Recently, a study was published in the journal “Neurology” which purported to demonstrate that computer use was not associated with carpal tunnel syndrome and which received wide media attention. I would like to comment briefly on this study, because I fear that it may be interpreted as way obviating the vital need for an ergonomics standard in this country. This study, by JC Stevens et al is completely methodologically flawed in terms of its ability to determine causation.

The authors conducted a cross-sectional evaluation of the prevalence of  CTS among health care workers with self-reported use of computers at work. Possible or clinical CTS symptoms were identified among 27 of 257 participants. Twenty four of those people underwent the authors’ gold standard for CTS - electrodiagnostic studies; 3 people refused electrodiagnostic testing. The authors reported a prevalence of CTS of 3.5% ( a total of 9 cases) among the study population of 257 employees, and concluded that this demonstrated a lack of a connection between the occupational use of computers and CTS.

Unfortunately, the methodology employed in the study was not appropriate for the evaluation of causality. The primary weakness of the study is that it only included current workers – thus, any worker who was out of work because of CTS would not have been included in the study. This weakness – called the survivor effect – is particularly problematic in a study of a highly disabling disorder such as CTS. Because the number of cases in the population was only 9 -  if only 3 workers were out of work because of CTS, the authors would have failed to identify 33% of the cases. Additionally, as noted above, 3 of subjects with symptoms of possible CTS did not undergo the testing needed to determine if they indeed had CTS. Thus, there may have been 33% more cases than reported, even among current workers! There was no exposure assessment in the study. Finally, it is of note that the authors do, in fact, note that there was a significant proportion of computer workers with pain in the upper extremities. Thus, overall, this study is merely a description of the prevalence of CTS among a group with possible computer use.