A comprehensive Government Accountability Office study commissioned by Sen. Bernie Sanders and published Monday found that low-income Americans have significantly shorter lives than the rich, leading the Vermont senator to declare that poverty in the world's wealthiest nation is a "death sentence."

"Poverty is a life-threatening issue for millions of people in this country, and this report confirms it," Sanders, a 2020 Democratic presidential candidate, said in a statement. "We are in a crisis never before seen in a rich, industrialized democracy."

"Poverty is a life-threatening issue for millions of people in this country, and this report confirms it."

—Sen. Bernie Sanders

To determine the relationship between wealth—or lack thereof—and life expectancy, the GAO examined a representative sample of Americans born from 1931 through 1941, making them between 51 and 61 years of age in 1992.

"The same individuals have been re-interviewed every two years since, provided they continued to participate in the survey, and the most recent complete data is from 2014, when those who were still alive were 73 to 83 years old," according to the GAO.

The agency found that just 48 percent of those in the bottom 20 percent of the wealth distribution were still alive in 2014. By contrast, over 75 percent of those in the wealthiest 20 percent were still alive, indicating that—in the words of the GAO—"income and wealth each have strong associations with longevity."

"For three straight years, overall life expectancy in the wealthiest nation in world history has been declining, often driven by deaths of desperation and despair: liver disease, drug overdoses, and suicide," Sanders noted.

The Vermont senator stressed that only immediate and transformative action will be enough to close the growing and deadly gap between the rich and poor.

According to the GAO, the average wealth of the richest 20 percent of older U.S. households more than doubled between 1989 and 2016. Meanwhile, between 1989 and 2013, the average wealth of older households in the bottom 20 percent fell from $4,500 to negative $4,300.

"We must put an end to the obscene income and wealth inequality in our country, and ensure living wages, quality healthcare, and retirement security for our seniors as human rights," sand Sanders. "If we do not urgently act to solve the economic distress of millions of Americans, a whole generation will be condemned to early death."