Alzheimer's disease may affect as many as 4 million people and cost between $40 billion and $90 billion a year in diagnosis, care and lost income. Osteoporosis, loss of bone mass resulting in debilitating hip fractures and bone breaks, has been estimated to cost $20 billion a year.

Such figures are only samples of what will be involved in the struggle to control national health care costs.

They do not count the human suffering and potential for even greater outlays since the number of people living past 85 is rising rapidly. Within the next half-century, the number of Alzheimer's patients is expected to reach up to 14 million people, according to the Senate Labor and Human Resources Committee.

And the number of hip fractures, now about 220,000, could rise to 840,000, according to one estimate.

With these numbers in mind, Congress, spurred by the government's National Institute on Aging (NIA) and the nonprofit Alliance for Aging Research, has enacted legislation to boost research on diseases of the aging.

In related appropriations action, the NIA has been given an additional $85.3 million to bring its funding to $325 million in fiscal 1991, by far the largest percentage increase for any of the National Institutes of Health.

Part of the money will go for new research, part for existing projects and part to finance 10 "Claude D. Pepper Older Americans Independence Centers," named for the late House Rules Committee chairman who was a tireless advocate of better health care and research for the elderly.

The centers not only will conduct but also train professionals in problems of the aging, develop methods of care and work on methods to promote the independence of the aging.

"With the skyrocketing cost of health care for the elderly and the rapidly growing number of older Americans, this legislation is expected to help stave off financial ruin of both our public health system and family pocketbooks," said the Senate labor committee report on the bill, which was signed by the president.

One particularly promising line of inquiry, endorsed by Sen. Tom Harkin (D-Iowa), one of the bill's principal sponsors, is drug therapy for Alzheimer's.

Paul DelPonte, spokesman for the Alliance for Aging Research, which is headed by John L. Steffens of Merrill-Lynch Consumer Markets, with former NIA director Robert N. Butler as vice chairman, said, "We expect within a year or two to have simple therapeutic tests that would diagnose Alzheimer's early, in the one to three-year period before the disease becomes highly noticeable.

"That could save Medicare alone $1 billion annually in diagnostic costs, because now, when people are concerned they have it, they go for repeated tests before it can be established whether they have it."

Edward L. Schneider, of the University of Southern California's Andrus Gerontology Center, predicted earlier this year that within a decade new drugs could be developed to delay the onset of the serious, debilitating stages of Alzheimer's disease by up to five years.

Such a development, precisely the kind of thing the bill is designed to foster, eventually could save billions of dollars by permitting people who have the disease to live relatively normally for years longer than now possible. The average years -- and costs -- of care required for Alzheimer's victims would be shortened substantially.

Since research is always chancey, spending more money on it provides no guarantees. But Harkin does not think so. He told the Senate when the bill passed that, from the point of view of improving people's lives as well as saving money on future costs of care, every dollar put into Alzheimer's and similar research on aging is "a blue chip investment."