Carpal tunnel syndrome and keyboard use at work: a population-based study

OBJECTIVE: To investigate the relationship between carpal tunnel syndrome (CTS) and keyboard use at work in a general population. METHODS: A health status questionnaire was mailed to 2,465 persons of working age (25-65 years) who were randomly selected from the general population of a representative region of Sweden. The questionnaire required the subjects to provide information about the presence and severity of pain, numbness and tingling in each body region, employment history, and work activities, including average time spent using a keyboard during a usual working day. Those reporting recurrent hand numbness or tingling in the median nerve distribution were asked to undergo a physical examination and nerve conduction testing. The prevalence of CTS, defined as symptoms plus abnormal results on nerve conduction tests, was compared between groups of subjects that differed in their intensity of keyboard use, adjusting for age, sex, body mass index, and smoking status. RESULTS: Eighty-two percent responded to the questionnaire, and 80% of all symptomatic persons attended the examinations. Persons who had reported intensive keyboard use on the questionnaire were significantly less likely to be diagnosed as having CTS than were those who had reported little keyboard use, with a prevalence that increased from 2.6% in the highest keyboard use group (> or = 4 hours/day), to 2.9% in the moderate use group (1 to <4 hours/day), 4.9% in the low use group (<1 hour/day), and 5.2% in the no keyboard use at work group (P for trend = 0.032). Using > or = 1 hour/day to designate high keyboard use and <1 hour/day to designate low keyboard use, the prevalence ratio of CTS in the groups with high to low keyboard use was 0.55 (95% confidence interval 0.32, 0.96). CONCLUSION: Intensive keyboard use appears to be associated with a lower risk of CTS.