Can age-related intervertebral disc changes be differentiated from degenerative disc disease?

Abstract

INTRODUCTION. It is known that intervertebral disc (IVD) degeneration progresses with age, and not all subjects with IVD degeneration have symptoms. We hypothesize symptomatic patients have a more severe form of IVD degeneration (degenerative disc disease) than can be accounted for by their age (age-related changes). METHODOLOGY. Making use of a large MRI and symptom database of 1244 individuals recruited from the population between 18 to 55 years of age, individuals with IVD degeneration were scored by their severity using the DDD score. For each age band, a mean DDD score is calculated and serve as the definition of age-related changes, while degenerative disc disease is defined as individuals that have a score deviated from the mean (>2 SD). Further, an age-adjusted DDD score is calculated based on a logarithmic transformation of the mean. The validity of this age-adjustment was then correlated with symptoms and previous genetic pre-disposition findings. RESULTS. After age-adjustment, individuals with a more severe form of degeneration than can be expected for their age could be identified. The age-adjusted DDD score of these individuals highly correlated with low back pain (LBP) (p 0.0001), whereas without age adjustment, the DDD score only weakly correlated with LBP (p0.024). All previously identified genetic pre-disposing factors could be reproduced using the new score. DISCUSSION. This study is unique and made possible only by the large population database of MRI information. It supports the hypothesis that age-related changes in the IVD occurs, and that this can be differentiated from symptomatic degenerative disc disease. This is an important concept not only as a phenotype for genetic studies, but for clinicians and patients to accept age-related changes, which do not necessarily need treatment, whereas those with degenerative disc disease are much more likely to be symptomatic and early treatment should be contemplated.