title: Mapping the association between back pain and type 2 diabetes: A cross-sectional and longitudinal study of adult Spanish twins.
abstract: BACKGROUND
  Back pain and type 2 diabetes often co-occur, resulting in greater impact on people's health and complexity in their care. Plausible causal mechanisms for this association have been proposed, yet the nature of the link remains unclear. We therefore explored the direction of the association between type 2 diabetes and chronic back pain in twins, controlling for genetics and early environmental confounding.
  
  
  METHODS
  2,096 and 1,098 twins were included in the cross-sectional and longitudinal analyses, respectively. Any or severe (≥ 9) low back pain (LBP), neck pain (NP), and spinal pain (concurrent LBP and NP) and type 2 diabetes were investigated. Sequential analyses were performed using logistic regression. Firstly, twins were analysed unpaired (adjusted age and gender): total sample analyses. Then, to control for genetic and shared environmental factors, a co-twin case-control analysis was performed including monozygotic and dizygotic twin pairs discordant for back pain (cross-sectional only).
  
  
  RESULTS
  In the cross-sectional total sample analyses, type 2 diabetes was associated with chronic spinal pain (OR 1.61; 95%CI 1.12 to 2.31), severe chronic spinal pain (OR 3.33; 95%CI 1.47 to 7.53), chronic NP (OR 1.37; 95%CI 1.01 to 1.85), severe chronic NP (OR 2.28; 95%CI 1.24 to 4.21), and severe chronic LBP (OR 1.63; 95%CI 1.00 to 2.64). After further adjustment for genetic and shared environmental factors, none of the associations remained significant. The longitudinal analyses indicated that the presence of type 2 diabetes did not increase the risk of future back pain, or vice-versa, after two to four years.
  
  
  CONCLUSIONS
  Chronic back pain (spinal pain, NP, or LBP) was associated with the prevalence of type 2 diabetes. Associations are stronger for severe cases of pain. Future research should investigate the temporal relationships between these conditions with longer follow up in twins.
authors.affiliation: Faculty of Health Sciences, The University of Sydney, Sydney, NSW, Australia.
authors.forename: Amabile
authors.identifier: http://orcid.org/0000-0002-4818-7017
authors.initials: A
authors.lastname: Dario
authors.affiliation: The George Institute for Global Health, Sydney Medical School, The University of Sydney, Sydney, NSW, Australia.|Institute of Bone and Joint Research, Sydney Medical School, The University of Sydney, Sydney, NSW, Australia.
authors.forename: Manuela
authors.initials: M
authors.lastname: Ferreira
authors.affiliation: Faculty of Health Sciences, The University of Sydney, Sydney, NSW, Australia.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Refshauge
authors.affiliation: Faculty of Health Sciences, The University of Sydney, Sydney, NSW, Australia.
authors.forename: Alison
authors.initials: A
authors.lastname: Harmer
authors.affiliation: Murcia Twin Registry, Department of Human Anatomy and Psychobiology, University of Murcia, Murcia, Spain.|Biomedical Research Institute of Murcia (IMIB-Arrixaca-UMU), University Clinical Hospital "Virgen de la Arrixaca", Murcia, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Sánchez-Romera
authors.affiliation: Murcia Twin Registry, Department of Human Anatomy and Psychobiology, University of Murcia, Murcia, Spain.|Biomedical Research Institute of Murcia (IMIB-Arrixaca-UMU), University Clinical Hospital "Virgen de la Arrixaca", Murcia, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Pérez-Riquelme
authors.affiliation: Department of Physiotherapy, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Ligia
authors.initials: L
authors.lastname: Cisneros
authors.affiliation: Murcia Twin Registry, Department of Human Anatomy and Psychobiology, University of Murcia, Murcia, Spain.|Biomedical Research Institute of Murcia (IMIB-Arrixaca-UMU), University Clinical Hospital "Virgen de la Arrixaca", Murcia, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Ordoñana
authors.affiliation: Faculty of Health Sciences, The University of Sydney, Sydney, NSW, Australia.
authors.forename: Paulo
authors.initials: P
authors.lastname: Ferreira
mesh_terms: D059350:Chronic Pain / Q000453:epidemiology; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D017116:Low Back Pain / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D019547:Neck Pain / Q000453:epidemiology; D015995:Prevalence; D012042:Registries; D012306:Risk; D012737:Sex Factors; D013030:Spain / Q000453:epidemiology; D013131:Spine; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic