Occupation-specific screening for future sickness absence: criterion validity of the trucker strain monitor (TSM)

Background: Monitoring psychological job strain may help occupational physicians to take preventive action at the appropriate time. For this purpose, the 10-item trucker strain monitor (TSM) assessing work-related fatigue and sleeping problems in truck drivers was developed. Objectives: This study examined (1) test-retest reliability, (2) criterion validity of the TSM with respect to future sickness absence due to psychological health complaints and (3) usefulness of the TSM two-scales structure. Methods: The TSM and self-administered questionnaires, providing information about stressful working conditions (job control and job demands) and sickness absence, were sent to a random sample of 2000 drivers in 1998. Of the 1123 responders, 820 returned a completed questionnaire 2 years later (response: 72%). Results: The TSM work-related fatigue scale, the TSM sleeping problems scale and the TSM composite scale showed satisfactory 2-year test-retest reliability (coefficient r=0.62, 0.66 and 0.67, respectively). The work-related fatigue, sleeping problems scale and composite scale had sensitivities of 61, 65 and 61%, respectively in identifying drivers with future sickness absence due to psychological health complaints. The specificity and positive predictive value of the TSM composite scale were 77 and 11%, respectively. The work-related fatigue scale and the sleeping problems scale were moderately strong correlated (r=0.62). However, stressful working conditions were differentially associated with the two scales. Conclusions: The results support the test-retest reliability, criterion validity and two-factor structure of the TSM. In general, the results suggest that the use of occupation-specific psychological job strain questionnaires is fruitful.