Impact of HMO withdrawals on vulnerable Medicare beneficiaries.

The Medicare+Choice (M+C) program has faced successive waves of plan withdrawals since 1999. We collected data from 1,055 beneficiaries who were involuntarily disenrolled from a health maintenance organization (HMO) that withdrew from six large markets in 1999 to investigate how they were impacted by the forced change in coverage. Administrative data from this HMO were used to oversample beneficiaries who were perceived to be vulnerable based on their poor health status in the period before the HMO withdrawal. Although most beneficiaries dealt with the withdrawals without major problems, appreciable numbers of beneficiaries did report adverse impacts. These negative impacts were more likely to occur for low-education, low-income, minority beneficiaries. We found little evidence, however, that beneficiaries who were vulnerable due to their poorer health experienced more adverse effects.