Physical workload, low back pain and neck–shoulder pain: a Swedish twin study

Objectives: To investigate if high physical workload is associated with low back pain (LBP) and/or neck–shoulder pain (NSP) when taking into account the influence of genetic and shared environmental factors. Further, the study aims to explore the potential influence of genetic and shared environmental factors in the associations between high physical workload and the three disorder subgroups: solely LBP, solely NSP, and concurrent LBP and NSP. Methods: Data on 16 107 monozygotic and dizygotic twins, born during 1959–1985, were obtained from a cross-sectional study, performed in 2005–2006 by the Swedish Twin Registry. Odds ratios (ORs) calculated in cohort analyses and co-twin control analyses were used to assess the associations between high physical workload and LBP and NSP when controlling for genetic and shared environmental factors. Results: In the cohort analysis, the association between high physical workload and the group with any one symptom (LBP and/or NSP) was OR 1.47 (95% CI 1.37 to 1.57). The co-twin control analyses indicated that the association was not confounded by genetic and shared environmental factors with OR 1.34 (95% CI 1.02 to 1.75) for dizygotic twins and OR 1.44 (95% CI 1.06 to 1.95) for monozygotic twins. In the cohort analyses the association with high physical workload was higher for concurrent LBP and NSP (OR 1.80 (95% CI 1.62 to 1.99)) than for solely LBP (OR 1.41 (95% CI 1.27 to 1.57)) and solely NSP (OR 1.31 (95% CI 1.20 to 1.43)). Concurrent LBP and NSP was the only group that showed a stepwise decrease of the point estimates between the cohort analysis and the co-twin control analyses, OR 1.71 (95% CI 1.00 to 2.94) for dizygotic twins, and OR 1.29 (95% CI 0.64 to 2.59) for monozygotic twins indicating confounding by genetic and shared environmental factors. Conclusions: High physical workload was associated with LBP and/or NSP even after adjusting for genetic or shared environmental factors. Only for concurrent LBP and NSP, genetic and shared environmental factors seemed to have an influence on the association with high physical workload.

[1]  M. Nordin,et al.  Implications of the Bone and Joint Decade 2000 – 2010 Task Force on Neck Pain and Its Associated Disorders From Concepts and Findings to Recommendations , 2008 .

[2]  Margareta Nordin,et al.  Association of Comorbidity and Outcome in Episodes of Nonspecific Low Back Pain in Occupational Populations , 2002, Journal of occupational and environmental medicine.

[3]  C. Wiktorin,et al.  Sickness absence and concurrent low back and neck–shoulder pain: results from the MUSIC-Norrtälje study , 2006, European Spine Journal.

[4]  Å. Kilbom,et al.  Gender differences in upper extremity musculoskeletal complaints in the working population , 2000, International archives of occupational and environmental health.

[5]  Pierre Côté,et al.  Incidence and Course of Low Back Pain Episodes in the General Population , 2005, Spine.

[6]  S Lings,et al.  Ambiguous relation between physical workload and low back pain: a twin control study , 2003, Occupational and environmental medicine.

[7]  S. Dworkin,et al.  Grading the severity of chronic pain , 1992, Pain.

[8]  R. Shelerud.  Epidemiology of occupational low back pain. , 2006, Clinics in occupational and environmental medicine.

[9]  Allard J van der Beek,et al.  Gender Differences in Self-Reported Physical and Psychosocial Exposures in Jobs With Both Female and Male Workers , 2005, Journal of occupational and environmental medicine.

[10]  Scott Haldeman,et al.  The burden and determinants of neck pain in workers: results of the Bone and Joint Decade 2000-2010 Task Force on Neck Pain and Its Associated Disorders. , 2009, Journal of manipulative and physiological therapeutics.

[11]  J. Caro,et al.  PSY28 A SYSTEMATIC REVIEW OF LOW BACK PAIN COST OF ILLNESS STUDIES IN THE UNITED STATES AND INTERNATIONALLY , 2008 .

[12]  K. Christensen,et al.  Genetic and Environmental Contributions to Back Pain in Old Age: A Study of 2,108 Danish Twins Aged 70 and Older , 2004, Spine.

[13]  K. Kyvik,et al.  The prevalence of neck pain in the world population: a systematic critical review of the literature , 2006, European Spine Journal.

[14]  Research Priorities and Methodological Implications: The Bone and Joint Decade 2000–2010 Task Force on Neck Pain and Its Associated Disorders , 2008, Spine.

[15]  P. Lichtenstein,et al.  The Swedish Twin Registry: a unique resource for clinical, epidemiological and genetic studies , 2002, Journal of internal medicine.

[16]  Ilse de Bourdeaudhuij,et al.  Low back pain, disability and back pain myths in a community sample: prevalence and interrelationships , 2004, European journal of pain.

