Stock market losses have dampened the lifestyle of two-thirds of investors ages 50 to 70, with some saying they are postponing retirement or looking to go back to work, according to an AARP survey released yesterday.

Stock ownership among older investors had doubled in the past 10 years, with the result that some closest to retirement are now experiencing a "great deal of volatility when they want more certainty," said David Certner, AARP's federal affairs director.

Certner said the survey results show the need for pension reform and quality, independent investment advice for workers.

AARP in recent weeks surveyed 1,013 stock market investors between 50 and 70 years old.

Seventy-seven percent of those polled reported they lost money in the market in the past two years. Among those who suffered losses, 54 percent lost less than 25 percent in accounts that included stocks. One in four lost more than 25 percent but less than half their money. Nine percent lost more than half.

Among those retirees getting ready to head back into the work force is Jack Knox, 65, of Columbia, who retired five years ago as a manager of government contract policy with Northrop Grumman Corp.

His portfolio is down about one-third from the height of the bull market in 2000. He figures his retirement assets would be "getting pretty lean" in about 20 years, so he plans to go back to work, possibly as a real estate agent, to add to his savings.

Knox said he always planned on finding another paid position after leaving Northrop Grumman, but the bullish stock market had pushed up the value of his investments and instead he got busy with volunteer work.

"After opening my brokerage statement, I would say, 'Oh, my gosh,' " Knox said of his market gains. "Then the tide changed. I kept saying, 'Oh my gosh' on the other side."

He added, "I rode the bubble up and rode it down again. It's hard to complain. It had the feeling of being found money."

The majority of those polled by AARP held equities in individual retirement accounts and in an employer's 401(k) or 403(b) plan. Also, 44 percent owned individual stocks outside a retirement account.

Many workers, though, first became investors through a workplace retirement plan and some developed unrealistic expectations because of the bull market, Certner said.

"If there is any kind of silver lining, maybe people's expectations will become a little more realistic than they were five years ago," Certner said.

AARP's other findings from those who lost money:

Among those still working, one in five has postponed retirement because of market losses. Many who had anticipated retiring in their early 60s now expect to retire between 65 and 69.

Nearly 40 percent of those who lost money were retirees, and one-third of them have gone back to full- or part-time work.

Sixty-seven percent say market losses have changed their lifestyle. Nearly 60 percent are more carefully budgeting their money, 34 percent are taking fewer vacations and 30 percent have delayed a major purchase.

Forty-three percent said they would be less comfortable in retirement than they had anticipated.

Twenty percent expect in retirement to have trouble paying for health care and prescription drugs.

The telephone survey was conducted between Nov. 15 and Dec. 6 and has an error rate of plus or minus 3.5 percentage points.