Abstract
A retrospective longitudinal study was undertaken to evaluate the changes in the prevalence of vibration-induced white finger (VWF) during the period from 1955 to 1988 among a population of Japanese state forestry workers. Since the late 1970s, technical improvements in the engine and the introduction of devices to dampen vibration have reduced the acceleration of chain saw handles from 20 ms−2 rms to less than 3 ms−2 rms. During the study period, the peak prevalence rate was 30.9% in 1973 and 17.2% in 1988. The peak prevalence rate was 54.8%, found in the exposure cohort beginning in 1959–1960 and the peak incidence rate was 5.65 per 100 person year in 1965–1966. Beginning with the 1969–1970 exposure cohort, both the prevalence and the incidence rate decreased significantly. During the study period, prevalence rates were approximately 10, 20, 30 and 35% after 4, 6, 10 and 12 years of exposure, respectively. The latent interval for the development of VWF was 6.2 ± 3.9 years on average, and the duration of VWF was 13.1 ± 7.5 years on average through the 1988 observation period. The 1950 cohort group had a long latent interval and a long prevalent period. On the other hand, the late 1960 cohort group had a short latent interval and a short prevalent period. Of 535 study subjects with VWF during the 20 observation years (prevalence rate: 41.0%), the recovery rate was 38.9% on average from the time of cessation of exposure.
Published Version
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