From The Ergoweb® Learning Center

Risk Factors Shown to Have Multiplicative Affect on Incidence of Musculoskeletal Symptoms

Video Display Terminal (VDT) workers who were exposed to risk factors of awkward posture and psychological job strain demonstrated: 

  • Among males, a significantly higher risk for the development of low back symptoms with functional limitations when compared to being exposed to awkward posture or psychological job strain individually.
  • Among females, a higher but statistically insignificant risk for the development of neck/shoulder, low back, and forearm/wrist/hand symptoms with functional limitations when compared to being exposed to awkward posture or psychological job strain individually.

The study involved 2,431 public sector, white collar employees in Québec City, Canada, who completed self assessments involving the risk factors and symptoms/limitations at baseline and at follow-up approximately three years later.

The incidence of regional symptoms with functional deficits during the six months period prior to the follow-up questionnaire was:

  • At the neck/shoulder, 7.0 percent for males and 11.1 percent for females
  • At the low back, 10.0 percent for males and 10.6 percent for females
  • At the forearm/wrist/hand, 5.6 percent for males and 7.6 percent for females

The Bottom Line – How This Applies To Ergonomists

Concurrent exposure to awkward posture and job strain risk factors produces an interactive affect which multiplicatively increases the incidence of musculoskeletal symptoms along with diminished regional function among VDT users for select body regions.  Reducing/controlling even one of the risk factors will yield a benefit of lessening the incidence of musculoskeletal symptoms produced by the interaction affect.

Other Key Points

Participants occupied various professions (i.e., technicians, office workers, middle managers).

After applying inclusion/exclusion criteria, the study was comprised of 1342, 1294, and 1466 subjects respectively for neck/shoulder, low back and forearm/wrist/hand symptom development.

Social support was not found to impact the incidence of musculoskeletal symptoms when there was high job strain.

Research Procedure

Subjects filled out a self-administered survey that had queries involving workplace characteristics (job strain and postural risk factors) and their health (musculoskeletal symptoms).  The evaluations were performed twice: at baseline (between June 2000 and June 2003) and follow-up (between October 2004 and November 2006) with a mean follow-up time of 3.2 years. 

Participant inclusion criteria was defined as:

  • At baseline, being between 18 and 60 years of age
  • At baseline, having worked at least one year for the entity
  • At baseline and follow-up, working a minimum of 25 hours/week
  • Having no more than 59 leave of absence days during the study period

Baseline subject exclusion criteria included pregnancy, musculoskeletal inflammatory diseases (i.e., rheumatoid arthritis), and regional disorders involving the body areas of concern for this analysis (neck/shoulder, forearm/wrist/hand, or low back).  Follow-up exclusion criteria included spending less than four hours per day interacting with a computer.

Job strain was evaluated through questions that addressed work psychological demands and decision latitude.  Social support, a possible mechanism that tempers job strain, was also measured.  The Health Canada ergonomic guidelines provided guidance in determining questions relative to VDT postural risk factors exposure.

An altered version of the Nordic questionnaire was used to identify musculoskeletal symptoms.   A case study was considered to be, in the prior six months, the experience of:

  • Musculoskeletal pain, ache, or discomfort, and
  • Reduced regional part function at work, home, or when performing leisure activities

A series of cofactors were also tracked including gender, age, marital status, highest level of education, smoking status, and body mass index.

Article Title: Interaction between postural risk factors and job strain on self-reported musculoskeletal symptoms among users of video display units: a three-year prospective study

Publication: Scandinavian Journal of Work, Environment & Health, 35 (2):134-144, 2009

Authors: J Lapointe, C E Dionne, C Brisson, S Montreuil

This article originally appeared in The Ergonomics Report™ on 2009-07-29.