From The Ergoweb® Learning Center

Study: Physical Work Factors Dominate As Source of Carpal Tunnel Syndrome

In a cross sectional study of 1071 workers from a variety of work settings, carpal tunnel syndrome (CTS), defined as a combination of prolonged electrophysiological conduction time and appropriate symptoms in the same hand, was found to be independently associated with both personal and work-related risk factors including: 
• Lifting 2 or more pounds
• Using vibrating hand tools
• Using the fingers or thumb as a pressing tool
• Using the fingers in a pinch grip
• Forceful gripping
• Higher median wrist index (ration of depth to width)

The best predictive work-related indicators of carpal tunnel syndrome (CTS) were a combination of lifting 2 or more pounds, using vibrating hand tools and working on an assembly line.  Higher body mass index (BMI) was related to a case of CTS but not statistically significant.

When considering just CTS symptoms (positive hand findings but negative nerve conduction study), significant association was found with:
• Younger age
• Using vibrating tools
• Using a twisting motion of the forearm
• Using the fingers or thumb as a pressing tool
• Using the fingers in a pinch grip
• Forceful gripping

The Bottom Line – How This Applies To Ergonomists

This study revealed that CTS can develop solely from either personal or physical work factors, but physical work factors seem to be greater contributors.  Workers with a history of manual trade jobs were more likely to exhibit CTS. 

Other Significant Findings
1) Most of those who had a positive nerve conduction study (86.3 percent) did not have related median nerve hand symptoms.
2) Females were not at a higher risk than males.
3) Among the 1108 subjects, 18 had CTS and 131 had evidence of median neuropathy.
4) The study involved workers with 258 different job titles.

The authors felt that the strength of inferences drawn from their study was reduced by the low prevalence of CTS among their study population.  Also, there was a low prevalence of diabetes, arthritis, and hypothyroidism in the study group, which affected statistical models.

This research paper can be acquired at:;jsessionid=JPLQmnwQ270MyF76DWcGhz2JJ9G41QsqkvtTRlTHYpvhJ0GbLl2q!1321082991!181195629!8091!-1

Article Title: Risk Factors for Carpal Tunnel Syndrome and Median Neuropathy in a Working Population

Publication: Journal of Occupational and Environmental Medicine, 50 (12), 1355-1364, 2008

Authors: T N Armstrong, A M Dale, A Franzblau, and B A Evanoff

This article originally appeared in The Ergonomics Report™ on 2009-02-11.