It is early morning, and Lorraine Phifer is gently kneading the toes of her 47-year-old son, Billy. Cerebral palsy, which has left Billy's body helpless, sometimes causes his toes to curl, and Phifer must straighten them before putting on his socks and shoes.

After pushing and pulling him into his clothes, she spoons him thickened apple juice containing the first of about three dozen pills he must take every day for myriad health problems that in recent years have included reflux so severe he vomits blood.

Phifer is not complaining. She understands this is the life she accepted when she refused long ago to give up her son to some institution. Besides, she loves Billy. When he smiles, she smiles; when he puckers his lips, she laughs.

But Phifer is 74. After years of kneeling over the tub to bathe her son, her knees are shot. And hernia surgery last year only underlined what she already knew: Her 147-pound son is too heavy for her to move by herself.

"I know I have to take care of him as long as I can," she said. "I wonder who would take over."

Phifer is part of a large and growing population of aging Americans closing in on the end of their ability to care for their children with developmental disabilities.

Experts say government agencies and programs will be overwhelmed by a demand for services as these parents die or simply cannot care for their grown children anymore.

"It's a nightmare waiting to happen," said Matt Toohey, executive director of Access Services of Northern Illinois, a nonprofit organization that assists people with developmental disabilities and their families.

Phifer's household is one of an estimated 707,000 in the United States in which parents 60 and older are caring for children with developmental disabilities. Right behind them doing the same are 977,000 households in which parents are between the ages of 41 and 59.

Experts say states around the country are unprepared to help families when they start asking for it. They say the waiting lists for publicly funded services such as residential care facilities -- an estimated 58,000 families are on the lists now -- do not begin to reflect the need that is out there, or soon will be.

In Illinois, for example, no waiting list is kept. But while there are an estimated 29,000 caregivers older than 60, Toohey said there are 500 vacancies in residential care facilities in the entire state.

What makes some of the numbers more troubling is that nobody knows if they are accurate.

"Some people say as many as 40, 50 percent [of these households] we don't even know about," said Tamar Heller, who heads the University of Illinois at Chicago's Department of Disability and Human Development.

The biggest reason is these people have never asked for help. "They may have backed away from government services because they were afraid if they got the services the child would be taken from them," said Lisa Eden, program manager with the Illinois Department on Aging.

But ultimately many will be forced to ask for help, in large part because unlike previous generations, these parents cannot count on outliving their children, a result of advances in medicine and technology.

For example, the life expectancy for someone with Down syndrome has increased dramatically, from just nine years in the 1920s to 56 years today.

The outlook was bleak when Luella Jones's daughter, now 52, was born with Down syndrome and heart problems. "We were told she would not live, and they encouraged us the leave her in the hospital," Jones said.

Today, these children live long enough to develop serious health problems of their own.

For reasons that are not entirely understood, people with Down syndrome have higher risk than the general public of developing Alzheimer's disease. Jones said her daughter was diagnosed with Alzheimer's four years ago.

Phifer said Billy has in recent years been hit with a host of medical problems. "My son is a poster child for everything that can go wrong if you're aging with cerebral palsy," she said.

Once parents start asking public agencies for help, it could add up to a staggering amount of money.

"Oftentimes we see an aging mother taking care of a son or daughter on their own Social Security [and] they don't even know their son or daughter are eligible for their own Social Security," said Daniel Scarborough, a project director with The ARC of the United States, a Maryland-based nonprofit organization for developmental, intellectual and cognitive disabilities.

Supplemental security income becomes available at age 18, noted DiAnn Baxley, director of project training and research at the University of Albany's Center on Intellectual Disabilities.

Nor is it clear where developmentally disabled adults might live when their parents can no longer provide care at home. The facilities available are often understaffed because of low pay, Baxley said.

Among the few places that might be available are nursing homes, though those may not be equipped to meet the needs of these patients, Heller said. Besides, federal law prohibits putting people younger than 60 with developmental disabilities in nursing homes unless they require skilled nursing care.

"They just can't be dumped there," Heller said.

Increasing funding for programs that help elderly caregivers is a possibility, but those who work with these people are not holding their breath.

"In Illinois, we've got a $1.7 billion deficit," said Toohey. "Where are we going to get it [more funding]?"

Myra Schmitt of Rockford, Ill., has been unable to find a group home for her 39-year-old autistic son, and says she has been told there is not any money to build more. At the same time, she reads in the paper that a local museum recently received about $1 million from the federal government to build an exhibit hall for a dinosaur.

"They just got a $990,000 grant to display a dead animal, and I have a live son," said Schmitt, 68.

There are some efforts around the country to help senior caregivers.

In Illinois, Eden is heading a pilot project that will help elderly caregivers get services and plan for when they can no longer care for family members. It is funded by the U.S. Department of Health and Human Services' Administration on Aging, in collaboration with Heller's department.

Similar programs covering more than 30 states are being developed by the Administration on Aging and The ARC.

One of those benefiting is Phifer. Her son now rides in a $4,000 wheelchair paid for by Medicaid. Her home is equipped with a device that allows her to lift her son from his bed and place him in his wheelchair or the bathtub with a push of a button -- paid for by the state's Department of Human Services.

Still she worries. And she hopes her son dies before she does.

"The only time things are good for these children," said Phifer, "is if they [their parents] are there all the time and supervise everything."

Prescription drugs line a kitchen shelf as Lorraine Phifer, 74, feeds her son Billy breakfast at their Chicago home.