title: Cross-sectional magnetic resonance imaging study of lumbar disc degeneration in 200 healthy individuals.
abstract: OBJECTIVE
  The current cross-sectional observational MR imaging study aimed to investigate the prevalence and risk factors of lumbar disc degeneration in a healthy population and to establish the baseline data for a prospective longitudinal study.
  
  
  METHODS
  Two hundred healthy volunteers participated in this study after providing informed consent. The status of lumbar disc degeneration was assessed by 3 independent observers, who used sagittal T2-weighted MR imaging. Demographic data collected included age, sex, body mass index, episode(s) of low-back pain, smoking status, hours of standing and sitting, and Roland-Morris Disability Questionnaire scores. There were 68 men and 132 women whose mean age was 39.7 years (range 30-55 years). Eighty-two individuals (41%) were smokers, and the Roland-Morris Disability Questionnaire scores were averaged to 0.6/24.
  
  
  RESULTS
  The prevalence of disc degeneration was 7.0% in L1-2, 12.0% in L2-3, 15.5% in L3-4, 49.5% in L4-5, and 53.0% in L5-S1. A herniated disc was observed at the corresponding levels in 0.5, 3.5, 6.5, 25.0, and 35.0% of cases respectively. Spondylolisthesis was observed in < 3% of this population. Multiple logistic regression analysis demonstrated that age and hours sitting were significantly related to L4-5 disc herniation. Episode of low-back pain, smoking status, body mass index, and hours standing did not affect the prevalence of disc degeneration.
  
  
  CONCLUSIONS
  The current study established the baseline data of lumbar disc degeneration in a 30- to 55-year-old healthy population for a prospective longitudinal study. Hours spent sitting significantly increased the prevalence of disc herniation, but episode of low-back pain, smoking status, obesity, and standing hours were not significant risk factors.
authors.affiliation: Spine Center, Hakodate Central General Hospital, Hakodate, Hokkaido, Japan. mkanayama@aol.com
authors.forename: Masahiro
authors.initials: M
authors.lastname: Kanayama
authors.forename: Daisuke
authors.initials: D
authors.lastname: Togawa
authors.forename: Chihiro
authors.initials: C
authors.lastname: Takahashi
authors.forename: Tomoya
authors.initials: T
authors.lastname: Terai
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Hashimoto
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000453:epidemiology* / Q000473:pathology*; D007405:Intervertebral Disc Displacement / Q000453:epidemiology* / Q000473:pathology*; D016015:Logistic Models; D008137:Longitudinal Studies; D008159:Lumbar Vertebrae; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D011795:Surveys and Questionnaires