"Between the 1980s and 2000, life expectancy increases occurred nearly exclusively among high-education groups," the study said, giving some striking and convincing figures.
"Comparing 1981-88 with 1991-98, life expectancy at age 25 grew 1.4 years for high-education people but only 0.5 years for low-education people," the study said.
"Between 1990 and 2000, life expectancy grew 1.6 years for the high-education group but remained unchanged for the low-education group," it said.
The difference in longevity means you would have enough time to complete a bachelor's, master's and doctorate degree, the study showed.
"In 2000, life expectancy for a 25-year-old with a high school diploma or less was 50 years (to 75 years of age). For a person with a college education, life expectancy was nearly 57 years," the study showed.
Life expectancy grew across the board for all races and genders between 1990 and 2000.
But, at the same time, the longevity gap between the well-educated and poorly-educated widened.
"The 1980s and 1990s were periods of rapidly rising life expectancy, but the mortality declines that yielded these gains did not occur evenly by education group," the study says, trying to work out why.
After ruling out income disparities, the study focused on smoking and weight.
"The diseases contributing most to the growing education gap in mortality include diseases of the heart, lung and other cancers, and chronic obstructive pulmonary disease, all of which share tobacco use as a major risk factor," the study said.
"Beyond the differential change in smoking, there is the national trend toward increased obesity," it said.
"As with smoking, obesity is more common among the less-educated than among the better-educated. Further, recent research suggests that obesity might contribute to nearly as many deaths as tobacco does."
The researchers matched census population estimates to death certificate data covering 1990 to 2000, and cross-checked the data gathered with information in the National Longitudinal Mortality Study (NLMS).