Feb. 1--Former office assistant Dorothy Rinehart had no intention of leaving the workforce permanently when she took early retirement to care for her ailing mother.

Like a lot of her peers, Rinehart, 69, isn't in a position to retire. A single mother of four, she didn't have much left over after expenses to invest in a 401(k) in her younger years.

"I wish, now, I'd done things differently," she said. "But the reality is, after my mother passed, I had to go back to work." Rinehart is among a growing number of seniors who have either delayed retirement or are returning to the workforce after years away.

Even before the recession, many older Americans had to work. About 40 percent of baby boomers have no assets, according to the Employee Benefit Research Institute.

Advances in medicine are partly to blame.

"People are living longer, and a lot of them are outliving their savings," said Carleen MacKay, workforce policy advisor for the American Association of Retired Persons.

In spite of the organization's name, by the way, more than half of AARP members hold full- or part-time jobs.

RECESSION MADE IT WORSE

A national foreclosure epidemic cost many older people their houses or reduced value for home equity lines or reverse mortgages.

At the same time, nest eggs that cared for previous generations are less reliable.

Only 18 percent of seniors in the private sector have a pension plan, according to AARP. And if the government takes over a troubled company's pensions, pension holder pay decreases.

The transition to 401(k) and Individual Retirement Accounts has made seniors more vulnerable to stock market volatility.

Barbara Bert, 66, blames the economy for her recent decision to return to work after retiring in 2007 from a job servicing student loans. She's now a cook at the Bakersfield Senior Center.

"The economy is something else," she said. "I don't see how people survive. I've never seen it like this in all my days."

CHALLENGES SENIORS FACE

Seniors should consult a tax advisor and the Social Security Administration before leaving retirement.

Depending on your age and how much you earn, Social Security benefits might be reduced.

Those who do go back to work, or who work longer, face a tough job market.

The nation isn't quite at the unemployment levels of the 1930s, when a quarter of the country was out of work. But Kern County's unemployment rate in December was 11.8 percent, according to the California Employment Development Department.