“GROWING OLD IN AMERICA,” 8 p.m. Saturday...

“GROWING OLD IN AMERICA,” 8 p.m. Saturday (7) (3) (10) (42)--America’s aged population may be growing, but the network documentary is shrinking.

The ABC News Closeup unit--which has given America some superlative three-hour documentaries in recent years--has been reduced and restructured for budgetary reasons. So there’s no telling what lies beyond this three-hour ABC program that will explore the process of aging in America.

There are many subjects--aging is one of them--that can’t be given justice in an hour or the 20-minute segments in magazine shows. So ABC deserves credit for not only expanding the form, but also for bringing style to long documentaries without sacrificing significance.

Hence the longer “Growing Old in America” is welcome indeed. It will focus on the range of long-term care of the elderly, and look at whether their health care needs are being met both in terms of costs and quality. What are the futures of Medicare? Medicaid?

Incredibly, America’s 85-plus group is expected to double in 15 years. That’s a happy development to be sure, but one that also causes new concerns and raises new questions about the responsibility for health care. Who should be responsible for elderly care? The ABC program examines that question while also discussing new burdens being placed on families of elderly persons and speculating about the future of baby boomers.

The principal writer for all the Closeup programs is Marshall Frady, a former print reporter whose writing, research and reporting skills are rare among TV journalists. Frady also was to have done at least a portion of the on-camera narration, as he has in other Closeup documentaries. However, he was bumped in favor of Hugh Downs of “20/20,” as ABC tries to give wider exposure to its anchormen.

And what chance has ABC Closeup of reaching old age in its present form? Less than ever, it seems, but stay tuned.