A ghost's Horrifying Visage can age a creature as follows:
Horrifying Visage: Each non-undead creature within 60 feet of the ghost that can see it must succeed on a DC 13 Wisdom saving throw or
be frightened for 1 minute. If the save fails by 5 or more, the
target also ages 1d4 x 10 years. A frightened target can repeat the
saving throw at the end of each of its turns, ending the frightened
condition on itself on a success. If a target's saving throw is
successful or the effect ends for it, the target is immune to this
ghost's Horrifying Visage for the next 24 hours. The aging effect can
be reversed with a greater restoration spell, but only within 24 hours
of it occurring.
What's unclear is whether this can be fatal or if the effects are purely cosmetic. For elves, this is likely not an issue, but does a human simply go from a healthy young adult, to an elder who likely works out very regularly because there is no stat adjustments for age (that I know of)?