There are several spells which can reverse the aging effects or prevent them.
Reverse Lifeline, the reverse form of the 8th level spell wizard spell Accelerate Lifeline. Quoted from Wizard’s Spell Compendium.
The reverse of this spell, reverse lifeline, cannot bring back the
dead, but it can reduce the age of the recipient by up to one year per
level of the caster.
And the 7th level wizard spell Younger.
This obscure and dangerous spell makes the recipient up to one year
younger per level of the caster (one year minimum), as decided by the
caster. It can be cast only upon a willing recipient, negating the
penalties of advancing age, and restoring a youthful appearance. It
will not make a creature younger than a young adult.
In addition to the 9th level wizard spell Vampiric Youthfulness, 8th level wizard spell Protection From Time and 6th level priest spell Age Creature.
If you are willing to look at items that could serve your purpose there is the Elixir of Youth, quoted from the Encyclopedia Magica
Quaffing this rare and potent elixir reverses aging. Taking the full
potion at once reduces the imbiber's age by 1d4+1 years. Taking just a
sip first, instead of drinking it down, reduces the potency of the
liquid, and drinking the lower potency liquid reduces age by only 1d3
Or the Amulet of Perpetual Youth
This amulet glows with a faint, blue light. The wearer has temporary
immunity to the effects of both natural and magical aging; the amulet
grows older instead of the wearer. As the amulet ages, it gradually
becomes dimmer. It can absorb 5d6 years of aging, at which time its
light dims completely, its magic negated, and the wearer resumes
Alternatively, you could cast Wish from a scroll to avoid the aging and penalties. Quoted from page 1068 in the section “Casting Scroll Effects” in the Encyclopedia Magica:
Spell components are unnecessary for a scroll reader, and no adverse
effects associated with casting the spell are suffered- these
requirements or penalties have been fulfilled or suffered by the
creator of the scroll.