That hump is called kyphosis and is usually related to osteoporosis. Osteoporosis is thinning of the bones associated with aging and is sometimes hereditary. The bones in the back become thin, and areas of weakness compress into the shape of a wedge. This often results in the outward curving of the spine. It does make sense that if a person is slouching constantly while these spine bones are thinning, the spine will more readily compress in that "slouched" direction. In your case, it is most likely a result of the other factors, such as osteoporosis. If you have not done so already, it would be a good idea to have your bone density checked to see if that is a problem.