Mayo Clinic study debunks possible link between heavy computer use and carpal tunnel syndrome

ROCHESTER, MINN. -- Surprising even the researchers themselves, a new study from Mayo Clinic found that heavy computer use, even up to seven hours per day, did not increase a person�s risk of carpal tunnel syndrome (CTS).

The results of the research, to be published in the June 12 issue of Neurology, indicate that only 10.5 percent of the study participants, all of whom used computers extensively, met clinical criteria for CTS. This incidence is similar to that found in the general population in past studies, according to the authors of Mayo Clinic�s manuscript.

"We had expected to find a much higher incidence of carpal tunnel syndrome in the heavy computer users in our study because it is a commonly held belief that computer use causes carpal tunnel syndrome," says J. Clarke Stevens, M.D., a neurologist at Mayo Clinic in Rochester, Minn., and lead author of the study. "The other finding was that among our cases of carpal tunnel syndrome, two-thirds of them had very mild carpal tunnel syndrome. Our study results were unexpected," said Dr. Stevens. Dr. Stevens formerly served as chair of the Department of Neurology at Mayo Clinic in Scottsdale, Ariz.

This is the first major study to consider the association between the syndrome and computer usage. "The findings are contrary to popular thought, but nobody has studied the problem carefully," says Dr. Stevens. "There has been very little formal study of carpal tunnel syndrome in computer users, and there is not much to find in the literature on this topic. We studied computer users because though there is a commonly held notion that using a computer causes CTS, there really have been few studies published that looked at this in a scientific way."

Dr. Stevens offers a message of relief for those who may have wondered about their risks of the so-called "office plague" due to long hours spent in front of a computer. "I�d like computer users to know that prolonged use of a computer does not seem to lead to carpal tunnel, at least not in our employees who used computers up to seven hours per day," says Dr. Stevens. Carpal tunnel syndrome is a common condition in the population, however, which means that some computer users will develop carpal tunnel syndrome.

Our study suggests, however, that the risk of developing the syndrome is not increased by working at a computer." Dr. Stevens indicates that though computer use may not be as highly associated with CTS as thought, it is associated with numerous other medical issues. "Carpal tunnel syndrome in computer users has been thought of as a repetitive motion disorder, and it has been assumed that computer use might cause carpal tunnel syndrome as part of such a disorder. People who use the computer do get a lot of other aches and pains in the neck, shoulder, arm and wrist, but most of them do not get carpal tunnel syndrome from using a computer."

As CTS is not the only ergonomics issue related to computer usage, a correct office setup still has great merit, according to Dr. Stevens. "The question arises as to whether ergonomically correct work stations are important," he says. "I think they continue to be very important, because there are a variety of aches and discomfort that can result from using a computer. A majority of the computer users in our study, including those without carpal tunnel syndrome, had experienced neck and upper extremity pain during the two years prior to the study. "What we are saying is that at least in our employees studied, computer use did not seem to increase the risk of getting carpal tunnel syndrome."

There are a variety of factors that do contribute to CTS, according to the study authors. "The major risk factors for developing carpal tunnel syndrome are being female and middle-aged," says Dr. Stevens. "There are many other causes of carpal tunnel syndrome, such as wrist trauma, diabetes, rheumatoid arthritis and pregnancy."

Repetitive motions in industries outside the office also have been linked to CTS, Dr. Stevens says. "There is certainly a whole variety of other jobs that are much more labor-intensive that we think might cause carpal tunnel syndrome, such as working in a meat packing plant or using a jackhammer," says Dr. Stevens. "There have been a number of studies of factory workers and people in packing plants that suggest that type of repetitive motion does seem to be associated with carpal tunnel syndrome."

Though the Mayo Clinic study authors consider their study to be an important first step in studying CTS and computer use, they would like to see further research conducted on the topic. "I think the study needs to be confirmed by other centers, possibly with a larger number of computer users," says Dr. Stevens. "I think more study is needed of this question."

The Mayo Clinic study was conducted with employees identified to be heavy computer users at Mayo Clinic in Scottsdale, Ariz. "We chose Mayo Clinic employees because we knew we could find out who were computer users at our medical center," says Dr. Stevens. "We have a large number of secretaries and people who do transcription and patient accounts billing. All of those are occupations that make heavy use of a computer, so we had our own ready-made study group right in our own facility."

The investigators sent surveys to 314 employees inquiring about hand numbness and sensations of "pins and needles," common symptoms of carpal tunnel syndrome. Of the 257 people who responded to the survey, those who indicated symptoms suggestive of carpal tunnel syndrome were invited to a clinical study unit for an interview and completion of further questionnaires. Unless these patients were clearly diagnosable with a condition other than CTS, they were tested for CTS via electromyogram (EMG), or a nerve conduction study. Only 27, or 10.5 percent, of the participants met clinical criteria for CTS, and in nine, or 3.5 percent, EMG confirmed the syndrome.

Though the researchers did not discover CTS in a high percentage of the participants, other conditions potentially linked to the office work environment were present in a larger number of participants.

"There were about 30 percent of our employees surveyed who had tingling of various sorts in the hand, but only 10.5 percent of them turned out to have carpal tunnel syndrome," says Dr. Stevens. "They had tingling from involvement of other nerves and a variety of symptoms that are likely not clinically significant. The vast majority of the people who had tingling in the hand but didn�t have carpal tunnel syndrome did not have any serious illness as far as we could determine. A few of them had what is called an �ulnar neuropathy,� which relates to another nerve in the hand, a few of them had pinched nerves in the neck, and a lot of them had rather mild and nondescript tingling that really did not mean much clinically."

For those who suspect that they may have problems in their hands, Dr. Stevens suggests consulting one�s family physician first, who would then make a decision about obtaining nerve conduction studies or perhaps refer to a hand clinic or surgeon for further evaluation.

Research suggests that one person in 10 will develop symptoms of CTS over a lifetime. CTS is a compression of the median nerve at the wrist, leading to numbness tingling and pain in the hand. The median nerve passes through the carpal tunnel at the wrist and into the palm where it sends branches that control feeling to the thumb, index, middle and part of the ring fingers.

Symptoms of CTS include tingling, pain or numbness in the hand and fingers. "It�s typically worse with reading a newspaper or book, talking on the phone or driving a car, and frequently it wakes people up in the middle of the night with tingling or pain in the hand," says Benn Smith, M.D., co-author of the study and neurologist at Mayo Clinic in Scottsdale, Ariz. "Very often, people obtain temporary relief by shaking the hand or rubbing it, causing the numbness and tingling to go away."

CTS is treated by wearing a splint at night to reduce waking up or by an injection of cortisone to reduce swelling. If these measures are not successful, carpal tunnel release surgery, which sections the tough transverse carpal ligament and relieves pressure on the median nerve, may be performed.

Other resources for journalists: Neurology web site: http://www.neurology.org. Neurology media relations contact: Kathy Stone, 651-695-2763. Biographical information on Dr. Stevens: http://www.mayo.edu:80/cerebro/division/cv_staff.stevens.html. Biographical information on Dr. Smith: http://www.mayo.edu:80/mcs/Medical_Staff/smith-be.html. Graphic and electronic version of news release: http://www.mayo.edu/news.

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