Sleepiness in Spanish nursing staff--influence of chronotype and care unit in circadian rhythm impairment: research protocol.

Aims: To determine how prevalent circadian rhythm impairments are in nurses working in medical, surgical and intensive care units in five Spanish hospitals and how the quality of night-time sleeping and sleepiness affect the nurses' morning and evening chronotypes.

Background: Shift work is a recognized work pattern for nurses in all countries. Given the important role that nurses play in hospital care, it is vital to establish what repercussions this has on the nurses' working schedules and how any disturbance in circadian rhythm affects patient safety.