I wanted to know if degenerative disc disease is caused by aging or something else. In 2013 at the age of 36 I was given the MRI report: Moderate left-sided disc protrusion L4-L5 with severe thecal sac and left L5 nerve compression. The disc is degenerated and narrowed. Left-sided L4 pars defect. Mild bilateral facet join degeneration. Almost 3 years later I did another MRI: 2 mm spondylotic annular disc bulge with desiccation, moderate loss of disc height and reactive endplate changes. No central canal stenosis. Unremarkable facets. No foraminal stenosis. Previously seen disc protrusion has resolved. Degenerative disc disease has progressed. Does it mean my disc narrowing is caused by aging?I'm only 39, not overweight, in good shape, never smoked and live a healthy lifestyle but have a stressful job that also requires long work hours sitting in front of the computer and travel.