Risk Factors for Lumbar Intervertebral Disc Height Narrowing -Ten Years Retrospective Cohort Study

INTRODUCTION: The intervertebral disc (IVD) is fibro-cartilaginous structures, composed of two major regions; the outer ring, called annulus fibrosus and the inner part, called the nucleus pulposus. These different tissues including cellular components maintain the metabolism of IVD and play an important role in mechanical function of spine. IVD is well known to degenerate by age, however the cause and pathophygiology of IVD degeneration has not been completely elucidated. Clinically, disc-space narrowing is the most commonly used specific finding to indicate IVD degeneration. It is generally believed that the progression of disc degeneration is associated with low back pain and with the progression of degenerative lumbar diseases. However, few data exist concerning the natural history of lumbar disc degeneration and its associated risk factors. To date, there are only a few reports of longitudinal studies on the progression of lumbar disc degeneration [1-3]. In addition, no cohort study has been reported in which lumbar disc height was quantitatively evaluated. The purpose of this study was (1) to quantitatively evaluate the change in lumbar disc height by radiographic measurement during ten years in a population-based cohort study and (2) to investigate risk factors for the development of disc height narrowing.