It has been a central campaign promise from Mitt Romney: His Medicare overhaul plan would not touch benefits for anyone older than 55.

That may not, however, be the case with the Republican presidential nominee’s other health-care proposals. A growing body of research suggests that his plans to repeal the Affordable Care Act and cut Medicaid funding would have a direct impact on the health care that seniors receive.

Repealing the health law would mean higher Medicare premiums, the Kaiser Family Foundation found in a recent analysis. Wellness visits and prescription drugs also would cost more. Although under the current law, reductions in doctor payments could create an access issue.

The impact could be greatest for the lowest-income seniors, who qualify for both the Medicare and Medicaid programs, and there could be a significant slowdown in federal funds available for their care.

The health-care law cuts $716 billion in Medicare spending, largely by reducing how much insurers and health-care providers get paid to manage seniors’ care. Since Medicare beneficiaries pay a percentage of the program’s overall budget, lower spending means lower premiums.

“If the Medicare savings are repealed, and the benefit enhancements are repealed, there’s a direct effect on seniors today,” said Tricia Neuman, director of the Kaiser Family Foundation’s Medicare Policy Project.

“An expected slower rate of growth in Medicare spending leads to a slower rate of growth in beneficiary out-of-pocket payments,” the February 2012 research brief concluded.