The onset of carpal tunnel syndrome (CTS) was three times greater among subjects who performed tasks considered “biomechanically unacceptable” through analysis using the American Conference of Governmental Industrial Hygienists (ACGIH) hand activity level (HAL) methodology. In a one year, prospective, cohort study by Violante et al. involving 2,092 workers, it was also determined that volunteers whose tasks were HAL classified as “borderline overload” had a 1.5-fold greater risk of CTS incidence. The authors suggest the data may indicate a dose response relationship.
Over the course of the study, the incidence of CTS was 7.3%. Personal factors were also assessed. CTS incidence was found to be:
- Four times more likely in females
- Twice as likely among those with pathologies facilitating CTS onset
- Twice as likely among those with high alcohol consumption (greater than four drinks per day)
- Slightly increased among those who ever smoked cigarettes
There was no association between CTS incidence and combinations of BMI/wrist circumference. Light to moderate alcohol intake (two to six drinks per week) and being taller than average was seen as slightly protective.
When considering worse baseline to one year outcomes (becoming symptomatic/remaining symptomatic through the duration of the study):
- Females had a four-fold higher risk
- Subjects greater than 35 years of age were twice or more at risk
- Those performing “biomechanically unacceptable” tasks had a two-fold risk
- Overweight/obesity, pathological conditions facilitating CTS onset, cigarette smoking, and history of exposure to biomechanical overload demonstrated a slight relationship
Being taller than average was protective again.
As biomechanical exposure worsened, the risk of CTS among females increased. Little impact was seen among the overweight/obese group as biomechanical exposure worsened.
Study Design
Subjects
Blue collar employees were recruited at factories producing small appliances, large appliances, shoes, ceramic tiles, and underwear along with workers who were employed at nursery schools. Those who had a history of CTS surgery or underwent CTS surgery during the course of the study were excluded. Also, those who had a change in task exposure level were excluded. Among the final volunteer population of 2,092 workers, 65% were females.
Job Analysis
A list of tasks performed at each workplace was given to researchers and during a walk-through survey, representative examples of the identified activities were found. The ACGIH HAL analysis methodology (2006), a tool that focuses on hand exertion frequency, recovery time, percent duty time, and speed of motion was applied to the tasks. HAL is intended to be applied to mono-task jobs (work activity characterized by repeatedly performing a similar set of motions or exertions) that are done for four or more hours per day. The tool identifies three categories of task hand biomechanical demand:
- Unacceptable overloads
This article originally appeared in The Ergonomics Report™ on 2007-12-19.