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Context Computer use is increasingly common among many working populations, and concern exists about possible adverse effects of computer use, such as carpal tunnel syndrome (CTS).Objectives To estimate the prevalence and incidence of possible CTS and to evaluate the contribution of use of mouse devices and keyboards to the risk of possible CTS.Design and Setting A 1-year follow-up study with questionnaires conducted in 2000 and 2001 at 3500 workplaces in Denmark, followed on each of the 2 occasions by a clinical interview on symptom distribution and frequency.Participants The questionnaire was sent to 9480 members of a trade union, with an initial response rate of 73% (n=6943), and 82% (n=5658) at follow-up. Main Outcome MeasuresAt baseline, there were 3 outcome measures: tingling/ numbness in the right hand once a week or more as reported in the questionnaire; tingling, numbness, and pain in the median nerve in the right hand confirmed by clinical interview; and tingling, numbness, and pain in the median nerve in the right hand at night confirmed by clinical interview. At 1 year of follow-up the main outcome of interest was onset of symptoms among participants who had no or minor symptoms at baseline. ResultsThe overall self-reported prevalence of tingling/numbness in the right hand at baseline was 10.9%. The interview confirmed that prevalence of tingling/ numbness in the median nerve was 4.8%, of which about one third, corresponding to a prevalence of 1.4%, experienced symptoms at night. Onset of new symptoms in the 1-year follow-up was 5.5%. In the cross-sectional comparisons and in the follow-up analyses, there was an association between use of a mouse device for more than 20 h/wk and risk of possible CTS but no statistically significant association with keyboard use. ConclusionsThe occurrence of possible CTS in the right hand was low. The study emphasizes that computer use does not pose a severe occupational hazard for developing symptoms of CTS.

Aims: To determine the occurrence of pain conditions and disorders in the forearm and to evaluate risk factors for forearm pain in a cohort of computer workers. Methods: A total of 6943 participants with a wide range of computer use and work tasks were studied. At baseline and at one year follow up participants completed a questionnaire. Participants with relevant forearm symptoms were offered a clinical examination. Symptom cases and clinical cases were defined on the basis of self reported pain score and palpation tenderness in the muscles of the forearm. Results: The seven days prevalence of moderate to severe forearm pain was 4.3%. Sixteen of 296 symptom cases met criteria for being a clinical forearm case, and 12 had signs of potential nerve entrapment. One year incidence of reported symptom cases was 1.3%; no subjects developed new signs of nerve entrapment. Increased risk of new forearm pain was associated with use of a mouse device for more than 30 hours per week, and with keyboard use more than 15 hours per week. High job demands and time pressure at baseline were risk factors for onset of forearm pain; women had a twofold increased risk of developing forearm pain. Self reported ergonomic workplace factors at baseline did not predict future forearm pain. Conclusion: Intensive use of a mouse device, and to a lesser extent keyboard usage, were the main risk factors for forearm pain. The occurrence of clinical disorders was low, suggesting that computer use is not commonly associated with any severe occupational hazard to the forearm.

Detailed examination of self-reported exposures showed that mouse and keyboard time predicted elbow and wrist/hand pain from low exposure levels without a threshold effect, but mouse and keyboard time were not predictors of clinical conditions.

Background: Computer use may have an adverse effect on musculoskeletal outcomes. This study assessed the risk of neck and shoulder pain associated with objectively recorded professional computer use. Methods: A computer programme was used to collect data on mouse and keyboard usage and weekly reports of neck and shoulder pain among 2146 technical assistants. Questionnaires were also completed at baseline and at 12 months. The three outcome measures were: (1) acute pain (measured as weekly pain); (2) prolonged pain (no or minor pain in the neck and shoulder region over four consecutive weeks followed by three consecutive weeks with a high pain score); and (3) chronic pain (reported pain or discomfort lasting more than 30 days and ''quite a lot of trouble'' during the past 12 months). Results: Risk for acute neck pain and shoulder pain increased linearly by 4% and 10%, respectively, for each quartile increase in weekly mouse usage time. Mouse and keyboard usage time did not predict the onset of prolonged or chronic pain in the neck or shoulder. Women had higher risks for neck and shoulder pain. Number of keystrokes and mouse clicks, length of the average activity period, and micro-pauses did not influence reports of acute or prolonged pain. A few psychosocial factors predicted the risk of prolonged pain. Conclusions: Most computer workers have no or minor neck and shoulder pain, few experience prolonged pain, and even fewer, chronic neck and shoulder pain. Moreover, there seems to be no relationship between computer use and prolonged and chronic neck and shoulder pain.Musculoskeletal complaints have been regarded as an adverse effect of computer use, and numerous studies have been conducted, most of them pointing to an association between neck and upper extremity pain and duration of computer use. 1-6Most of these associations have been based on cross-sectional comparisons of self-reported computer, keyboard or mouse use and self-reported pain complaints. 7 A minority of studies which have used clinical outcome measures have either found too few cases with traditional medical diagnoses to perform meaningful analyses or have used diagnostics that were controversial.3 6 Recently, methodologies for assessing work activity during computer use have been evaluated, and activitybased recordings of computer use seem to be reliable and in agreement with measures obtained by observational techniques. [8][9][10][11] A recent review called for future studies to improve our understanding of safe levels of computer use by measuring the duration of computer use in a more objective way, differentiating between mouse and keyboard use.12 In a substudy of the NUDATA (Neck and Upper extremity Disorders Among Technical Assistants) study we found that even though self-reports of mouse and keyboard use were correlated with objective recordings, participants overestimated their mouse use two to three times, and their keyboard usage up to six times when compared with the recordings. 13 The aim of this study was to examine if obje...