A follow up study on the consequences of VWF patients in workers using chain saws in Japanese National Forests

Abstract

The authors carried out more than 20 yr of follow up studies of vibration- induced white finger (VWF) from the time the use of chain saws ceased. A total of 496 workers who were affected by VWF during the period 1955-82 were followed up to observe the consequences of VWF. These subjects were selected from a total of 1,586 chain saw operators who had used chain saws as a professional operator during some of the years from 1955 to 1982 in the national forests on Kyushu Island, Japan. In 1997 the authors had verified the current status and the course of VWF by direct interviews. A life table Product Limit method analysis of VWF prevalence was carried out to describe the consequences of VWF from the time the use of chain saws ceased. Out of the total number of subjects it was possible to follow 488 workers (98.4%) to ascertain their current states. Fourhundred and eighty-one (98.6%) workers had retired and of these 124 (25.4%) had died. The rate of prevalence of VWF fell continuously after the use of chain saw ceased from 29.3% to a final value of 18.8% after more than 20 years' observation. It was observed that the percentage prevalence depended significantly on the severity: 87% for the subjects with stage 3, 53% for stage 2 and 17% for stage 1. The time course of the rate of recovery from moderate VWF differed from that of severe VWF. Peripheral neuropathies and sympathetic disturbances were predominantly observed in severe stage VWF cases in pathophysiological examinations.