Cornell University Ergonomics Web


According to media reports of a recent research studies by researchers in Denmark and those at the Mayo clinic in Scottsdale, Arizona, there is no association between computer use and carpal tunnel syndrome (CTS) . This report apparently contradicts widely held assumptions about the causes of computer-related injuries, so what's the truth?

What is Carpal Tunnel Syndrome? 

CTS is caused by compression of the median nerve as this passes through the carpal tunnel, a narrow channel in the wrist between the carpal bones of the wrist (tunnel roof) and the transverse carpal ligament (tunnel floor). Sustained compression of the median nerve disrupts the axonal transport of fluids and this causes damage to the nerve fibers, a process termed neuropathy. The median nerve is a mixed nerve with both sensory and motor fibers. The sensory fibers are those first affected, and intermittent paresthesia (numbness, tingling) of the thumb and first two fingers often signifies the early stages of CTS.

The Danish Study [1]

A questionnaire follow-up survey of 5,658 Danish workers was conducted one year after a baseline survey had been completed by 6943 workers. The survey collected self-report data on carpal tunnel syndrome symptoms. The prevalence of self-reported symptoms at the baseline survey was 10.9%. The incidence of new or worsened CTS symptoms at the 1-year survey was 5.5%. The prevalence of median nerve symptoms at 1-year was 1.2%. At the baseline, there was no association of psychosocial factors (high work demands, high job pressure, low job control, low social support) or physical factors and possible CTS. At the 1-year follow-up, the average computer use for men was 8 hours per week and for women was 9.3 hours per week and there was no significant association between keyboard use and possible CTS. At the 1-year follow-up, the average mouse use for men was 12.5 hours per week and for women was 14.7 hours per week and there was a  significant association between mouse use >20 hours per week and possible CTS. The authors concluded that computer use is unrelated to carpal tunnel syndrome.

Limitations with the Danish Study 

The fact that the Danish workers only used their keyboard for an average of 8-9 hours per week is a serious limitation. This can hardly be considered hardly intensive keyboard use, especially  by US standards where workers may be keying intensively for >30 hours per week. A

The Danish workers  did make more intensive use of a mouse for an average of 12-15 hours per week, and that the authors noted a significant association between intensive mouse use and possible CTS, with an odds ratio of 3 for possible CTS for workers with  >20 hours per week of mouse use. Other recent Danish work has also found that mouse use increases musculoskeletal injury risks.[2] Both Danish studies found that there was no association of psychosocial factors with injury risks. Contrary to Andersen et al.'s conclusions, both Danish studies present results suggesting that computer use is related to musculoskeletal injuries, such as possible CTS.

It may be unwise to generalize from computer workers in Denmark to those the USA. In Denmark, by law the work week is shorter and ergonomic working conditions are more regulated than in the USA. Providing a high quality working environment is a legal requirement in Denmark and worker awareness of ergonomics and the use of ergonomically designed furniture is widespread. Ergonomists have always maintained that computer use need not increase musculoskeletal risks if the workstation is ergonomically designed, and Andersen et al.'s study may partly be confirming this. Unfortunately, unlike Denmark, many US companies still fail to grasp the benefits of ergonomics, and ergonomically designed workstations remain the exception rather than the rule.

The Mayo Clinic Study [3]

A questionnaire survey of workers using computers at the Mayo clinic in Scottsdale, Arizona, was conducted. Complete data were received for a sample of 257 respondents (81.8% return rate). Some 95% of respondents were women. Of these, 181 employees (70.4%) reported no symptoms of CTS, but 70 employees (29.6%) did report hand paresthesia. From subsequent interview, 27 employees (10.5%) were classified as having CTS. Of these employees, 9 people (3.5%) met a clinical definition of CTS and showed changes in nerve conduction velocity. Steven et al. conclude that this prevalence of CTS is comparable to that for CTS among the general population, and therefore computer use cannot be associated with the development of this syndrome.

Limitations with the Mayo Clinic Study 

Before finally concluding that there is no association between CTS and computer use it is worth considering the following issues:

What does it all mean? 

Does computer use cause CTS? Ergonomists have never claimed that computer use is the sole cause of CTS. Ergonomics research shows that computer users often adopt poor wrist postures, and working in deviated postures is thought to increase the risks of injury. Ergonomists have always maintained that computers can be used safely providing the user works in a neutral posture. No assessment of user posture was made in the Mayo study.

What the Mayo study has shown is the prevalence of CTS, characterized by median nerve latency, among women working at the Scottsdale facility of the Mayo clinic. In that respect the study is fine. However, the authors then proceed to compare their results to prevalence data for a Dutch and a Swedish study, and because the overall percentages look similar they assert that computer use has not played any role in the Mayo workplace. That assertion is flawed for the reasons described above. Thee media have reported this study as "proving" that there is no association between computer use and carpal tunnel syndrome, and that assumption too is flawed for the reasons already noted.

The Mayo study doesn't provide any definitive answer on the association between computer use and CTS, and the truthful answer is that we still don't know precisely what this is. What we do know is that computer-use often is associated with a variety of musculoskeletal complaints, and these adversely affect performance at work. We also know that musculoskeletal complaints can be successfully prevented by working at a computer in a neutral posture.

What the Danish study shows is that intensive mouse use is related to possible CTS, and other variables, such as psychosocial factors, are unrelated.

For information on how to arrange a computer workstation for neutral posture working see the adult workstation guide and the web site.


  1. Andersen, J.H., Thomsen, J.F., Overgaaard, E., Lassen, C.F., Brandt, L.P.A., Vilstrup, I., Kryger, A.I. and Mikkelsen, S. (2003) Computer use and carpal tunnel syndrome: A 1-year follow-up study, JAMA, 289(22): 2963-2969.
  2. Jensen, C., Finsen, L., Søgaard, K., and Christensen, H. (2002) Musculoskeletal symptoms and duration of computer and mouse use, Int. J. Industrial Ergonomics, 30(4-5) , 265-275.
  3. Stevens, J.C., Witt, J.C., Smith, B.E. and A.L. Weaver (2001) The frequency of carpal tunnel syndrome in computer users at a medical facility, Neurology, 56, 1568-1570. 
  4. De Krom M.C., Knipschild, P.G., Kester, A.D., Thijs, C.T., Boskkooi, P.F. and F. Spaans (1992) Carpal tunnel syndrome: prevalence in the general population. J. Clin. Epidemiol. 45, 373-375. 
  5. Atroshi, I., Gummessons, C., Johnsson, R., Ornstein, E., Ranstam, J. and Rosén, I. (1999) JAMA, 282 (2) 153-158. 
  6. Nordstrom, D. L., F. DeStefano, et al. (1998). Incidence of diagnosed carpal tunnel syndrome in a general population. Epidemiology 9 (3): 342-5.
  7. Franklin, G. M., J. Haug, et al. (1991). "Occupational carpal tunnel syndrome in Washington State, 1984-1988." Am J Public Health 81(6): 741-6.
  8. Tanaka, S., D. K. Wild, et al. (1995). "Prevalence and work-relatedness of self-reported carpal tunnel syndrome among U.S. workers: analysis of the Occupational Health Supplement data of 1988 National Health Interview Survey [see comments]." Am J Ind Med 27(4): 451-70.

Hit Counter