Job strain, iso-strain, and the incidence of low back and neck injuries. A 7.5-year prospective study of San Francisco transit operators.

Work-related musculoskeletal disorders account for the largest single category of lost-time occupational injury or disease episodes in industrialized countries. In this study we analyzed the impact of the psychosocial work environment, conceptualized by the demand-control-support model, on the incidence of low back and neck injury in a cohort of 1221 public transit operators followed for 7 years and 6 months. The two main exposure variables were "job strain" (mismatch of high psychological demands and low decision latitude) and "iso-strain" (job strain plus exposure to low social support at work). Analyses controlled for demographic factors, physical workload, and pain at baseline. For low back injuries, increased hazard rates were found for job strain and iso-strain based on tertiles, with hazard ratios (HR) of 1.30 (95% CI=0.96-1.75) and 1.41 (95% CI=0.98-2.01), respectively. Job strain and iso-strain based on median split or analyzed as continuous variables were not associated with low back injuries. For neck injuries, job strain and iso-strain based on median split showed HRs of 1.27 (95% CI=0.99-1.63) and 1.33 (95% CI=1.01-1.77), respectively. Job strain and iso-strain based on tertiles had HRs of 1.52 (95% CI=1.13-2.05) and 1.73 (95% CI=1.21-2.45), respectively. When analyzed as continuous variables, a one-point increase on the job strain and iso-strain scales led to an 8% (95% CI=0.98-1.19) and 14% (95% CI=1.02-1.27) increased hazard of neck injuries, respectively. This study shows the importance of the psychosocial work environment in the etiology of musculoskeletal injuries among transit operators. Since reviews have shown that psychosocial workplace conditions in this occupational group can be changed, these findings indicate a potential for prevention at the workplace.

[1]  Robert Karasek,et al.  Healthy Work : Stress, Productivity, and the Reconstruction of Working Life , 1990 .

[2]  R A Deyo,et al.  Use of the International Classification of Diseases (ICD‐9‐CM) to Identify Hospitalizations for Mechanical Low Back Problems in Administrative Databases , 1992, Spine.

[3]  T. Chandola,et al.  The measurement of effort-reward imbalance at work: European comparisons. , 2004, Social science & medicine.

[4]  T. J. Sullivan,et al.  Determinants of duration of disability and return-to-work after work-related injury and illness: challenges for future research. , 2001, American journal of industrial medicine.

[5]  P. Landsbergis,et al.  Is job strain a major source of cardiovascular disease risk? , 2004, Scandinavian journal of work, environment & health.

[6]  J M Fisher,et al.  1998 Volvo Award Winner in Clinical Studies: Psychosocial Job Factors, Physical Workload, and Incidence of Work‐Related Spinal Injury: A 5‐Year Prospective Study of Urban Transit Operators , 1998, Spine.

[7]  S. Moon,et al.  An ecological model of musculoskeletal disorders in office work , 1996 .

[8]  Don B. Chaffin,et al.  Occupational low back pain : assessment, treatment, and prevention , 1992 .

[9]  David R. Ragland,et al.  Objective measurement of occupational stress factors--an example with San Francisco urban transit operators. , 1997 .

[10]  A. Bandura.  Self-Efficacy: The Exercise of Control , 1997, Journal of Cognitive Psychotherapy.

[11]  K. Belkic,et al.  The central nervous system: bridge between the external milieu and the cardiovascular system. , 2000, Occupational medicine.

[12]  T S Kristensen,et al.  Job stress and cardiovascular disease: a theoretic critical review. , 1996, Journal of occupational health psychology.

[13]  B. Aust,et al.  Comprehensive health promotion interventions at the workplace: experiences with health circles in Germany. , 2004, Journal of occupational health psychology.

[14]  N. Kawakami,et al.  The Job Content Questionnaire (JCQ): an instrument for internationally comparative assessments of psychosocial job characteristics. , 1998, Journal of occupational health psychology.

