WASHINGTON (CBS/AP) – Far more people than previously thought are providing billions of hours of unpaid care to Alzheimer’s patients.

A report released by the Alzheimer’s Association says nearly 15 million caregivers provide unpaid care to people with dementia. The caregivers are mostly family and friends.

READ MORE: San Jose Arts Committee Votes to Remove Controversial Statue of Thomas Fallon

The fact that it takes so many more people to care for these patients reflects the burden of an illness that not only robs people of the ability to do the simplest activities — but that patients can survive in an increasingly incapacitated state for up to a decade or two.

Dr. William Thies of the Alzheimer’s Association says caring for someone with Alzheimer’s is “too much of a job for any one person.” He says, “Even Superman can’t do it.”

READ MORE: Multiple Earthquakes Rattle Sierra Nevada Near Truckee Thursday Night

The study says a decade ago about 10 million caregivers were estimated to provide 8.5 billion hours of unpaid care for Alzheimer’s patients. Now it’s about 17 billion hours of unpaid care, valued at more than $202 billion.

An estimated 5.4 million Americans have the mind-destroying disease.

MORE NEWS: Pandemic Weight Problems, Eating Disorders Affect Children

(Copyright 2011 by CBS San Francisco. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. Wire services may have contributed to this report.)