Shift work, sleep and health among offshore workers. A longitudinal study.

The present projects comprise two studies of shift work in the offshore sector. Study1 consists of an investigation into the effects of shift work among 260 employees on one offshore installation. Subjective data on sleep, working environment and health w ill be collected as well as objective measures of sleep, circadian rhythm and vigilance. The prevalence of shift work disorder will be estimated. Shift workers with and without shift work disorder will then be compared on sleep data, markers of circadian rhythm (saliva melatonin) during different shifts as well as on measures of sleepiness (self-report and reaction time). Finally, the groups will be compared on different metabolic (cholesterol, insulin, triglycerids) and immunologic (interleukins, tumor-n ecrosis factor-alpha) parameters. Study2 is longitudinal with a time frame of 10 years. Workers (n=1000) in the offshore sector will receive an annual questionnaire comprising questions about sleep, circadian preference, health, working conditions, safet y attitudes and experience of accidents and near accidents. Blood samples will be taken of 500 of these every second year. These will be analysed for metabolic and immunological indicators of somatic health. The subjects will also be asked to give saliva samples for DNA-analysis of clock genes. The reproductive health of females in the sample will be registered. For a minor subgroup (n=100) sleep and circadian measures in terms of saliva cortisol/melatonin will be taken in order to estimate adaptation to swing shift both during summer and winter. The health of night and daytime workers will be compared on both subjective and objective measures over the 10 year period. The effects of shift work on reproductive health will in particular be investigated. Fac tors such as clock genes and circadian preference which is related to shift work tolerance will be identified. Adaptation to swing shift will be investigated both with subjective and objective measures.