Long-term sick leave and disability pensioning due to back disorders of tractor drivers exposed to whole-body vibration

In a historical 11-year follow-up study, disability pensioning and the incidence of the first sick leave of 4 weeks or longer due to back disorders has been investigated in a group of drivers exposed to whole-body vibration (WBV), mainly of agricultural tractors. The reference group comprised workers not or only slightly exposed to WBV from the same and another company. The vibration exposure of the tractor drivers was roughly around the ISO-2631 fatigue-decreased proficiency limit. The incidence of a first long-term sick leave due to back disorders was 3 per 100 person-years in tractor drivers and 2 per 100 person-years in the entire reference group. However, the incidence was not substantially increased in tractor drivers when the referents comprised only those working at the same company, suggesting selection bias. The highest relative risk (ca. 3) was found for long-term sick leave due to intervertebral disc disorders and this risk seemed to increase with the received WBV dose. That especially the incidence of intervertebral disc disorders increased, agrees well with findings in other studies. Data on disability pensioning due to back disorders are too scarce to be conclusive, but a trend towards younger disablement in tractor drivers is evident. Exposure to WBV, together with twisted posture and prolonged sitting, are considered to be responsible for the increased incidences observed in tractor drivers