She said: "I don't know how I'll cope with ageing - I better start figuring it out. I feel my knees changing - like, why do I have this pain when I'm running on the treadmill? What's going on with my lower back when I wake up in the morning? I just feel changes.
"And I'm definitely fearful in a very vain manner about my body ageing. I think it's freaky weird to look at a picture of your grandmother when she was a young woman and look at her now."
Despite worrying about the onslaught of wrinkles, Jessica insists she will never resort to cosmetic surgery to keep her looking young.
She added to Britain's Marie Claire magazine: "I am really afraid of blades on my face - that freaks me out beyond belief. I would way rather have wrinkles than have some slice-up going on."
Jessica Biel is petrified of ageing.
