Gerontophobia

Gerontophobia is the fear of age-related self-degeneration (similar to Gerascophobia), or a hatred or fear of the elderly due to memento mori. The term comes from the Greek γέρων – "gerōn", "old man" and φόβος – "phobos", "fear".
Ageism.
Discriminatory aspects of ageism have been strongly linked to gerontophobia. This irrational fear or hatred of the elderly is associated with the fact that someday all young people including oneself will be old inevitably and suffer from the irreversible health decline that comes with old age, which is associated with disability, disease and death. The sight of aged people is a reminder of death ("memento mori") and inevitable biological vulnerability. This unwillingness to accept these manifests in feelings of hostility and discriminatory acts towards the elderly.