WASHINGTON — The expanding gap between rich and poor is not only widening the gulf in incomes and wealth in America. It is helping the rich lead longer lives, while cutting short the lives of those who are struggling, according to a study released this week by the Government Accountability Office.

Almost three-quarters of rich Americans who were in their 50s and 60s in 1992 were still alive in 2014. Just over half of poor Americans in their 50s and 60s in 1992 made it to 2014.

“It’s not only that rich people are living longer but some people’s life expectancy is actually shrinking compared to their parents, for some groups of people,” said Kathleen Romig, a senior policy analyst at the liberal Center on Budget and Policy Priorities.

Income inequality has roiled American society and politics for years, animating the rise of Barack Obama out of the collapse of the financial system in 2008, energizing right-wing populism and the emergence of nationalist leaders like Donald J. Trump, and pushing the Democratic Party leftward. Senator Bernie Sanders, a self-described democratic socialist who is seeking the Democratic presidential nomination, commissioned the report from the Government Accountability Office, Congress’s independent watchdog, and seized on its findings.