Recently, the Consumer Financial Protection Bureau (CFPB) concluded that Americans who are 60 or older represent the fastest-growing segment of student-loan borrowers.

In fact, between 2005 and 2015, their numbers quadrupled to nearly 3 million.

Not surprisingly, the majority of those loans were for the borrowers' children or grandchildren. Sounds nice? As understandable as this familial generosity may be, some observers caution that it really isn't so good for those parents' and grandparents' financial security, especially as they enter retirement.

"This is not a good trend," said Paul Lightfoot, president of Optima Asset Management in Dallas. "For a generation already identified with not having put aside enough for retirement, those over 60 can quickly deplete and/or jeopardize their retirement savings when co-signing for student loans."

The key problem, of course, is that cosigners are legally responsible for covering the debt if the student defaults. Many senior citizens are on a fixed budget, so that debt could hit them hard. "At a time in their lives when medical expenses begin to rise, seniors might find themselves forgoing necessary prescriptions or doctor’s appointments in order to repay the student loan," said Lightfoot.

A cosigner is supposed to strengthen a student's chances of securing a loan, or even of securing a lower rate. While that's often true, older Americans' financial resources shouldn't be overestimated. The CFPB report also found that, as of 2015, 37 percent of the federal student loan borrowers who were 65 or older were in default -- 20 percentage points higher than the default rate for borrowers 49 and under.

Moreover, many of those older borrowers lost some Social Security benefits because of unpaid student loans: 40,000 borrowers in 2015, a rise of some 360 percent over the preceding 10 years.

Lightfoot further points out that there's no guarantee the borrowed money will go for the intended purpose. "While private student loans are intended to cover the costs associated with gaining a college education, there is little to prevent the student from spending the money on items other than college-related expenses," Lightfoot warned.

The fact is, even the best intentions can go awry. If the student misses just one payment, that could damage the grandparent's credit rating. "The cosigner will be held liable," said Michelle Herd, a senior client advisor at TFC Financial Management, in Boston.

Things could get especially complicated if the cosigning grandparent becomes disabled or dies before the loan is paid off. Some loans require full repayment at the death of a cosigner. "It’s important to fully understand the implications for the loan under various scenarios," she said.

Beyond the financial complications, cosigning for a child or grandchild can bring up uncomfortable relationship issues. One grandchild might feel slighted, for instance, if another receives what's perceived to be disproportionate financial assistance. Such arrangements "can lead to conflict," commented Gary Schwartz, an advisor at Madison Planning, in West Harrison, N.Y. "In family finances, equal and fair are often not the same."

But of course, it is precisely this sort of strong emotion that often leads to offers of cosigning. “This is an unusual maneuver that’s likely triggered by emotions or family dynamics," observed Brian Mercado, a certified financial planner at JSF Financial, in Los Angeles. "Financial decisions based on emotions are usually not advisable."

However well intended, there may be better alternatives. Instead of cosigning a loan, advisors suggest a number of other ways to help with educational expenses. “I’d rather a client open a 529 plan," said Schwartz, at Madison Planning, referring to the tax-advantaged, state-sponsored college-savings accounts. "In addition to the regular benefits, when a 529 plan is in a grandparent’s name [as opposed to the student's] it is usually not included by schools when determining financial aid."

Other ideas include opening a Coverdell Education Savings Account, which is similar to a 529 but with a contribution cap (the current limit is $2,000 per student), or pay tuition expenses directly to the school. Such educational gifts are exempt from gift-tax calculations.

Speaking of gift tax, a philanthropic grandparent could always assist a needy relative with a direct donation. "One option is to gift money to the grandchild each year, up to the IRS annual exclusion amount, without any gift tax implications," said Herd, at TFC Financial. In 2018, the annual exclusion limit is $15,000 per recipient.