The people of Aldous Huxley's Brave New World are preserved from diseases and aging. Their internal secretions are artificially balanced so that they maintain what is called "youthful equilibrium." They receive blood transfusions, their metabolism is permanently stimulated and they maintain mineral levels of youth. In this way, they remain looking young. Besides this, people are only allowed to live until they are sixty and then they are recycled into productive gases.
Because in her world one never sees anyone who truly looks old, Lenina is repulsed as she watches an old man on the savage reservation in Chapter Seven. His bent back, his wrinkled face, and his hobbled walk are horrifying to Lenina. In fact, she is so horrified by the experience of the ceremony that the old man directs that she wishes she had her soma with her.
They value there youthful appearances because they will not allow themselves to look old. When lenina goes to the savage reservation and sees the older person who is all destroyed they see what its like for someone to get old, and she was very upset by it.The alphas and betas will modify themselves so that they will never have to deal with getting old and having a body that will not work as well as it did when they were younger.