Excess workload has been regarded as an important psychosocial factor at work in Japan. In particular, overtime work could reduce sleep time and consequently exacerbate both physical and mental health, while excessive sleepiness induces work-related accidents. This study aimed to investigate correlations between excess workload and sleep-related symptoms among commercial long-haul truck drivers. We conducted a self-administrated anonymous questionnaire survey of 2054 commercial long-haul truck drivers in a medium-sized city in northern Japan. 1385 replies were collected and 1005 replies from male workers (mean age 41.8 ± 9.0 years old) were examined. The questionnaire mainly consisted of questions of sociodemographic characteristics, working conditions, the Japanese version of the Pittsburgh Sleep Quality Index (PSQI) and the Japanese version of the 12-item General Health Questionnaire (GHQ-12). 33% of the subjects worked more than 80h per month in addition to their regular work. 34.6% mainly worked at night and 54.2% worked at night and during the day. 41.5% of the subjects replied that their work schedules were irregular. A multiple logistic regression analysis revealed that excessive sleepiness while driving was significantly associated with overtime work, working hour distribution (night dominant), irregular schedules and a GHQ-12 score. Similarly, an association between subjective sleep quality and overtime work, irregular schedules, habitual exercise and a GHQ-12 score was found to be significant. Sleep disturbance was significantly associated with body mass index, overtime work and a GHQ-12 score. © 2006 The Authors; Journal compilation © 2006 Japanese Society of Sleep Research.
