Interleukin 1 polymorphisms and intervertebral disc degeneration

Background: Enzymatic breakdown of the extracellular matrix, and possibly local inflammation, contributes to intervertebral disc degeneration. We investigated whether polymorphisms within the IL-1 gene locus are associated with lumbar disc degeneration and whether the effect of occupational physical load on disc degeneration is modified by the polymorphisms. Methods: Genotypes were determined from 133 middle-aged men who underwent magnetic resonance imaging of the lumbar spine. The participants represented 3 occupations: 40 were machine drivers, 42 carpenters, and 51 office workers. We evaluated decreased signal intensity of the nucleus pulposus, disc bulges, and decreased disc height as signs of degeneration in the L2/L3-L5/S1 discs. Results: The odds ratio for disc bulges was 2.4 (95% confidence interval = 1.2-4.8) and 1.9 (1.0-3.7), in carriers of the IL-1alphaT(889) or IL-1betaT(3954) alleles, respectively. The TT genotype of the IL-1alpha gene carried more than 3-fold risk of disc bulges as compared with the CC genotype. Conclusions: IL-1 gene cluster polymorphisms could affect the risk of disc degeneration. The effect of physical workload seems to be modified by the IL-1 gene polymorphisms.