At the end of the recession, in late February 2009, a survey found 25 percent of adult respondents to a survey indicated they were "not too" or "not at all" confident their financial position would see them through retirement, the think-tank said.
In the latest survey, 38 percent indicated they were concerned they could not fund their retirement with confidence.
The center said there was "a major shift in the pattern," in that those most concerned about retirement are younger and middle aged workers. In 2009, by contrast, it was the "Gloomy Boomers," adults in their mid-50s, who were most concerned about nest eggs that were too small.
In the more recent survey, "worries peak among adults in their late 30s -- many of whom are the older sons and daughters of the Baby Boom generation," the study found.
In that age bracket, those between the ages of 36 and 40, a survey-topping 53 percent indicated they were sure their retirement could be properly financed.
The survey was conducted July 16-26 and involved 1,505 interviews. The results have a margin of sampling error of plus or minus 2.8 percentage points, the center said.