[15]  P. Brodal.  The Central Nervous System , 1992 .

[16]  S A Stansfeld,et al.  Occupational back pain--an unhelpful polemic. , 1995, Scandinavian journal of work, environment & health.

[17]  W. Fordyce,et al.  A Prospective Study of Work Perceptions and Psychosocial Factors Affecting the Report of Back Injury , 1991, Spine.

[18]  B. Aust,et al.  Stress prevention in bus drivers: evaluation of 13 natural experiments. , 2000, Journal of occupational health psychology.

[19]  Michiel A. J. Kompier,et al.  A Critical Examination of the Demand-Control-Support Model from a Work Psychological Perspective , 1997 .

[20]  C. Heaney,et al.  The relationship between psychosocial work characteristics and low back pain: underlying methodological issues. , 2000, Clinical biomechanics.

[21]  T. Skov,et al.  Psychosocial and physical risk factors for musculoskeletal disorders of the neck, shoulders, and lower back in salespeople. , 1996, Occupational and environmental medicine.

[22]  D G Wilder,et al.  Whole-body vibration exposure in subway cars and review of adverse health effects. , 1991, Journal of occupational medicine. : official publication of the Industrial Medical Association.

[23]  J. Schwartz,et al.  Association between ambulatory blood pressure and alternative formulations of job strain. , 1994, Scandinavian journal of work, environment & health.

[24]  J M Fisher,et al.  Psychosocial job factors associated with back and neck pain in public transit operators. , 1997, Scandinavian journal of work, environment & health.

[25]  S. Kjeldsen,et al.  Evidence for mediating econeurocardiologic mechanisms. , 2000, Occupational medicine.

[26]  M. Mulder,et al.  The incorporation of different demand concepts in the job demand-control model: effects on health care professionals. , 1999, Social science & medicine.

[27]  Robert Karasek,et al.  Current issues relating to psychosocial job strain and cardiovascular disease research. , 1998, Journal of occupational health psychology.

[28]  J M Fisher,et al.  Physical Workload and Ergonomic Factors Associated With Prevalence of Back and Neck Pain in Urban Transit Operators , 1997, Spine.

[29]  Harald Hannerz,et al.  Socioeconomic status and psychosocial work environment: results from a Danish national study , 2002, Scandinavian journal of public health. Supplement.

[30]  P M Bongers,et al.  Psychosocial risk factors for neck pain: a systematic review. , 2001, American journal of industrial medicine.

[31]  Reiner Rugulies,et al.  Physical workload, ergonomic problems, and incidence of low back injury: a 7.5-year prospective study of San Francisco transit operators. , 2004, American journal of industrial medicine.

[32]  P. Côté,et al.  The Saskatchewan Health and Back Pain Survey: The Prevalence of Neck Pain and Related Disability in Saskatchewan Adults , 1998, Spine.

[33]  R W Norman,et al.  Biomechanical and psychosocial risk factors for low back pain at work. , 2001, American journal of public health.

[34]  R Nordemar,et al.  Pain thresholds during standardized psychological stress in relation to perceived psychosocial work situation. Stockholm Music I Study Group. , 1993, Journal of psychosomatic research.

[35]  Bryson Dd,et al.  Suggested techniques for producing a partial prosthesis from silicone rubber. , 1965 .

[36]  S. Kasl,et al.  Measuring job stressors and studying the health impact of the work environment: an epidemiologic commentary. , 1998, Journal of occupational health psychology.

[37]  S. Moon,et al.  Somatic interpretation in cumulative trauma disorders , 1996 .

[38]  G. Elfström,et al.  Intravital dynamic pressure measurements in lumbar discs. A study of common movements, maneuvers and exercises. , 1970, Scandinavian journal of rehabilitation medicine. Supplement.

[39]  P. Landrigan,et al.  Occupational injury and illness in the United States. Estimates of costs, morbidity, and mortality. , 1997, Archives of internal medicine.