Decades after their university days, an increasing number of US seniors are still struggling to pay off student loan debt, according to a new report. 
And for some retirees, that means smaller Social Security checks -- sometimes the only funds elderly Americans live off when they leave the workforce.
For those aged 65 and older, the total amount of federal student debt ballooned more than six-fold from some $2.8 billion in 2005 to about $18.2 billion in 2013, says a Government Accountability Office report released last week.
That's a small fraction compared to the $1 trillion in total federal student loan debt held across all age groups. 
But it can still hit cash-strapped seniors hard since, according to the report, a cut of the borrower's Social Security disability, retirement, or survivor benefits can be claimed to pay off the loan in question.
The GAO found that, from 2002 to 2013, the number of people who saw their Social Security benefits offset to pay such debt rose about five-fold -- from some 31,000 to 155,000. 
In the 65 and older age group, that number grew from approximately 6,000 to about 36,000 during the same timeframe, representing roughly a 500 percent increase, it said.
While limits have been implemented on the amount that monthly benefits can be offset, "the value of the amount protected and retained by the borrower has fallen below the poverty threshold," the GAO found.
It warned that student loan debt held by seniors can be especially difficult to deal with "because, unlike other types of debt, it generally cannot be discharged in bankruptcy."
"Such debt can reduce net worth and income, thereby diminishing overall retirement financial security," the GAO said.
Still, only about three percent of households headed by those aged 65 or older have student loan debt. That compares to about 24 percent of households headed by those 64 or under.
In fact, older Americans are more likely to have other types of debt, the GAO said, noting for example that 29 percent of those aged 65 and over have home mortgage debt and 27 percent owe money from credit card use.