It's easy to think of student debt as a younger person's problem. But Americans aged 50 and over actually account for about 22% of outstanding student loan debt in the U.S., says AARP.

And it's easy to see why older Americans wind up saddled with debt. Many extend their student loan payments or refinance their loans repeatedly in an effort to shrink their monthly payments, all the while sentencing themselves to years and years of having that debt hang over their heads.

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Now, if you're going to pursue a degree, some amount of student loan debt may be unavoidable. But do be careful in the course of committing to student loans. If you borrow too much money, it could easily end up putting your retirement at risk.

The danger of student loan debt

Any debt you sign up for will end up monopolizing a chunk of your income for a period of time. That's a given. But if you take on too much student loan debt, you might struggle to keep up with your payments. From there, you might do everything you can to lower your monthly payments to keep them affordable.

But when you extend your loan repayment period to lower your monthly payments, you inevitably end up spending more money on student loan interest. That's money that could be going into a retirement savings plan instead.

Along these lines, you may not be able to swing student loan payments and retirement plan contributions simultaneously. But if it takes you 20, 25, or 30 years to pay off your student loans, that means you may not end up beginning to save for retirement until your 50s. At that point, you may only have around a decade and change to build a nest egg, which could leave you with a whopping financial shortfall on your hands.

That's why you really need to be careful when committing to student loans. Not only should you aim to keep your debt as low as possible, but you should also aim to take out loans that will be repayable in roughly 10 years. That's the standard repayment period for federal student loans, and it might leave you student debt-free by your early 30s.

Even if you have to delay retirement savings until then, that conceivably gives you a 35-year window or more to contribute to an IRA or 401(k). And that's far better than first beginning to save for retirement in your 50s.

Of course, given the cost of college today, keeping your student debt to a minimum is easier said than done. But choosing your school wisely could help keep your costs -- and debt -- down.

Meanwhile, if you've recently graduated from college and now coming to terms with repaying your student loans, resist the urge to extend your repayment window. It may be tempting to set yourself up with lower monthly payments while you're young and first embarking on a career. But the sooner your student loans are done with, the sooner you can start focusing on retirement savings. And that's an important thing.