MONDAY, March 9 (HealthDay News) -- More than three-quarters of adult Americans who have health insurance say they still worry about paying more for their medical care, and nearly 50 percent say they're "very" or "extremely" worried about the issue, a new Harris Interactive/HealthDay poll shows.

More than half (57 percent) of those polled said they feared losing their health insurance sometime in the future, which may explain another key finding in the poll -- sizeable numbers of Americans said they're skipping doctor visits or not getting prescriptions filled to save money.

Middle-aged Americans -- people too old to be blasé about their health but too young to be covered by Medicare -- seemed most worried about paying their health care bills. Among insured individuals aged 45 to 64, a full 84 percent said they were concerned that rising health care costs would exceed their ability to pay.

Only 8 percent of all insured Americans polled were "not at all worried" about getting health care coverage.

"Many are, in fact, not filling prescriptions, skipping a doctor's visit, not following up on something that was recommended by the doctor, taking a medication less or pill-splitting, doing without dental care," said Humphrey Taylor, chairman of The Harris Poll.

He added that with the economy in a tailspin and many Americans losing their employer-based health insurance, the problem may only get worse. "If the number of uninsured rises sharply, one would expect to see these numbers increase," Taylor said.

One consumer advocate wasn't surprised by the results of the poll, which included 2,078 adults surveyed between Feb. 25 and 27.

"Even for people who have insurance, increasingly, the costs have been shifted to them -- and those costs have risen," said Carol Pryor, policy director at The Access Project, a nonprofit group dedicated to making health care available to more Americans. More and more, she added, insured Americans are paying higher deductibles and co-pays, stretching their ability to get proper medical care.

Pryor agreed with Taylor that the situation is only likely to get worse, since "more people are becoming uninsured as a result of the economic meltdown."