Americans may live significantly longer in the future than current U.S. government projections, and that could mean sharply higher costs than anticipated for Medicare and other programs, researchers reported on Monday.

The researchers say that by 2050 Americans may live as much as eight years longer than government forecasts and that spending by Medicare and Social Security could rise by $3.2 trillion to $8.3 trillion above current projections.

Advances in medical care will accelerate, stretching out lifespans, the MacArthur Research Network on an Aging Society wrote in the report, published in The Milbank Quarterly.

If we're right we've got a problem, Dr. Jack Rowe of Columbia University's School of Public Health and chairman of the MacArthur Research Network said in a telephone interview. Can we really afford to have everybody quit work at 65?

The research did not address any effects of longer lifespan on the current effort to overhaul the U.S. healthcare system.

U.S. government agencies' projections do not match the study's for increases in life expectancy because they assume improvements in mortality in the coming decades will decelerate, the researchers said.

The study projects that by 2050 life expectancy for women will rise to between 89.2 and 93.3 years and for men from 83.2 to 85.9 years.

The U.S. Census Bureau and the Social Security Administration project lower life expectancy in 2050 -- no more than 85.3 years for females and 80.9 years for males.

We don't know that we're right but we think rather than using these conservative estimates the nation is better served by having a range of estimates that include the potential for continued advances, Rowe said.

Rowe said there are other overlooked, but equally important implications that could arise from having an older and larger population than expected.

He said the work force, education system, the way cities are laid out and the retirement systems were not designed to support an aging society.