It is not clear why some people develop a prolapsed disc and not others, even when they do the same job or lift the same sort of objects. It seems that some people may have a weakness in the outer part of the affected disc. Various things may trigger the inner softer part of the disc to prolapse out through the weakened outer part of the disc. For example, sneezing, awkward bending, or heavy lifting in an awkward position may cause some extra pressure on the disc. In people with a weakness in a disc this may be sufficient to cause a prolapse. Factors that may increase the risk of developing a prolapsed disc include: a job involving lots of lifting, a job involving lots of sitting (especially driving), weight bearing sports (weight lifting etc), smoking, obesity and increasing age (a disc is more likely to develop a weakness with increasing age).