A new look at how the U.S. middle class thinks about retirement reveals surprising views about how long they expect to live and work.

About half of middle-income Americans currently working plan to work beyond age 65, according to a study by the Transamerica Center for Retirement Studies and the Transamerica Institute. Many say this is their desire, but about 8 in 10 also cite financial challenges, including a lack of savings and concerns that Social Security does not provide enough financial support.

Transamerica defines the “middle class” – a broad sociological term rather than a strict financial measure of income – as people earning between $50,000 and $200,000 annually, which is about 55 percent of U.S. adults.

“Many are saving for retirement, but the question is whether they are saving enough,” Catherine Collinson, CEO of the Transamerica Institute, told CBS MoneyWatch.

The dangers of a longer life

Middle-class households have an average of $66,000 saved in their retirement accounts, she noted, citing the survey data. But the more money saved, the more likely it is that that nest egg will not be enough to fund retirement, given a person’s current age and lifestyle. It is also far from the 1.5 million US dollars that the average worker says he or she has to pay for a comfortable retirement, according to a study published earlier this year by Northwestern Mutual.

Certainly, the number of 401(k) millionaires – people with at least a million dollars in their retirement accounts – has recently reached a new recordthanks to gains on the stock market, as new data from Fidelity shows. But that only reflects about 500,000 accounts, a fraction of the roughly 160 million people in the U.S. labor market.

Meanwhile, many middle-class workers expect their retirement to last 25 years or more, as they expect to live to an average age of 90. But a longer retirement requires more savings to afford more years out of the workforce.

“Longer life spans are causing people to rethink their life path, including their time in the workforce relative to retirement,” Collinson added. “Many envision working longer and retiring at an older age, giving them more time to earn and save money, while others plan to fund a longer retirement.”

“No real retirement”

In the United States, it is becoming increasingly common for people over 65 to work. According to the Pew Research Center, about one in five people over this age – or about 11 million Americans – are still employed.

Some, like Larry and Joyce Gesick, who are 77 and 66 years old respectively, have recently told According to CBS News, they continue to work for financial reasons. “It’s not really retirement,” Joyce told CBS News. “It’s work every day.”

Only about 10% of Americans between the ages of 62 and 70 are retired and financially secure. That’s the view of well-known retirement expert Teresa Ghilarducci. Her book, “Work, Retire, Repeat: The Uncertainty of Retirement in the New Economy,” examines the financial pressures facing an increasing number of Americans in retirement.

The reason for this lies in part in the current retirement system, says Ghilarducci, which puts the responsibility on workers to make their own savings decisions through their 401(k) and similar plans.

In an ideal world, these plans can work well for retirement planning. But, as Ghilarducci CBS MoneyWatch said earlier this year, It is common for employees to lose their jobs or experience financial difficulties, thwarting their best intentions to save money for retirement.

Even middle-class workers with access to 401(k) plans don’t always participate. The Transamerica study found that about one in seven doesn’t use employer-sponsored plans.

And once workers have a 401(k) plan, many use the savings as a financial cushion before retirement, the analysis found. About a third said they had tapped their 401(k) or other retirement plan for a loan, early withdrawal or emergency withdrawal, a rate Transamerica called “worrying.” The top reasons for doing so were financial hardship or paying off debt, according to the company.

Such withdrawals can reduce the ability to save for a financially comfortable retirement and increase the risk of running out of money in old age.

Despite these challenges, about seven in 10 middle-class Americans told Transamerica they are confident they can live a comfortable lifestyle in retirement. Many envision traveling, volunteering or caring for grandchildren after they retire.

“The middle class has an optimistic view of retirement as a time in life that offers opportunities for travel, time with family and friends, hobbies and more,” Collinson noted. “However, contrary to long-standing ideas, the middle class does not see retirement and work as mutually exclusive.”