The survey by the Center for Retirement Research at Boston College found that there is a large increase in the number of working Americans who likely won't be financially prepared to retire -- largely due to the escalating cost of healthcare.

The National Retirement Risk Index, released today by the Center for Retirement Research showed that 61 percent of today's workers will be at risk for not being financially prepared to retire -- a 17-point increase from the previous index in July 2007.

A 2007 study by the Employee Benefit Research Institute said that couples need to save about $300,000 in retirement to cover health expenses, assuming they live to average life expectancy and Medicare benefits remain at current levels.

"Medical expenses have increased 43 percent in the last five years and will likely increase at a higher rate compared to overall consumer spending," Paul Ballew of Nationwide, a Columbus insurance and financial services organization, said in a statement. "And, healthcare now accounts for more than 20 percent of all personal spending; double what it was in 1970."