The trucker strain monitor: An occupation-specific questionnaire measuring psychological job strain

Objectives: To develop and validate a short and user-friendly questionnaire measuring psychological job strain in truck drivers. Methods: In cooperation with an occupational physician in the Dutch road transport industry we developed items on the basis of face validity and information of existing questionnaires on the subject. These items were pilot-tested, by means of interviews, in 15 truck drivers. Study I examined the factorial structure of the initial 30-item trucker strain monitor (TSM) in a sample of 153 truck drivers. Subsequently, number of items per factor was reduced on the basis of reliability analyses (Cronbach's alpha). Study II examined construct and criterion validity of the TSM in a randomly selected group of 2,000 truck drivers, of whom 1,111 participated (adjusted response = 63%). Additionally, sensitivity and specificity were assessed by examining the ability of the TSM to identify truck drivers with or without self-reported sickness absence in the past 12 months because of psychological complaints. Results: Factor analyses of the initial 30-item TSM revealed a two-factor solution. Item reduction resulted in a six-item work-related fatigue scale and four-item sleeping problems scale with high internal consistency. Results of study II confirmed the internal consistency of the TSM scales and provided support for construct and criterion validity. The composite, work-related fatigue, and sleeping problems scale had a sensitivity of 83%, 80% and 71% respectively, in identifying truck drivers with prior sickness absence because of psychological complaints. Specificity rates were 72%, 73% and 72% respectively. Conclusion: Despite methodological limitations, the results suggest that the TSM is a reliable and valid indicator of psychological job strain in truck drivers. In particular, the composite and work-related fatigue scale identified drivers with prior absenteeism because of psychological complaints, quite accurately. Future longitudinal research in specific sub-groups of truck drivers including both self-reported and objective psychological health measures should evidence whether (1) the distinction between two indicators of psychological job strain is useful, and whether (2) the TSM can be used in screening out truck drivers at risk of developing psychological health problems.