Is working with colleagues in flexible employment a risk factor for carpal tunnel syndrome?

Introduction
Carpal tunnel syndrome (CTS) is a major health problem among workers. The aim of the study was to examine the risk factors for CTS in workers of a large French working population.

Methods
A total of 3,710 workers representative of a French region’s working population were randomly included in the study between 2002 and 2005. A total of 134 cases of CTS were diagnosed by 83 trained occupational physicians performing a standardized physical examination that strictly applied the methodology and clinical tests of the ‘Criteria document for evaluation of the work-relatedness of upper extremity musculoskeletal disorders’ (2001). Individual factors and work exposure were assessed by a self-administered questionnaire. Statistical associations between CTS and individual and work-related factors were analyzed using logistic regression modeling. 

Results
The personal risk factors for CTS were age (Odd Ratios (OR) up to 3.5 [95% CI 2.2-3.1] after 50 years), female gender (OR=2.2 [1.5-3.2]) and obesity (OR=1.9 [1.1-3.2]). The work-related risk factors were the high repetitiveness of the task (≥4h/day) without recovery period (OR=1.7 [1.0-3.0]), use of vibrating hand tools (≥4h/day) (OR=1.8 [1.1-2.9]), sustained or repeated wrist deviation (≥2h/day) combined with high perceived physical demand (OR=1.8 [1.1-2.9]), high psychological demand of the task (OR=1.5 [1.0–2.1]) and low social support from colleagues (OR=1.5 [1.0–2.3]). Three factors related to the work organization were associated with CTS: paced work dependant on quantified targets (OR=1.5 [1.0-2.3]), frequent changes of job/task during the week (OR=1.5 [1.0-2.8]) and work with colleagues in flexible employment (OR=1.6 [1.1-2.3]).

Discussion
Personal and work-related physical, psychosocial and organizational factors were associated with CTS. Working with colleagues in flexible employment seemed to be a risk factor for CTS in this large working population, independently of exposure to biomechanical and psychosocial risk factors.