The computer is now ubiquitous in our workplaces. But does all that keyboarding, typing, mouse clicking and mouse dragging cause or contribute to Carpal Tunnel Syndrome (“CTS”)? Given the prevalence of both occupational computer usage and diagnosed cases of CTS, this topic generates a lot of debate. However, “popular belief” notwithstanding, the scientific data developed to date does not show an association between the two.
At least that is the conclusion reached by a group of French researchers who undertook a meta-analysis (“conducting research about research”) of various epidemiological studies conducted on this subject over a twenty-year period. Their results and analysis are published in the February 2014 edition of JOEM, Is Carpal Tunnel Syndrome Related to Work Exposure at Work? A Review and Meta-Analysis. In short, the review and meta-analysis found that while some “particular work circumstances” may be associated with CTS, “it was not possible to show an association between computer use and CTS.”
It is axiomatic that occupational computer use has increased dramatically over the past twenty years; it is equally true that CTS results in reduced productivity and increased healthcare costs. So the importance of knowing whether there is an association between the two is evident. However, although various studies and reviews have been undertaken over the past twenty years on this precise issue, no clear consensus or conclusion had emerged. In an effort to bring more sharply into focus the picture painted by the totality of the data collected thus far, this group of researchers decided to undertake the first quantitative analysis of the existing body of work.
Review and Meta-Analysis Methodology and Results
Four databases (PubMed, Embase, Web of Science and the French Public Health Database) were searched for relevant studies conducted during the 1992 through 2012 timeframe. This originally yielded 77 studies, a number which was further reduced by including only those studies which (a) used a control group; (b) confirmed a CTS diagnosis by electrophysiological investigation or hand surgeons; and (c) assessed the association between computer use and CTS with blind-reviewing. Using these parameters, the final tally of studies included in the meta-review totaled 6 – 3 from the United States, 1 from Denmark, 1 from Sweden and 1 from Taiwan. The meta-analysis reviewed all the raw data collected by these studies. This included the type of computer use (for example keyboard or mouse use), the number of hours worked and the ergonomic conditions at work. Other factors included in the analysis were the type of study from which the data was being extracted (i.e. whether it was a longitudinal or cross-sectional study), whether the workplace activity was independently assessed or self-reported, the number of people in the study, the number of diagnosed CTS cases, and the criteria used in each study to calculate the odds-ratio (“OR”).
Based on the data in the reviewed studies, the meta-analysis reached its conclusion that there was no evidence of an association between computer work and CTS. The meta-OR (“the combined OR measuring the association between the exposure and outcome”) was “slightly” higher than 1 but not “statistically significant.” Specifically, the meta-OR for computer use was 1.67, for keyboarding was 1.11 and for mouse usage was 1.94.
Review and Meta-Analysis Limitations
Nevertheless, some longitudinal studies have found that complaints of pain are quite common amongst computer users. So what is the cause of the apparent contradiction? The meta-analysis suggests several reasons, one of the most prominent being the complexity involved in evaluating computer work exposure. For example, some of the data reviewed indicated that when evaluating finger, wrist and forearm positions, there might be a difference between keyboard use and typing, and that of mouse use. Another possible variable is whether the hand is “static” on the mouse or whether the mouse is being dragged or clicked. According to the meta-analysis, the data suggests that “mean carpal tunnel pressure” is higher for the latter. Also further complicating the picture are differences in work situations and tasks assigned. The meta-analysis notes that office workers, graphic artists and computer professionals, working in different environments around the world, all experience different types of computer usage exposure.
Besides differences in computer usage mechanics, variables in hours worked and ergonomic conditions may impact the OR. For example, one study reviewed indicated that symptoms increased when working more than 12 hours per day. As to ergonomic conditions, while these “may be associated with an increased CTS risk, requiring intervention” the risk is “not sufficient to claim occupational compensation for computer use.” Moreover, while the meta-analysis suggests the possibility of an increased CTS risk for prolonged mouse use, coupled with ergonomic “errors”, it does not state how much mouse use is considered “prolonged” nor identify the perceived ergonomic “errors”.
Finally, heterogeneous study methods also impact the results obtained and limit the quantitative meta-analysis. These include differences in the definition of what computer work, whether the computer usage was observed or self-reported and whether the study was cross-sectional or longitudinal. The meta-analysis itself was limited by the methodology used to select the articles and collect the data, the lack of uniformity of results in the studies under review and the small number of studies chosen for review.
Despite these limitations, the meta-analysis provides a good window through which to view the current available data on this important issue—and the data shows no association between occupational computer usage and CTS. However, the articulated limitations, which were acknowledged within the meta-analysis, suggest that further debate and research is likely on this important topic.
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