A1834 Gender differences in carpal tunnel syndrome: validity of ACGIH TLV for hand activity in an heterogeneous occupational cohort

Monday, March 19, 2012
Ground Floor (Cancun Center)
Roberta Bonfiglioli, Department of Internal Medicine, Geriatrics and Nephrology, University Of Bologna, Bologna, Italy
Stefano Mattioli, Department of Internal Medicine, Geriatrics and Nephrology, University Of Bologna, Bologna, Italy
Thomas J. Armstrong, Center for Ergonomics, University Of Michigan, Ann Arbor, United States
Francesca Graziosi, Department of Internal Medicine, Geriatrics and Nephrology, University of Bologna, Bologna, Italy
Francesco Marinelli, Occupational Medicine, University of Bologna, Bologna, Italy
Andrea Farioli, Department of Internal Medicine, Geriatrics and Nephrology, University of Bologna, Bologna, Italy
Francesco Violante, Department of Internal Medicine, Geriatrics and Nephrology, University of Bologna, Bologna, Italy
Introduction
To evaluate the risk of musculoskeletal disorders to the hand, wrist and forearm, the American Conference of Governmental Industrial Hygienists (ACGIH) proposed a Threshold Limit Value (TLV) based on Hand Activity Level (HAL) and normalized Peak Force (PF). We applied the ACGIH TLV in OCTOPUS, a large occupational cohort study on carpal tunnel syndrome (CTS).

Methods
Different groups of industrial and service workers (performing medium/long-cycle tasks) were followed in 2000-2003. We estimated HAL and PF for each job task and we classified subjects with respect to Action Limit (AL) and TLV. Case definition was based on self-reported symptoms of CTS according to Consensus Criteria for the Classification of CTS in Epidemiologic Studies. We conducted Poisson regression analyses (adjusted for age, gender and personal characteristics) to estimate incidence rate ratios (IRR) of CTS symptoms.

Results
We studied 2,472 workers (mean age 37.5, SD 9.4; females 62.0%). ACGIH TLV predicted symptoms onset [IRR between AL and TLV 2.33 (95%CI 1.76-3.07); above TLV 3.07 (95%CI 2.33-4.05)]; however, when analyzed separately, HAL was the main determinant [IRR for subjects in the highest tertile 2.58 (95%CI 1.46-4.56)] and PF had a minor role [IRR for subjects in the highest tertile 1.68 (95%CI 1.05-2.69)]. The absolute increase in incidence of CTS symptoms was much higher in females (adjusted incidence below AL 4.9/100pyears, 95%CI 3.9-6.3; above TLV 17.7/100pyears, 95%CI 12.8-22.7) than in males [(adjusted incidence below AL 2.1/100pyears (95%CI 1.2-3.6); above the TLV 3.8/100pyears (95%CI 2.1-6.7)].

Discussion
We found a dose-response relationship between ACGIH TLV and risk of CTS symptoms, mainly determined by HAL. The incidence of symptoms attributable to occupational exposures was much greater among females; this element, alongside with the increase in risk observed for workers exposed between AL and TLV, support the hypothesis that gender-specific exposure limits should be considered to decrease the burden of CTS.

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