Most new retirees like Medicare, and they give their coverage higher ratings than pre-retirees give commercial coverage.

But 44% of middle-income new retirees report that the monthly Medicare Part B premiums are higher than they had expected, according to analysts at the Center for a Secured Retirement.

The center is an arm of Bankers Life and Casualty Company, which is, in turn, a unit of CNO Financial Group Inc., Carmel, Ind. (NYSE:CNO).

The analysts recently published data on baby boomers’ thoughts about Medicare Part B premiums in a summary of results from a survey of 800 U.S. adults that was conducted in September 2011.

An independent research firm called people ages 47 to 75 who had annual household incomes of $25,000 to $75,000. The sample included 400 boomers who were not yet eligible for Medicare and 400 middle-income adults, ages 65 to 75, who are boomers or members of the Silent Generation and are eligible for Medicare.

Only about 43% of the new retirees said their health care expenses about what they had expected, and only 14% said their health care expenses are less than they had expected.

About 13% of the boomers who are not yet eligible for Medicare told survey workers that they think Medicare is free, and only 28% understand that Medicare enrollees pay a monthly premium, co-payment amounts and deductibles.

Most Medicare enrollees cover the cost of Medicare Part A hospitalization premiums with payments they or a spouse pay while they are of working age.

But most enrollees have to pay a separate monthly premiums for Medicare Part B, which covers physician services and outpatient services.

The monthly premium will be $99 this year, which is down from a high of $115.40 in 2011 but substantially higher than in 1998, when the premium was $43.80.

Only 22% understand that basic Medicare does not cover dental care, and just 18% understand that basic Medicare does not cover hearing care, the analysts say.