Question: Can degenerative disc disease progress up or down the spine?

My wife’s physician told her that her lumbar degenerative disc disease is not related to her thoracic and cervical spine conditions. Her lower DDD was diagnosed over 15 years ago but since then her whole spine has deteriorated. Is the physician correct? Can degenerative disc disease in the lower lumbar progress all the way up into the thoracic and cervical spine? If so, is it directly caused by the DDD condition itself or the fact that the weakened vertebrae causes stress on additional vertebrae?

Degenerative disc disease is not a disease per se. It cannot spread and cannot be given to anyone else. Some people however have weak discs everywhere and they are prone to degenerating with time.