[Disposition]

Genes and your body's physical characteristics have a lot to do with it. I have a slipped disk in my neck from bad posture related to using missized chairs and desks while looking down at a 12" laptop for years and I'm not even 30 yet.

The combination of slouching your shoulders forward to keep your hands together and face-down for typing on a small keyboard, and looking down exacerbate such problems, faster for some than others—unless you happen have the build of a horse jockey.