Abstract
We investigated the immunity and the main factors that affect the immune system of 19 truck drivers as the experimental group and 27 office workers as the control group at a transit corporation in Tokyo; all subjects in both groups were examined through an assay of NK activity and NK subsets before and after work. At the same time, they were asked to complete a questionnaire on their working hours per day (WHPD) and driving hours per day (DHPD), in addition to the Health Practice Index (HPI), Self-Rating Depression Scale (SDS), Stress Tolerance Check List (STCL), and Symptom Checklist (SCL). The results obtained were as follows:
1. Before work, no difference was seen in NK activity between the experimental group and the control group, with both groups showing E:T ratios 5:1 to 20:1. After work, the NK activity (E:T=20:1) of the experimental group was significantly lower than that of the control group.
2. In the experimental group, the NK activity and NK subsets (CD3-CD16+CD56+, CD3-CD56+, CD3-CD16+) of the peripheral blood lymphocytes after work were significantly lower than before work (p<0.05, p<0.01, p<0.01). After more than five driving hours, the value of the CD3-CD16+CD56+ subset was significantly lower than that after fewer driving hours.
3. Correlation coefficients were calculated based on the average value of NK activity (E:T=20:1), CD3-CD16+CD56+ subset, and WHPD, DHPD, and HPI in the driving group. NK activity (E:T=20:1) and DHPD were found to be negatively correlated (r=-0.28), as were the CD3-CD16+CD56+ subset and WHPD (r=-0.43) and the CD3-CD16+CD56+ subset and DHPD (r=-0.63). On the other hand, NK activity (E:T=20:1), the CD3-CD16+CD56+ subset and HPI were found to be positively correlated (r=0.41 and 0.33).
