Estimating the prevalence of delayed median nerve conduction in the general population.

The objectives of this study were to determine the point prevalence of neurophysiologically defined median nerve compression and associated carpal tunnel syndrome in a random sample of the general population. The design was a two-stage screening study: (i) a cross-sectional survey to estimate the point prevalence of current hand symptoms; (ii) nerve conduction testing of the median nerve in weighted samples of the survey respondents. The target study population was a random sample of 1000 adults aged between 18 and 75 yr registered with a family practice in the UK. A mailed questionnaire enquired about hand symptoms on the day and included various demographic questions. Weighted random samples were taken based on the hand symptoms reported, and the subjects were invited to attend for motor and sensory median nerve conduction testing. A neurophysiological diagnosis of median nerve compression was made based on a number of different cut-offs using published criteria. Of those receiving a questionnaire, 79% responded. A total of 250 responders were invited to attend for nerve conduction testing, of whom 155 (62%) attended. Non-response to the questionnaire and non-attendance for nerve conduction testing may have biased the prevalence estimates. After adjustment for such biases, a prevalence estimate of between 7 and 16% was obtained, varying with the different cut-offs used to define delayed median nerve conduction. Subjects over 54 yr of age had a higher prevalence than younger participants. There was no difference in prevalence estimates between men and women. The conclusion reached was that carpal tunnel syndrome, as assessed by delayed median nerve conduction, is common in the general population.