Do maritime crew members have sleep disturbances?

Data obtained from surveys of two samples of maritime crew members were studied for differences in self-reported sleep lengths and sleep problems. The data addressed both on- and off-duty variables. Statistical analysis of the data found that on-duty sleep length was shorter than off-duty sleep length for both groups. The two groups' responses to various sleep-problem items were significantly different. Most responses were below the scale mid-point. The differences between on- and off-duty sleep-problem items were not significant. Following a factor analysis, selected sleep-problem items were combined to form a composite Sleep Disturbance Scale. Using this composite measure, the correlation between the composite and sleep length was not significant. Overall, the results indicate that caution should be exercised before labeling shift workers as having "disturbed sleep" or suffering from "sleep disorders." The results do confirm the previous findings that shiftwork reduces sleep length on workdays.