A cohort study on Raynaud's phenomenon in workers exposed to low level hand-arm vibration

To clarify the incidence of Raynaud's phenomenon among workers exposed to low level hand-arm vibration for a long time, a sample cohort of workers mainly operating a bush cleaner (the vibration level was 2-4 m/s(2)rms) were followed up for a period of 20 yr. The sample cohort consisted of 331 male workers mainly working at maintaining public roads or afforesting and gardening on a farm. The examination was based on questionnaires used in special medical examinations for vibration syndrome from 1977 to 1996. Raynaud's phenomenon was observed in II subjects. The accumulative occurrence rate increased linearly in the case of more than 11 operating years. The mean number of operating years at the occurrence of Raynaud's phenomenon was 11.7 +/- 7.1 yr. The mean total operating time at the occurrence of Raynaud's phenomenon was 3,756 h on the geometric average. Stockholm Workshop scale classified 1 subject as Stage 1 (mild), 4 subjects Stage 2 (moderate) and 6 subjects Stage 3 (severe). By the person-year method, the incidence of Raynaud's phenomenon was 4.48 per 1000 person-year. These findings show that the number of operating years for a bush cleaner should be considered to prevent Raynaud's phenomenon, even though the hand-arm vibration level is low.