Although the etiology of most degenerative changes in the lumbar spine
is unclear, genetic factors may play an important role. To investigate this
link, we reviewed magnetic resonance images of the lumbar spines of
identical twins to assess the degree of similarities in degenerative
findings in the discs. Observers who were blinded to twinship evaluated
sagittal T1-weighted and T2-weighted magnetic resonance images of the
lumbar spines of forty male identical twins (twenty pairs) with respect to
changes in the end plates, desiccation of the discs, bulging or herniated
discs, and decrease in the height of the disc space. Similarities between
co-twins were significantly greater than would be expected by chance.
Whereas smoking status and age explained 0 to 15 per cent of the
variability in the various degenerative findings in the discs, 26 to 72 per
cent of the variability was explained with the addition of a variable
representing co-twin status. These findings are compatible with a marked
genetic influence and warrant further investigation.