Yet health literacy can be particularly crucial for seniors. They’re usually coping with more complicated medical problems, including multiple chronic diseases, an array of drugs, a host of specialists. They have more instructions to decipher, more tests to schedule, more decisions to ponder.

Low health literacy makes those tasks more difficult, with troubling results. Studies indicate that people with low literacy have poorer health at higher cost. They’re less likely to take advantage of preventive tests and immunizations, and more apt to be hospitalized.

It may not help much that future cohorts of older adults will be better educated. “The demands of interacting with the health care system are increasing,” Dr. Wolff said. “Ask any adult child of a parent who’s been hospitalized. The system has gotten increasingly complex.”

That doesn’t mean patients deserve all the blame for misunderstandings and snafus. Rima Rudd, a longtime health literacy researcher at Harvard University, has persistently criticized the communications skills of health institutions and professionals.

“We give people findings and tell them about risk and expect people to make decisions based on those concepts, but we don’t explain them very well,” she said. “Are our forms readable? Are the directions after surgery written coherently? If it’s written in jargon, with confusing words and numbers, you won’t get the gist of it and you won’t get important information.”

A few years ago, Steven Rosen, 64, had spent more than two months at a Chicago hospital after several surgeries. Then a social worker came into his room and told his wife Dorothy, “You have to move him tomorrow to an L.T.A.C.”

“I don’t know what you’re talking about,” Ms. Rosen recalled saying. “What’s an L.T.A.C.?”

Question: Was she demonstrating inadequate health literacy, or should the social worker have clarified that L.T.A.C.s — long-term acute care hospitals — provide more care than nursing homes for very ill patients?