Student debt can make it more challenging to prepare for retirement — and that is reflected in the retirement balances of older borrowers, Fidelity data shows. Retirement balances are roughly 30% lower among employees over age 50 who currently have student debt , at an average of $153,000, compared to $221,000 for savers in that age group who do not have such loans, the financial services company wrote in a report published Wednesday. Workers ages 18 to 49 with student loans have nest eggs