title: Does physical activity moderate the relationship between depression symptomatology and low back pain? Cohort and co-twin control analyses nested in the longitudinal study of aging Danish twins (LSADT).
abstract: OBJECTIVE
  To investigate whether depression symptomatology is associated with low back pain (LBP) in twins aged 70+ and whether this effect depends on a person's physical activity (PA) status.
  
  
  METHODS
  This prospective cohort and nested case-control study used a nationally representative sample of twins. Data on depression symptomatology (modified Cambridge Mental Disorders Examination) and self-reported PA were obtained from the Longitudinal Study of Aging Danish Twins using twins without LBP at baseline. Associations between depression symptomatology (highest quartile) at baseline and LBP two years later were investigated using logistic regression analyses adjusted for sex. To examine the moderating effect of PA, we tested its interaction with depression. Associations were analysed using the complete sample of 2446 twins and a matched case-control analysis of 97 twin pairs discordant for LBP at follow-up. Odds ratios (OR) with 95% confidence intervals (CI) were calculated.
  
  
  RESULTS
  Using the whole sample, high depression scores were associated with an increased probability of LBP (OR 1.56, 95% CI 1.22-1.99, P ≤ 0.01). There was no statistically significant interaction of light PA and depression symptomatology (OR 0.78, 95% CI 0.46-1.35, P = 0.39) and strenuous PA and depression symptomatology (0.84, 95% CI 0.50-1.41, P = 0.51). The case-control analysis showed similar ORs, although statistically insignificant.
  
  
  CONCLUSIONS
  High depression symptomatology predicted incident LBP. This effect is supposedly not attributable to genetic or shared environmental factors. Physical activity did not moderate the effect of depression symptomatology on LBP.
authors.affiliation: Neuroscience Research Australia, The University of New South Wales, Sydney, New South Wales, Australia. m.huebscher@neura.edu.au.
authors.forename: Markus
authors.initials: M
authors.lastname: Hübscher
authors.affiliation: Department of Sports Science and Clinical Biomechanics and Nordic Institute of Chiropractic and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark.
authors.forename: Jan
authors.initials: J
authors.lastname: Hartvigsen
authors.affiliation: Faculty of Health Sciences, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Matthew
authors.initials: M
authors.lastname: Fernandez
authors.affiliation: Institute of Public Health, University of Southern Denmark, Odense, Denmark.
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
authors.affiliation: Faculty of Health Sciences, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Paulo
authors.initials: P
authors.lastname: Ferreira
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D016022:Case-Control Studies; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D003863:Depression / Q000453:epidemiology / Q000523:psychology*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D017116:Low Back Pain / Q000453:epidemiology / Q000503:physiopathology / Q000523:psychology*; D008297:Male; D009043:Motor Activity; D016017:Odds Ratio; D011446:Prospective Studies; D057566:Self Report; D014427:Twins
keywords: Depression symptomatology; Low back pain; Physical activity; Spinal pain; Twins