Alicia Chang, AP

Higher Medicare co-pays, sometimes just a few dollars more, led to fewer doctors visits and to more and longer hospital stays, a large new study reveals. With health care costs skyrocketing, many public and private insurers have required patients to pay more out-of-pocket when they seek care. The new study confirms what many policymakers had feared: cost-shifting moves can backfire.

“Patients may defer needed care and may wind up with a serious health event that might put them in the hospital. That's not good for the patients, not good for society, not good for anybody,” said Dr. Tim Carey, who heads the University of North Carolina's Sheps Center for Health Services Research.

The study, published in the New England Journal of Medicine, included nearly 900,000 seniors in 36 Medicare managed-care plans from 2001 to 2006. During that period, half of the plans raised co-pays for visits to doctors and specialists.

Researchers compared medical use patterns in those plans with use in similar Medicare managed-care plans that kept co-pays the same. Co-pays for prescription drugs remained unchanged in all plans. Among plans that increased patient cost-sharing, the average co-pay for a doctor visit roughly doubled, from $7.38 to $14.38. The co-pay to see a specialist jumped from $12.66 to $22.05. By contrast, the average co-pay for unchanged plans was $8.33 to see a doctor and $11.38 to see a specialist.

For every 100 people enrolled in plans that raised co-pays, there were 20 fewer doctor visits, 2 additional hospital admissions and 13 more days spent in the hospital in the year after the increase compared to those in plans whose co-pays did not change, researchers found.

The trend was most pronounced among blacks, people living in lower-income neighborhoods and those with chronic illnesses such as diabetes, high blood pressure or heart disease. The results suggest that raising co-pays to contain costs is counterproductive, said Dr. Amal Trivedi, assistant professor of community health at Brown University, who led the study. Not only may it lead to higher health care spending, but patients also suffer, he said.

The study was funded by grants from Pfizer, Inc. and the federal government.