The frequency of carpal tunnel syndrome in computer users at a medical facility

To the Editor:

The article by Stevens et al.1 contains a serious logical flaw that appears to have escaped your reviewers’ notice.

The authors argue that heavy use of computer keyboards does not place individuals at risk for developing carpal tunnel syndrome (CTS). To support this view, they argue that the rate of CTS observed in this population is only slightly higher than that observed in the general population. The authors cite a number of other studies that provide estimates of the frequency of CTS in the general population to support this claim.

Unfortunately, the authors do not provide any indication of the causes of general population CTS cited in these other reports. Presumably CTS does not simply appear out of nowhere in the general population—indeed, it is probably tied to the type of work that people do. Perhaps these general population cases were even tied to keyboard use! With the lack of information provided by the authors, it is impossible to say. Nevertheless, this disconnect renders their conclusions about the lack of a causal relation between keyboard use and CTS suspect.

Simply put, the fact that CTS incidence rates are the same in keyboard users as in the general population not only does NOT prove that keyboard use is a causal factor, it may very well offer strong evidence that it is! Specifically, if CTS in the general population is caused by work-related factors (and again, the authors don’t tell us what it is due to), then the slightly higher rate seen among keyboard users suggests that their job is at least as much a causal factor as whatever is causing problems in the general working population.

Had I been a reviewer of this manuscript I would have advised against publishing it without more detail concerning the factors …