[17]  M. Nordin,et al.  The Burden and Determinants of Neck Pain in the General Population: Results of the Bone and Joint Decade 2000–2010 Task Force on Neck Pain and Its Associated Disorders , 2008, Spine.

[18]  D. Haynor,et al.  Similarities in degenerative findings on magnetic resonance images of the lumbar spines of identical twins. , 1995, The Journal of bone and joint surgery. American volume.

[19]  K. Christensen,et al.  Small Effect of Genetic Factors on Neck Pain in Old Age: A Study of 2,108 Danish Twins 70 Years of Age and Older , 2005, Spine.

[20]  D. Posthuma,et al.  Theory and practice in quantitative genetics. , 2003, Twin research : the official journal of the International Society for Twin Studies.

[21]  K. Kyvik,et al.  Heredity of Low Back Pain in a Young Population: A Classical Twin Study , 2004, Twin Research.

[22]  M. Nordin,et al.  The burden and determinants of neck pain in the general population: results of the Bone and Joint Decade 2000-2010 Task Force on Neck Pain and Its Associated Disorders. , 2009, Journal of manipulative and physiological therapeutics.

[23]  M. McGue.  When assessing twin concordance, use the probandwise not the pairwise rate. , 1992, Schizophrenia bulletin.

[24]  Linda J. Carroll,et al.  Research priorities and methodological implications: the Bone and Joint Decade 2000-2010 Task Force on Neck Pain and Its Associated Disorders. , 2009, Journal of manipulative and physiological therapeutics.

[25]  N. Manek,et al.  Epidemiology of back disorders: prevalence, risk factors, and prognosis , 2005, Current opinion in rheumatology.

[26]  Tim D Spector,et al.  Structural, psychological, and genetic influences on low back and neck pain: a study of adult female twins. , 2004, Arthritis and rheumatism.

[27]  J. Hartvigsen,et al.  Heritability of neck pain: a population-based study of 33,794 Danish twins. , 2006, Rheumatology.

[28]  Alf L. Nachemson,et al.  Neck and back pain : The scientific evidence of causes, diagnosis, and treatment , 2000 .

[29]  T. Armstrong,et al.  Test-retest reliability of an upper-extremity discomfort questionnaire in an industrial population. , 1997, Scandinavian journal of work, environment & health.

[30]  O Axelson,et al.  Interpretation of "negative" studies in occupational epidemiology. , 1990, Scandinavian journal of work, environment & health.

[31]  Linda J. Carroll,et al.  Course and Prognostic Factors for Neck Pain in Whiplash-Associated Disorders (WAD): Results of the Bone and Joint Decade 2000–2010 Task Force on Neck Pain and Its Associated Disorders , 2008, Spine.

[32]  L. Punnett,et al.  Estimating the global burden of low back pain attributable to combined occupational exposures. , 2005, American journal of industrial medicine.

[33]  Samuli Ripatti,et al.  Determinants of the Progression in Lumbar Degeneration: A 5-Year Follow-up Study of Adult Male Monozygotic Twins , 2006, Spine.

[34]  K. Kyvik,et al.  Heredity of low back pain in a young population: a classical twin study. , 2004, Twin research : the official journal of the International Society for Twin Studies.

[35]  C. Wiktorin,et al.  The influence of work-related exposures on the prognosis of neck/shoulder pain , 2007, European Spine Journal.

[36]  K. Kurppa,et al.  Genetic and environmental factors in sciatica. Evidence from a nationwide panel of 9365 adult twin pairs. , 1989, Annals of medicine.

[37]  P. Östlin.  Occupational career and health : methodological considerations on the healthy worker effect , 1989 .

[38]  Francesco Forastiere,et al.  Methodological issues regarding confounding and exposure misclassification in epidemiological studies of occupational exposures. , 2007, American journal of industrial medicine.

[39]  B. Jonsson,et al.  Standardised Nordic questionnaires for the analysis of musculoskeletal symptoms. , 1987, Applied ergonomics.

[40]  B. Bengtsson,et al.  Back pain: a study of twins. , 1991, Acta geneticae medicae et gemellologiae.

[41]  T. Hansson,et al.  The costs for persons sick-listed more than one month because of low back or neck problems. A two-year prospective study of Swedish patients , 2005, European Spine Journal.

[42]  Allard J van der Beek,et al.  Gender differences in the relations between work-related physical and psychosocial risk factors and musculoskeletal complaints. , 2004, Scandinavian journal of work, environment & health.

[43]  J. Caro,et al.  A systematic review of low back pain cost of illness studies in the United States and internationally. , 2008, The spine journal : official journal of the North American Spine Society.