer’s Association, which comes from a study that included people with less severe impairment.

The biggest cost of Alzheimer’s and other types of dementia isn’t drugs or other medical treatments, but the care that’s needed just to get mentally impaired people through daily life.

Dementia’s direct costs, from medicines to nursing homes, are $109 billion a year in 2010 dollars. That compares to $102 billion for heart disease and $77 billion for cancer.

The study was sponsored by the government’s National Institute on Aging and will be published in Thursday’s New England Journal of Medicine.