The present project combines an experimental and an epidemiological approach to study whether sleep deprivation, as it is practiced in non-daytime shift-work, is associated with health complaints. The principal objectives of the proposed project are i) to identify the effect of experimental sleep deprivation on pain, ii) to identify the effect of shift work on sleep and health complaints and iii) to identify the effect of shift work on health complaints. Participants will be recruited from nurses at Hospital from all across Norway.