This is Part 1 of a two-part series
June 11, 2001 -- Office workers can "breathe a sigh of relief," according to a Mayo Clinic researcher. Contrary to popular belief, a new study shows that using a computer doesn't appear to increase the risk of developing carpal tunnel syndrome. The study appears in today's issue of the journal Neurology.
"The popular thought is that computer use confers a risk of carpal tunnel syndrome. We were expecting to find an increased risk, and when we didn't, we were surprised," author J. Clarke Stevens, MD, tell WebMD.
"We basically looked at people who used the computer keyboard heavily -- that is between 6-7 hours a day -- to find out how many of those people had carpal tunnel syndrome, and we found ... that this heavy computer keyboard use did not increase the risk of carpal tunnel," says Stevens, a neurologist at the Mayo Clinic in Rochester, Minn.
The carpal tunnel is a bone-and-ligament passageway between the forearm and the hand, at the wrist. The median nerve, which supplies feeling to the thumb, index and ring fingers, and the tendons that bend the fingers, passes through this tunnel.
Usually, carpal tunnel syndrome is considered an inflammatory disorder caused by repetitive stress, physical injury, or other conditions that cause the tissues around the median nerve to swell. The swelling compresses the median nerve fibers, which in turn interferes with the transmission of nerve signals through the carpal tunnel. The result is pain, numbness, and tingling in the wrist, hand, and fingers, except the pinkie finger, which is not affected by the median nerve.
In the study, Stevens and his colleagues contacted more than 250 Mayo Clinic employees who used computers an average of six hours a day for their jobs. Approximately 30% said they had experienced numbness or pins-and-needles in their hands, but only 27 met the criteria for a diagnosis of the syndrome.
Nerve studies to confirm the diagnosis, however, found that only nine people actually had carpal tunnel syndrome. That's 3.5% of the original "heavy" computer users studied -- a percentage similar to that found in the general population.
Additionally, those with carpal tunnel were not any different -- in terms of type of occupation, years on the job, number of hours on the computer per day -- from those without the syndrome, leading the researchers to conclude that using a computer "heavily" does not enhance the risk of carpal tunnel syndrome.
"It has been known that certain occupations outside of the office -- for example, using jack hammers, working in the meat packing industry, working in factories, where, thousands of times a day, a single repetitive action is done using the hand and wrist -- do increase the risk of carpal tunnel syndrome, and ... people thought that perhaps computer keyboard use is a different kind of repetitive motion activity and, therefore, also increases the risk," says Stevens. "But this study would suggest that does not seem to be the case."
Richard Olney, MD, a professor of clinical neurology at the University of California, San Francisco agrees, wrote an editorial to accompany the Neurology study. He suggests that high-force repetitive activity, like working in a factory or lumber mill, is a bigger culprit in carpal tunnel syndrome than the repetitive motion of using a computer keyboard.
"I think the study highlights that we don't have as good data for less-forceful repetitive activity," Olney tells WebMD.
So why has the incidence of carpal tunnel syndrome gone up at the same time as widespread computer usage?
"Perhaps the reason ... is not because of computer keyboard use, but because people are more aware of the symptoms and medical science has advanced with new diagnostic techniques to the point where more and more people are being identified who were missed previously," says Stevens.
That is not to say that using a computer can't and doesn't lead to aches and pains. This study suggests instead that it doesn't necessarily lead to carpal tunnel syndrome.
"In our study, we found that about 60% of those people at one time or another in the previous year had had aches and pains involving the neck, shoulder, arm, wrist, or hand that they associated with their use of the keyboard," says Stevens. "It does mean that using the computer keyboard is not without some health risk, but it is not carpal tunnel syndrome ... ."
"In some people with hand pain, it is more of a tendonitis," says Olney, referring to another very common diagnosis. "And it might well be that tendonitis does have more to do with the hand discomfort that develops with keyboard usage."
Tendonitis, Olney says, is caused by inflammation of the tendons or the tissue, as opposed to pain from compression on the median nerve. And for that reason, patients shouldn't rush to have surgery when, in the case of tendonitis, rest and readily available NSAIDs, or nonsteroidal anti-inflammatory drugs like aspirin, can relieve the condition.
The findings have other implications as well.
"No one has yet demonstrated that ergonomic measures are really effective in preventing [carpal tunnel syndrome]," says Olney. "You would think that if improper computer use causes carpal tunnel, then if companies are made to spend hundreds of thousands of dollars to institute ergonomic measures to help prevent it, that they ought to see some economic benefit of that, but it is not clear that is the case."
Both Stevens and Olney agree that more research in larger groups of heavy computer keyboard users is needed. "This surprising, ground-breaking data suggest that perhaps other centers with larger numbers of computer users may shed further light on this important issue in the work place," says Stevens.