Interaction Between Occupational Exposure And Genetic Susceptibility On Lumbar Disc Degeneration

To explore the interaction between occupational exposure and genetic susceptibility on lumbar disc degeneration,a case-control study and an occupational epidemiologic survey were carried out,applying PCR-RFLP genetic polymorphism examination and Rothman additive model analysis.1.The effect of occupational exposure on Lumbar disc degenerationFor case-control study,178 cases were diagnosed as lumbar function abnormity by orthopedics and 284 residents without low back pain history were randomly recruited as controls.In non-conditional logistic analysis,it is indicated that family heritage,back injury history,work ergonomic factors(overload,bending,twisting and vibration) and age were significantly associated with lumbar disc degeneration;the ORs were 12.70,11.79,8.96,5.46,3.54 and 1.05 respectively(P＜0.05).In occupational epidemiologic survey,213 foundry workers,151 badminton makers and 53 office workers were recruited.After weighing work years,the ergonomic factors were analyzed,and the results showed that there was a rising tendency of lumbar disc degeneration,in terms of its incidence and degree,with the workload increasing,bending/twisting amplitude,prolonged sitting and standing.The highest incidence of lumbar disc degeneration was associated with the strongest exposure,including workload over 50 kg,bending amplitude over 60°,twisting amplitude over 30°and sitting/standing prolonged for more than 10 hours.2.The impact of genetic susceptibility on lumbar disc degenerationA case-control study involving 315 cases diagnosed as lumbar disc degeneration by CT and 543 controls was carried out to study the impact of genetic susceptibility on lumbar intervertebral disc degeneration.Polymerase chain reaction and restriction fragments length polymorphism(PCR-RFLP) were applied to detect the polymorphisms of MMP-3(matrix metalloproteinase-3),VDR-Taq(vitamin D receptor-Taq),VDR-Apa(vitamin D receptor-Apa),TGF-β1(transforming growth factor-β1) and IL-1α(interleukin-1α).The results showed that the frequencies of mutated genotypes of MMP-3 and VDR-Apa in lumbar disc degeneration cases were significantly higher than that in controls(OR=1.62 and 1.42 respectively,P＜0.05), while no difference for the distribution of VDR-Taq,TGF-β1 and 1L-1αmutated genotypes between the two groups was detected(P＞0.05).According to the image diagnosis,the degeneration severity of stuty cases were classified as degree 1 and degree 2.The determination of the effects of MMP-3, VDR-Taq,VDR-Apa,TGF-β1 and IL-1αpolymorphism on the degeneration severity was then followed for case group,it was found that individuals carried the mutated genotypes A of VDR-Apa and T of TGF-β1 got a higher risk of inducing lumbar disc degeneration in degree 2(P＜0.05).3.Interaction between occupational exposure and genetic Polymorphism on lumbar disc degenerationA case-control study including 314 lumbar disc degeneration cases and 543 healthy controls was carried out to study the interaction between work ergonomic factors and genetic polymorphism.Rothman's synergy index was applied to measure the synergistic interaction.The results showed that the interactive effect profoundly existed between the mutated genotype 5A of MMP-3 and bending(SI=1.93),and whole body vibration exposure(SI=12.01).Individuals who carried the mutated genotype 5A of MMP-3 exposed to high level of bending posture and whole body vibration got a significantly higher risk of suffering lumbar disc degeneration,the ORs were 9.80 and 6.39 respectively,and the impact attributed to synergetic effect were 35.2%and 82.3%.In conclusion,the work environment risks of lumbar disc degeneration are family heritage,back injury history,work ergonomic factors(overload,bending, twisting and vibration) and age.Subjects with mutation genotypes of MMP-3 and/or VDR-Apa seem to be more vulnerable to lumbar disc degeneration.There presented synergetic effect between the mutated genotype 5A of MMP-3 and bending posture, between the mutated genotype 5A of MMP-3 and whole body vibration.