Carpal Tunnel Syndrome Not Caused by Keyboard Use
It is estimated that more than 25,000 people miss work each year as a result of
In a study published in the June 11, 2003 issue of the Journal of the American Medical Association , researchers found that using a computer keyboard repetitively was not associated with developing CTS symptoms. Interestingly, time spent using a computer mouse did increase the risk of having CTS symptoms among participants in this study.
About the Study
Researchers in Denmark used about 7,000 men and women from a study that examined the relationship between computer use and musculoskeletal symptoms of the upper body. The participants were members of the Danish Association of Professional Technicians trade union. The union consisted of a wide variety of occupational groups, including technical assistants (draftsmen), machine technicians, and people who performed an assortment of drawing, administrative, graphical, and office-based tasks. Because of this variety, there was a wide distribution of both mouse and keyboard use.
At the start of this study and again one year later, researchers asked the participants if they had tingling, numbness, or pain in their right hand. People who reported having these symptoms attended a clinical examination to confirm that their symptoms were consistent with CTS. The participants were also asked about time spent using a computer mouse, time spent using a keyboard, work-related physical factors (i.e., workstation setup), work-related psychosocial factors (i.e., job pressures), and personal characteristics (i.e., weight, age, social network, etc.).
When the study began, 4.8% of the participants had confirmed symptoms of CTS, of which one-third (1.4% of the entire group) also experienced symptoms at night—a common effect of CTS since flexing the wrists during sleep puts extra pressure on the median nerve.
At the start of the study, time spent using a mouse was associated with increased risk of having CTS symptoms. Dissatisfaction with physical workspace (i.e., mouse and keyboard position, wrist support, adjustability of desk chair) also significantly increased the risk of having CTS symptoms. The number of hours the participants spent using a keyboard, however, did not increase the risk of having CTS symptoms.
After one year, 5.5% of the participants reported having new or worsening symptoms. The onset of CTS symptoms was linked with using a mouse for 20 or more hours a week, but time spent using a keyboard was still not associated with CTS symptoms.
There are limitations to these findings. Because the participants in this study were exposed to recent media reports of “mouse-related disorders” and “mouse arm,” some who reported CTS symptoms might have unintentionally over-reported their time spent using a mouse because they assumed their symptoms were caused by using a mouse. This may account for the link between mouse use and CTS symptoms in this study.
How Does This Affect You?
This study supports the notion that repetitive keyboard use is probably not an important risk factor for CTS. More likely causes of CTS include a genetically small carpal tunnel, injury to the wrist, pregnancy, and medical problems.
Still, uncomfortable work environments that disrupt your natural posture can wear on your arms, wrists, hands, fingers, neck, back, and shoulders. Many people who work at a computer regularly develop writer’s cramp, which causes pain in the fingers, wrist, and forearm. To help prevent writer’s cramp and other ailments associated with computer use, the National Institutes of Health (NIH) recommends that people make the following adjustments to their work environments:
- Adjust the height of your keyboard so that your shoulders are relaxed and your arms rest comfortably at your sides.
- Keep your keyboard close to you so that you don’t have to reach for it excessively.
- Make sure your keyboard is positioned so that your arms are parallel to the floor, with a 90° bend in your elbow.
- Place your mouse at the same height as your keyboard, adjacent to the keyboard.
- Avoid reaching for the keyboard and mouse excessively, if at all possible.
- Focus on keeping your wrist relaxed, not flexed or extended.
- Rest your hands in your lap—not on the mouse—when you aren’t using the keyboard or mouse.
Since untreated CTS may eventually lead to permanent nerve damage, it is important to see your physician for a full evaluation if you’re are having persistent symptoms.
University of California, Los Angeles
American Academy of Orthopaedic Surgeons
Anderson JH, Thomsen JF, Overgaard E, et al. Computer use and carpal tunnel syndrome: a one-year follow-up study. JAMA. 2003;289:2963-2969.
Bureau of Labor Statistics website
Available at: http://www.bls.gov/
Accessed on June 10, 2003
National Institutes of Neurological Disorders and Stroke website
Available at: http://www.ninds.nih.gov/
Accessed on June 9, 2003
Stevens JC, Witt JC, Smith BE, Weaver AL. The frequency of carpal tunnel syndrome in computer users at a medical facility. Neurology . 2001;65:1568-1570.
National Institutes of Health website
Available at: http://www.nih.gov/
Accessed on June 9, 2003
Last reviewed June 12, 2003 by
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