Smoking and intervertebral disc degeneration.

Cigarette smokers have an increased risk of low back pain which may be caused by disc degeneration and spinal instability, for example. Ischemia, apoptosis, faulty synthesis of disc macromolecules, and an imbalance between disc matrix proteinases and their inhibitors may be involved in the pathogenesis of disc degeneration. Along with degeneration, the primary avascular disc turns vascular. There is some evidence that disc degeneration of cigarette smokers is of more severe degree than that of non-smokers.Cigarette-smoking increases serum proteolytic activity by releasing proteolytic enzymes from neutrophils in alveolar capillaries, and by inhibiting the activity of alpha-1-antiprotease, the most potent protease inhibitor. We hypothesize that the high serum proteolytic activity of cigarette-smokers gets access to a previously degenerated neovascularized disc and speeds up the degerative process. The increased proteolytic activity may also weaken the spinal ligaments resulting in spinal instability. These processes may explain the increased risk of low back pain of cigarette smokers. Copyright 2001 Harcourt Publishers Ltd.