The large number of complex insurance choices offered by Medicare Advantage programs may overwhelm many U.S. seniors, researchers say.J. Michael McWilliams of the Harvard Medical School, a practicing general internist at Brigham and Women\'s Hospital, says the Medicare Modernization Act of 2003 initiated a series of payment increases to the Medicare Advantage program.The payment hikes dramatically increased the number of private plans participating in the program and encouraged plans to compete for enrollees by offering lower premiums and more generous benefits, such as prescription drug coverage.McWilliams and colleagues looked at 21,815 enrollment decisions from 2004 to 2007 made by 6,672 participants in a national longitudinal survey.The study, published in the journal Health Affairs, found on average an increase in the number of plans was associated with increased Medicare Advantage enrollment if the number of available plan options was fewer than 15. However, if the number of options surpassed 30, such increases were associated with decreased enrollment, the study found.More importantly, beneficiaries with low cognitive function were substantially less likely than their peers with high cognitive function to appreciate the advantages offered by these plans -- choosing to remain in the traditional Medicare program instead, McWilliams says.