Subjective fatigue and stress hormone levels in urine according to duration of shiftwork.

To determine the associations between urinary catecholamines and cortisol and subjective complaints of fatigue in shiftworkers, we conducted a field survey of 113 male shiftworkers at a manufacturing company in South Korea from late October to late November in 1999. The shiftwork system in the company was the backward rapidly rotating 4-crew 3-shift, with the morning shift starting at 7:30 AM. Using a self-report questionnaire, we assayed demographic characteristics, past medical history and working hours, as well as subjective complaints of fatigue in 3 categories of questionnaire. We found that, among workers with less than 5 yr of shiftwork experience, the concentrations of norepinephrine, epinephrine (Epi), and dopamine during the afternoon shift were positively correlated with Set II (difficulties in concentration) and Set III (projection of disintegration) of subjective fatigue symptoms. In addition, Epi concentrations were positively correlated with Set I (drowsiness and dullness), II, and III of subjective fatigue symptoms during the night shift. However, among workers with 5 or more years of shiftwork experience, there was no significant positive correlation between urinary catecholamine and subjective fatigue symptoms. In the long term shiftwork experience group, only the complaints scores of Set II fatigue symptoms (difficulties in concentration) during the morning shift were significantly higher than those of the short-term shiftwork experience group within the same shift.