If you can walk a quarter-mile, odds are you have at least six years of life left in you, scientists announced today.

And the faster you can do it, the longer you might live.

While walking is no guarantee of health or longevity, a new study found that the ability of elderly people to do the quarter-mile was an "important determinant" in whether they'd be alive six years later and how much illness and disability they would endure.

"The ability to complete this walk was a powerful predictor of health outcomes," said study leader Anne Newman of the University of Pittsburgh School of Medicine. "In fact, we found that the people who could not complete the walk were at an extremely high risk of later disability and death."

Newman and colleagues recruited nearly 2,700 white and African-American men and women aged 70 to 79 to complete in non-running races. All the participants were screened and determined to be in relatively good health, and they had all said they had previously walked that far with no problem.

However, only 86 percent of them finished.

The scientists then monitored the health and mortality of all participants for the next six years.

"There was a big gap in health outcomes between people who could complete the longer walk and people who could not, with the latter being at an extremely high risk of becoming disabled or dying," Newman said. "What was really surprising is that these people were not aware of how limited they actually were."

Finishing times were found to be crucial, too. Those who completed the walk but were among the slowest 25 percent faced three times greater risk of death than the speedier folks.

The study is detailed today in the Journal of the American Medical Association.