Once known for serving the poor, Medicaid now provides healthcare to one in six people in the Lower Hudson Valley at a cost to taxpayers of $2 billion a year. Today's Medicaid has taken on everyone from children to the elderly as it covers parts of the middle class in a region known for its affluence. It's also a program under assault from county, state and federal governments because of rising costs. New York's $53 billion price tag for Medicaid last year — the highest in the nation — is driven by aging baby boomers and those who need long-term care. The number of people on Medicaid has skyrocketed, partly because of the state's generous benefits. The demand has increased costs even as the state enacts major reforms. Statewide, 46,000 new people enrolled in Medicaid between April and July.