Carpal tunnel syndrome incidence in a general population.
To determine the incidence of carpal tunnel syndrome (CTS) in a general population of a restricted area in the middle part of Italy. Prospective study to identify cases of CTS, newly diagnosed on the basis of clinical symptoms and delay in distal conduction velocity of the median nerve. In the 8-year period from 1991 to 1998, cases were identified by electromyographic services in the Siena area of Local Health District No. 7 of Tuscany (Italy). This area has a population of 120,000. In the 8-year period, 3,142 cases (79.7% women and 20.3% men; mean age, 55 years; range, 13 to 97 years) were identified. The mean annual crude incidence was 329 cases per 100,000 person-years, and the standardized incidence was 276. The sex-specific incidences were 139 for men and 506 for women. The mean annual incidence for men increased moderately but significantly during the study period, whereas that for women remained constant. The age-specific incidence for women increased gradually with age, reaching a peak between 50 and 59 years, after which it declined. In men, there was a bimodal distribution with peaks between 50 and 59 years and between 70 and 79 years. Rural and industrial areas had higher crude and age- and sex-specific incidences than did urban areas. The incidence in the Siena area is about threefold that reported in the Rochester area (Minnesota) and is similar to that of Marshfield (Wisconsin). The different results with respect to US reports may depend on case inclusion criteria and occupational activities of the population at risk.