What does this weird dream mean?

I've had this dream a couple times, and it is quite weird, though I have experienced it more than once. The dream is in black and white, and the streets are empty, but me. Out of nowhere, old people come lurching out, like zombies. Basically, I'm being attacked by old people in my dream, and stalked by them. After the old people have surrounded where I live (in these dreams), there's always one who manages to get in, and they sneak up behind me and bite my neck, then everything goes black and the dream ends. What could this weird dream mean? Why do I have dreams of getting attacked by old people? Does this have any meaning? After I have these dreams, well I cant help but feel freaked out of old people, even though i know theyre harmless, but still... Anyhow, what does this dream mean? I've had it a few times. What does it mean when one is stalked by the old??? Basically, it's like a zombie movie, only im being attacked by the old instead of zombies. What does this mean???