Health conditions of bus drivers in a 6 year follow up study.

The bus drivers of a public bus company, working in a fast rotating 4 shift system from 05.00 to 24.30, were examined in 1993 (230 persons) and 1999 (266 persons). The comparison between the two years showed no significant differences for all the parameters evaluated by the Standard Shiftwork Index and medical examination. In both surveys work organisation was considered "efficient-fairly good" by most workers, who were mostly satisfied with their job. Work load was rated significantly higher for "afternoon" and "morning" shifts, during which most accidents at work and "in itinere" occurred. Night sleep was reduced by 3 hours on "early" shift and about 2 hours on "morning" shifts. The most prevalent health troubles dealt with low back pain, gastritis, headache and haemorrhoids. Neuroticism was the trait more correlated with poorer health conditions, whereas shiftwork exposure appeared as a significant predictor of risk of critical Effort/Reward Imbalance and minor psychological disorders. Both extrinsic and intrinsic efforts significantly increased with age, but not reward. The comparison of the same cohort of 108 persons examined both in 1993 and in 1999 showed a significant increase of low back pain, gastrointestinal troubles, haemorrhoids and lipids disorders.