title: Body mass index is associated with lumbar disc degeneration in young Finnish males: subsample of Northern Finland birth cohort study 1986.
abstract: BACKGROUND
  The role of environmental factors in lumbar intervertebral disc degeneration (DD) in young adults is largely unknown. Therefore, we investigated whether body mass index (BMI), smoking, and physical activity are associated with lumbar DD among young adults.
  
  
  METHODS
  The Oulu Back Study (OBS) is a subpopulation of the 1986 Northern Finland Birth Cohort (NFBC 1986) and it originally included 2,969 children. The OBS subjects received a postal questionnaire, and those who responded (N = 1,987) were invited to the physical examination. The participants (N = 874) were invited to lumbar MRI study. A total of 558 young adults (325 females and 233 males) underwent MRI that used a 1.5-T scanner at the mean age of 21. Each lumbar intervertebral disc was graded as normal (0), mildly (1), moderately (2), or severely (3) degenerated. We calculated a sum score of the lumbar DD, and analyzed the associations between environmental risk factors (smoking, physical activity and weight-related factors assessed at 16 and 19 years) and DD using ordinal logistic regression, the results being expressed as cumulative odds ratios (COR). All analyses were stratified by gender.
  
  
  RESULTS
  Of the 558 subjects, 256 (46%) had no DD, 117 (21%) had sum score of one, 93 (17%) sum score of two, and 92 (17%) sum score of three or higher. In the multivariate ordinal logistic regression model, BMI at 16 years (highest vs. lowest quartile) was associated with DD sum score among males (COR 2.35; 95% CI 1.19-4.65) but not among females (COR 1.29; 95% CI 0.72-2.32). Smoking of at least four pack-years was associated with DD among males, but not among females (COR 2.41; 95% CI 0.99-5.86 and 1.59; 95% 0.67-3.76, respectively). Self-reported physical activity was not associated with DD.
  
  
  CONCLUSIONS
  High BMI at 16 years was associated with lumbar DD at 21 years among young males but not among females. High pack-years of smoking showed a comparable association in males, while physical activity had no association with DD in either gender. These results suggest that environmental factors are associated with DD among young males.
authors.affiliation: Institute of Clinical Medicine, Department of Physical and Rehabilitation Medicine, University of Oulu, PL 5000, Oulu, 90014, Finland. janitaka@mail.student.oulu.fi
authors.forename: Jani
authors.initials: J
authors.lastname: Takatalo
authors.forename: Jaro
authors.initials: J
authors.lastname: Karppinen
authors.forename: Simo
authors.initials: S
authors.lastname: Taimela
authors.forename: Jaakko
authors.initials: J
authors.lastname: Niinimäki
authors.forename: Jaana
authors.initials: J
authors.lastname: Laitinen
authors.forename: Roberto
authors.initials: R
authors.lastname: Blanco Sequeiros
authors.forename: Markus
authors.initials: M
authors.lastname: Paananen
authors.forename: Jouko
authors.initials: J
authors.lastname: Remes
authors.forename: Simo
authors.initials: S
authors.lastname: Näyhä
authors.forename: Tuija
authors.initials: T
authors.lastname: Tammelin
authors.forename: Raija
authors.initials: R
authors.lastname: Korpelainen
authors.forename: Osmo
authors.initials: O
authors.lastname: Tervonen
mesh_terms: D015992:Body Mass Index; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000175:diagnosis / Q000453:epidemiology*; D008019:Life Style; D016015:Logistic Models; D008159:Lumbar Vertebrae / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D009043:Motor Activity; D016017:Odds Ratio; D010808:Physical Examination; D010809:Physical Fitness; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology; D011795:Surveys and Questionnaires; D055815:Young Adult