title: The dose-response relationship between cumulative lifting load and lumbar disk degeneration based on magnetic resonance imaging findings.
abstract: BACKGROUND
  Lumbar disk degeneration (LDD) has been related to heavy physical loading. However, the quantification of the exposure has been controversial, and the dose-response relationship with the LDD has not been established.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the dose-response relationship between lifetime cumulative lifting load and LDD.
  
  
  METHODS
  This was a cross-sectional study.
  
  
  METHODS
  Every participant received assessments with a questionnaire, magnetic resonance imaging (MRI) of the lumbar spine, and estimation of lumbar disk compression load. The MRI assessments included assessment of disk dehydration, annulus tear, disk height narrowing, bulging, protrusion, extrusion, sequestration, degenerative and spondylolytic spondylolisthesis, foramina narrowing, and nerve root compression on each lumbar disk level. The compression load was predicted using a biomechanical software system.
  
  
  RESULTS
  A total of 553 participants were recruited in this study and categorized into tertiles by cumulative lifting load (ie, <4.0 × 10(5), 4.0 × 10(5) to 8.9 × 10(6), and ≥8.9 × 10(6) Nh). The risk of LDD increased with cumulative lifting load. The best dose-response relationships were found at the L5-S1 disk level, in which high cumulative lifting load was associated with elevated odds ratios of 2.5 (95% confidence interval [95% CI]=1.5, 4.1) for dehydration and 4.1 (95% CI=1.9, 10.1) for disk height narrowing compared with low lifting load. Participants exposed to intermediate lifting load had an increased odds ratio of 2.1 (95% CI=1.3, 3.3) for bulging compared with low lifting load. The tests for trend were significant.
  
  
  CONCLUSIONS
  There is no "gold standard" assessment tool for measuring the lumbar compression load.
  
  
  CONCLUSIONS
  The results suggest a dose-response relationship between cumulative lifting load and LDD.
authors: Y-J. Hung, MS, Institute of Occupational Medicine and Industrial Hygiene, National Taiwan University (NTU), College of Public Health, Taipei, Taiwan, and Department of Biological Science and Technology, Chung Hwa University of Medical Technology, Tainan, Taiwan.
authors: Yu-Ju
authors: YJ
authors: Hung
authors: T.T-F. Shih, MD, Department of Medical Imaging and Radiology, NTU Hospital and NTU College of Medicine.
authors: Tiffany T-F
authors: TT
authors: Shih
authors: B-B. Chen, MD, Department of Medical Imaging and Radiology, NTU Hospital and NTU College of Medicine.
authors: Bang-Bin
authors: BB
authors: Chen
authors: Y-H. Hwang, PhD, Institute of Occupational Medicine and Industrial Hygiene, NTU College of Public Health.
authors: Yaw-Huei
authors: YH
authors: Hwang
authors: L-P. Ma, BS, Department of Environmental & Occupational Medicine, NTU Hospital and NTU College of Medicine.
authors: Li-Ping
authors: LP
authors: Ma
authors: W-C. Huang, MS, Department of Environmental & Occupational Medicine, NTU Hospital and NTU College of Medicine.
authors: Wen-Chuan
authors: WC
authors: Huang
authors: S-H. Liou, PhD, MD, Department of Public Health, National Defense Medical Center, Taipei, Taiwan, and Division of Environmental Health and Occupational Medicine, National Health Research Institute, Taipei, Taiwan.
authors: Saou-Hsing
authors: SH
authors: Liou
authors: I-K. Ho, PhD, Center for Drug Abuse and Addiction, China Medical University Hospital, Taichung, Taiwan; Graduate Institute of Clinical Medical Science, China Medical University, Taichung, Taiwan; and Neuropsychiatric Research Center, National Health Research Institute, Zhunan, Miaoli County, Taiwan.
authors: Ing-Kang
authors: IK
authors: Ho
authors: Y.L. Guo, PhD, MD, Department of Environmental & Occupational Medicine, NTU College of Medicine and NTU Hospital, Taipei, Taiwan, and Institute of Occupational Medicine and Industrial Hygiene, NTU College of Public Health, Room 339, No. 17, Xuzhou Rd, Taipei, Taiwan. leonguo@ntu.edu.tw.
authors: Yue L
authors: YL
authors: Guo
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000209:etiology* / Q000473:pathology*; D017770:Lifting / Q000009:adverse effects*; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009784:Occupational Diseases / Q000209:etiology* / Q000473:pathology*; D012307:Risk Factors; D016474:Weight-Bearing; D055815:Young Adult